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Proyecto de Construcción: Casa "La Esperanza"

Información General

On this page, I offer a guide to building a house in Mexico, which you should read to avoid making expensive mistakes in your own construction. This guide is based not only on observations and general research (in particular, on earthquake-resistant construction), but also hands-on experience from my own two construction projects. These are:

"El Refugio"
my first house construction, built in 2006-2007 through an architect.
"La Esperanza"
the subject of this website, built 8 years later with myself as architect.

Both are good-quality (and legal!) constructions, that illustrate how a house should be built (where things have not been done properly, I have called this out).

KEY

1 The Pros and Cons of Self-Building

There are some major advantages in building your own house in Mexico. Nonetheless, building a new house tends to be riskier than purchasing an existing one, and this is certainly true without proper research, planning, and preparation. The criteria also depend on whether you will be hiring an architect, or managing the construction yourself.

This page helps you to maximize the pros and minimize the cons. But to do this, it is necessary to correct some of the ignorant beliefs propagated on the internet, primarily by those from North of the Border (NoB). These, combined with their unshakable faith in their own superior knowledge (and thus being led by others from NoB instead of respecting the practices in Mexico), have resulted in numerous structurally dubious and illegal constructions.

Few want to tell you about disasters of their own creation (which are likely to transpire only long after the construction is completed), only their apparent successes. I offer you some hard facts and impartial advice to enable you to build successfully and enjoy your new house for many years.

2 Basic Construction Techniques (Masonry)

Anyone embarking on building a home in Mexico ought to have a basic understanding of the techniques employed. These are likely to be completely unfamiliar; in particular, the predominant construction type (confined masonry wall) is quite different from the lightweight timber framing used NoB. This goes some way to explaining why foreign house constructions in Mexico are often big on square footage and cosmetics, while being seriously deficient structurally.

Most of Mexico is earthquake-prone, especially the western parts closest to the subduction zone in the Pacific, and areas such as in Mexico City with poor ground conditions. Therefore, buildings must be designed to cope with stresses other than those due to gravity. In earthquake country, one must think laterally. Failures in masonry construction may endanger human life - and yes, there are regulations governing house construction in Mexico!

The form of masonry house most resistant to earthquakes is a simple rectangle, with smallish floor areas, limited doors and windows, and a flat reinforced concrete slab roof. This describes a typical Mexican house, but not one that is likely to be built by a foreigner. That is not to say that one cannot have a more elaborate design; however, this will call for more attention to structural issues. This requires the early involvement of a structural engineer, or at least an architect who is well versed in confined masonry wall construction (note that this is not used NoB).

In general, if the house is not built according to the practices normally employed in Mexico (and also in various other earthquake-prone countries throughout the world), one should ask why, rather than presume that one's own type of construction is superior. And if the construction develops defects, one should compare the way it has been built with that illustrated on this website, rather than blame Mexican masonry construction in general.

Those not happy with that "primitive" masonry construction should realize that timber framing will not be a good deal in Mexico; wood is more expensive, and being a niche construction type, design and implementation are likely to be questionable. But Mexicans (who are actually quite practical and balanced people) wonder why anyone would build a house of wood. Here are just some of the advantages of masonry construction over timber framing:

Masonry construction potentially offers a much greater lifespan, requiring only superficial maintenance. Confined masonry with a reinforced concrete foundation also offers excellent resistance to earthquakes. However, there are issues arising from the use of predominantly brittle rather than flexible materials. And if a masonry construction does come down, it is more likely to kill you than a timber one. Hence the importance of building to accepted standards.

These include the use of reinforced concrete, which (unlike bricks, blocks, mortar, stone, and plain concrete) is ductile (flexible), not brittle in an earthquake. This material combines high compressive resistance with high tensile strength, and could well be used for the entire house structure. However, while this would offer rather better performance, it would add considerably to the cost. Hence it is typically used only for the roof and to improve the performance of walls. But a greater proportion of reinforced concrete tends to be better. And it is also important that all concrete in an element is poured on the same day, so that it forms a single cohesive unit.

Apart from the structural concerns, to maintain a comfortable inside temperature the house should have good thermal mass and/or insulation. In particular, a thin roof (less than 20cm) is likely to result in uncomfortably high indoor temperatures late in the day, while being unduly cool in the morning. But all masonry helps to keep an even indoor temperature by absorbing heat when it is warm, and releasing it when it is cool. And a greater mass of masonry yields a greater degree of temperature stabilization.

This section covers the three basic structural components: walls, the foundation, and the roof/intermediate floors. All three areas are subject to flimsy and inadequate implementations by foreigners, probably through a tendency to cling to what they are familiar with.

2.1 Walls (Confined Masonry)

In plain masonry wall construction, the walls (bricks/blocks and mortar) are load-bearing, and have no other structural elements, except additional support such as a lintel or arch over doors and windows. This is appropriate in areas without significant earthquakes, where only compressive gravitational loads need be considered. However, while plain masonry is strong with compressive loads, it is weak with non-compressive ones.

Confined masonry is an enhanced form of plain masonry designed to avoid the brittle failure that can occur in plain masonry when it is subjected to the kinds of stresses that arise in earthquakes. As the term confined masonry implies, the idea is to confine sections of masonry wall between reinforced concrete tie-columns (castillos) and bond-beams (dalas). As the terms "column" and "beam" are likely to mislead, these will henceforth be referred to as "confining elements".

  • This is NOT framed construction!

In framed construction, the frame is built first, then infilled or clad for space partitioning (the frame bears all loads, including that of the infill). In confined masonry wall construction, the bricks/blocks and mortar are laid first, then the confining elements placed around them to confine the areas of wall within.

The basic design principle is quite simple:

Note that since the bricks/blocks and mortar are the primary load-bearing elements, any openings (doors/windows) will to some degree weaken the structure, and so there is a limit to the acceptable density of such openings. There is also a limit to the acceptable wall density in relation to the floor area (for example, the walls in a one-story structure in the state of Guerrero must cover no less than 2% of the total floor area). Multi-story structures must have a substantially greater wall density, and especially avoid weak lower floors with low wall density, as are often designed by architects after client requirements.

The design does not require the confining elements to have any ability to resist compressive forces. It should be clear then why the idea that the bricks and mortar are merely infill is a dangerous one. Two cases of this delusion I have seen in houses built by architects from NoB are:

Note that when it is necessary to employ structural reinforced concrete columns and beams, they are known as columnas and trabes respectively, to distinguish them from castillos and dalas, and will normally be more substantial. Nonetheless, dalas are usually also used as headers for doors and windows - it is therefore usual to have the tops of all doors and windows at the same height.

The basic purpose of confining masonry walls is to prevent them from cracking and coming apart when subjected to the non-compressive forces that may arise in an earthquake. But there are several other big advantages of confined masonry over plain masonry:

Confined masonry is a relatively recent type of construction, the basic technique having been around for only about 60 years, and refined over that period. Although significantly more costly than plain masonry, confined masonry is considered essential in countries such as Mexico, and is used for even the lowest-cost masonry.

Apart from Mexico, it is used in Europe (Italy, Slovenia, Serbia), the Middle East (Iran), Latin America (Colombia, Chile, Peru, Bolivia, Argentina, Costa Rica, El Salvador) and Asia (China, Nepal, Indonesia). Anyone looking at photos of the disaster that occurred in Nepal on 25 April 2015 may note confined masonry buildings standing intact next to completely collapsed buildings of other construction.

Click here for a non-technical brochure from the Confined Masonry Organization, and here for a more technical document (in English) from the Institute of Engineering, UNAM, Mexico.

2.1.1 Confining Elements (dalas and castillos)

This section deals primarily with dalas and castillos; however, trabes and columnas are made in just the same way.

The elements of the steel reinforcements are:

varilla
rebar made of mild steel; for houses normally either 1/2" or 3/8" diameter
alambrón
more rigid steel, made into a collar to space out the varilla; usually 1/4" diameter
alambre quemado
tempered steel wire, used to tie the rebar to the collars

The collars should normally be applied every 15cm. There must be sufficient high-grade concrete around the steel to properly support it, and thus provide the synergistic interaction characteristic of reinforced concrete. The required compressive resistance of the concrete is normally specified as 200Kg/cm2, and the tensile strength of the varilla as 4,200Kg/cm2.

This is a close up of the reinforcements for a largely decorative circular column of "El Refugio", showing the three types of component (varilla, alambrón, and alambre) assembled.

In this case, six varillas of size 3/8" are used. Reinforcements come in various shapes and sizes; typically those used for house construction contain from 4 to 8 varillas, each of either 3/8" or 1/2" diameter.

There are three processes involved in making dalas and castillos (and also trabes and columnas):

1. armado
assembly and fitting of the steel reinforcements
2. cimbrado
fitting wooden boards to form the concrete
3. colado
mixing and pouring the concrete

Generally, the sizes and positions of the confining elements (as with other aspects of this informal type of construction) are rule of thumb, and in practice depend on how substantial or economical is the construction. However, there are a number of guidelines.

Castillos in Mexico must be no more than 3m apart, although this regulation is frequently violated, and in other countries the maximum spacing is 4m. With low walls (and thus less area to confine), a greater distance than 3m may be acceptable. With a simple wall (e.g. boundary), castillos should be equally spaced; however, this will not normally be the case within a house, where there are intersecting walls and other considerations. There must be a castillo at each wall intersection to connect the walls. Stronger castillos should normally be used for outside corners as, apart from connecting walls, these bear the greatest stresses.

Dalas are of three types:

dala de desplante
This is placed around ground level on top of the foundation, and must be treated to prevent rising damp.
dala de cerramiento
This is placed at about 2.1m above floor level in normal house walls. This is the height for the tops of doors and windows, and (apart from confining the wall section) also serves as the door/window header.
dala de coronación
This is placed at the level of the intermediate floor or roof, and also enables connection of the roof/floor slab to the wall.

Where an elevation contains no door or window openings (such as a side wall with adjoining lots) and the floor height is no greater than 3m, the dala de cerramiento may be omitted.

There should also be confining elements (dalas and castillos) around any significant openings, such as for doors or windows.

The completed dala de cerramiento with the dala de coronación under construction on the living room of "El Refugio". The dala de desplante can also be seen on the foundation wall (with evidence of damp-proofing).

On the extreme left is a columna rather than a normal castillo, to compensate for a wall discontinuity (an alcove).

2.1.2 Wall Sections (bricks/blocks and mortar)

These are the areas within the confining elements, and comprise bricks or blocks bonded with mortar. For good adherence in hot and dry weather, these materials should be wetted before being laid.

Bricks in Mexico are usually flat (without recesses). Standard bricks measure roughly 23cm x 12cm x 5.5cm (length x width x height), but both larger and smaller sizes are available. A single-thickness wall is based on the width of a standard brick.

For greater compressive resistance and stability (and also greater thermal mass and sound isolation), thicker walls are used. The next thickness up comprises a brick width plus a brick height (1½-thickness); double-thickness walls use two widths of brick.

1½-thickness and single-thickness walls under construction at "La Esperanza". The finished thicknesses are 25cm and 18cm respectively (consistent with a 3cm layer of aplanado each side and a 1.5cm layer of mortar). The 1½-thickness walls not only provide a stronger structure, but also give a more even internal temperature than single-thickness walls.

In the background can be seen the boundary wall, made of concrete blocks with a thickness of 15cm.

Double-thickness walls being built by the entrance of "El Refugio". These are used only in this area to compensate for the lack of wall density due to the double entrance doors and large open space behind.

Concrete Blocks are of heavy solid concrete (not to be confused with lightweight blocks of similar appearance). They are normally of a larger size than brick (typically 28cm x 15cm x 11cm). They should always be used for foundation walls, as they give better resistance to damp than brick, as well as good compressive resistance. We also used them for the boundary wall of "La Esperanza" to give a stronger result without requiring two layers of brick.

Cinder Blocks are of lightweight materials, and give less compressive resistance than normal brick or block. They are used where low mass is more important than strength (for example, on an upper floor to reduce the load, or where the material is infill rather than structural).

Hollow Blocks are of various types; these offer less structural strength than solid materials. However, thicker walls made of hollow materials may be appropriate where good thermal insulation is required.

2.1.3 Cladding (aplanado plus finishes)

Walls are covered with 2-3cm of a stucco-like material known as aplanado. This is applied in two layers; a rough first coat, then a second fine one that is smoothed to a very even surface using a long metal bar. On this is applied sealant, then the final finish (bare aplanado is dark and unattractive). Typical finishes are texture (used to emboss in a variety of patterns) and paint, or wall/floor tile.

Because cladding is of mainly cosmetic value, adds significantly to the cost, and finishes are prone to wear and tear, walls are often left unclad. The bare obra negra of coarse brickwork and confining elements usually lends the construction an ugly appearance. However, in some cases, these are made in a more refined way to give a presentable result.

The unclad wall over the storage room at "La Esperanza" has been made so as to achieve a presentable result without cladding. Other walls in this photo are finished with colored texture (thus avoiding paint); those to the left have a textured finish, while the wall to the right has a smooth finish.

2.1.4 Shrinkage Cracks

These frequently appear in the walls of a new construction, and result from the materials drying out and consequently contracting. It seems appropriate to mention this matter here, as those unfamiliar with masonry wall construction may be alarmed at these appearing in their new home, especially as the cracks can go right through the walls.

Shrinkage cracks have the following characteristics:

You can rest assured that these cracks are quite normal, and the issue is cosmetic only (remember that the bricks/blocks and mortar are only meant to bear compressive loads). Indeed, an absence of shrinkage cracks may indicate that the materials were not properly wetted before being laid. However, they can spoil finishes, and in particular cause wall tiles to crack. So it might be a good idea to wait for the cracks to appear before finishing the walls (although this may not be a convenient or attractive option).

2.2 The Foundation (Reinforced Concrete or Rock)

This is another area in which even high-priced house constructions are often substandard through ignorance and/or cost cutting. In a number of house constructions I have seen, there appears to be little or nothing that could reasonably be described as a foundation, with little or no excavation.

2.2.1 Soil and Excavation

Excavation to a significant depth is likely to be needed to reach a satisfactory base for the foundation. If there is any doubt as to how deep the foundation must be, a soil survey should be done.

Commonly-encountered black organic soils pose a particular problem. This soil type expands when wet (in the rainy season), and shrinks and cracks when it dries (in the dry season), and as such is highly unstable. One can only hope for a more stable mineral layer underneath (as with "El Refugio" at a maximum of 1.3m below the surface), or that it is sufficiently compacted at depth (as with "La Esperanza" at 1.8m down).

One must also beware of soil that is problematic in an earthquake. Certain types of clay and sand are thixotropic (they liquefy with movement). Much of Mexico City is built on unstable lake sediments that amplify seismic waves; as a result it suffers worse effects than many areas that are much closer to the epicenter.

The foundation of "El Refugio" sits in a stable mineral layer beneath the organic soil, as shown clearly by its lighter color. This should provide excellent resistance. It required excavation to a depth of about 1.4m, to ensure that all surfaces were within the mineral layer.

Trees should be located well away from the foundation (perhaps many meters). Apart from the obvious issue with roots, they extract substantial quantities of water from the soil, thus rendering it unstable with a consequent risk of undermining the foundation.

2.2.2 Structural Integrity

Furthermore, structural integrity in earthquakes must be considered. Seismic waves result in lateral compression and shear forces in the ground that must be resisted and/or absorbed by the foundation. Poor performance will jeopardize the entire structure of the house. For best earthquake resistance, there must be good connections not only between the foundation and the house, but also between elements within the foundation. So the foundation should function as a single cohesive unit.

Good structural cohesion can only be achieved by a reinforced concrete foundation, as employed for the houses of "El Refugio" and "La Esperanza", and illustrated in the photos above and below. The whole foundation is connected by means of contratrabes, and where appropriate, cadenas. The contratrabes (but not cadenas, which do not support walls) sit on zapatas corridas, which in turn sit on a continuous plantilla (a 10cm-thick base of "poor" concrete). This is likely to require a complete excavation of the area.

All concrete used in the foundation base must be poured on the same day, so that it sets as a single piece. This will probably mean hiring extra workers for that day, or else using a pumper truck.

The foundation base for the house of "La Esperanza" required over 51m3 of concrete, and we hired 20 additional workers that day (to give a total of 30). Here, the molds are being removed the day after the pour. In the center of the photo is a cadena; this does not support a wall - its purpose is to provide proper lateral connection.

Also shown is the rock foundation for the boundary wall. Both have a depth of 1.8m, but the rock foundation developed numerous structural defects, which were remedied in part by using the house foundation. We believe that these were due to poor implementation (laying of the rocks and/or insufficient concrete), as the soil resistance appears to be sufficient at this depth. Nonetheless, they illustrate the problems that may arise with this type of foundation, and we regret that the boundary wall does not have the same foundation as the house.

2.2.3 Rock versus Reinforced Concrete

Unfortunately, a reinforced concrete foundation is expensive (that for "La Esperanza" cost about M.N.$550,000 in 2014, of which about 2/3 was on materials). So for economic reasons, the most common type of foundation for Mexican housing is a rock one. Here, trenches are dug for wall footings (typically to a depth of 90cm, which may be insufficient). Each castillo sits on a separate zapata, which again is supported by a plantilla. These and the trenches in between are filled in with rocks and concrete.

Remedial work on the rock foundation of the fachada of "La Esperanza". It shows that in a rock foundation, each castillo has its own separate plantilla and zapata, with no ties between them (contratrabes on zapatas corridas, and possibly cadenas), only rocks and concrete.

Although cheaper, a rock foundation lacks structural integrity. Comparing a reinforced concrete foundation to a rock one is somewhat analogous to a comparison of confined masonry walls with plain masonry. With the former, all elements are tied together and thus resistant to external stresses. Also, the reinforced concrete is flexible in an earthquake, and allows seismic forces to be absorbed. By contrast, rock and concrete is apt to crack and come apart, thus compromising the foundation and everything above it. The static resistance of a reinforced concrete foundation also benefits from its structural unity, and will tolerate a lower soil resistance. A rock foundation becomes less viable as foundation depth increases.

Nonetheless, the majority of houses in Mexico have a rock foundation, and the choice of foundation type is likely to be a matter of how high one wants to set the bar. A properly-implemented rock foundation should be satisfactory if the expectation is a lifespan of say 30-50 years without major faults developing. But if you want a house with a good chance of lasting centuries without significant structural issues, you should consider investing in a reinforced concrete foundation, especially in an area prone to earthquakes or with poor soil.

2.2.4 Damp-proof Membrane

This is to prevent rising damp (moisture from the soil penetrating up the walls by capillary action). It is laid on top of the dala de desplante, and normally consists of a sheet of asphalt covered with black impermeabilizante (this used to be tar, but now synthetic materials are used).

The damp-proof membrane applied to the foundation of the house of "La Esperanza".

As must always be the case, the foundation walls are made of dense solid concrete blocks, as these provide better damp resistance than brick. All these cavities will be filled with gravel and sand to make the floors.

2.2.5 Lower Floors (compacted sand/gravel plus firme)

This section covers only floors at the lowest level (basements are not common in Mexico). Upper floors are covered in the next section.

These are based on a good depth of a stable material like filtro. Toward the top is predominantly sand and fine gravel, with the surface being of sand. This is soaked with water and compressed with a compactador so that it is rock-hard. On this is poured the first rough layer (8-10cm) of firme. Before tiling, a second fine layer (2-4cm) of firme is poured; this must be carefully leveled and smoothed.

Floors at "La Esperanza", some with firme already poured, others of compacted gravel and sand ready to receive the first layer of firme.

For this construction, a complete excavation was done, and the filtro extends to the base of the foundation. 518.4m3 of this was compacted in 40cm layers with a compactador to give a stable floor base. It is a lamentable fact that at $320 rental per day, this machine was more highly-valued than an albañil; but its use is necessary to properly compress the material.

The living room floor of "La Esperanza" with the second layer of firme being applied prior to receiving the floor tiles.

Before laying the floors, plumbing must be installed by an experienced fontanero, who should be involved and consulted well before construction starts (this consultation should also cover infrastructure requirements such as a cistern and septic tank). Be suspicious of a maestro who claims competence in this area also.

2.3 Structural Roofs and Upper Floors (Losa or Bóveda)

This section deals with structural masonry roofs, as are used in the majority of houses in Mexico. Nonstructural roof types include steel/plastic/asbestos sheet and palapa, but these serve only to keep the rain or sun out, and would not be used for the main areas of a quality house. There are also timber roofs/floors, but these are seen mainly in older buildings (reinforced concrete was introduced only around the turn of the 20th century).

The structural criteria that apply to roofs also apply to upper floors (only the topping is different); so flat structural roofs and upper floors are essentially the same thing. On many houses, you can see stubs of castillos, left so that another level can easily be added; the previous roof then becomes an intermediate floor (entrepiso).

I describe here the two types of structural roof generally considered suitable for use in earthquake-prone areas. These are:

2.3.1 General Features

Either type of roof may be either flat or sloping (the term dos aguas is used for double-sloped roofs). The majority of structural roofs in Mexico are flat, although these are actually slightly inclined in possibly more than one direction to allow proper drainage (the required drainage patterns should be specified in the roof plan). Where roofs are visibly inclined, the slope is often very slight (only a few degrees).

More steeply inclined roofs tend to be unstable in an earthquake, and you should check the regulations that apply in your area before incorporating such roofs into plans; for example, that the maximum allowed slope is not exceeded. To prevent problems in earthquakes, one should in general avoid top-heavy construction. Another feature requiring careful consideration is overhanging floors (cantilevers). Although these are commonly used, they tend to compromise performance in earthquakes; numerous factors must be considered to determine what degree of overhang is acceptable.

Apart from structural criteria, there is the matter of thermal mass, which stabilizes the internal temperature. While all masonry contributes, the roof is of fundamental importance, due to its high exposure to sunlight. Where there are large night/day temperature swings, the minimum thickness of masonry required to avoid heat coming through late in the day and being lost overnight is about 20cm. This should also provide excellent structural strength and sound isolation. However, in some areas it may be better to reduce the thermal mass, and instead add thermal insulating material.

Flat roofs of both types are finished off by tiling with baldosa, on which cement with sealant is applied. This is then painted with impermeabilizante, which must be renewed every few years. This is either white or dark red, and the two colors clearly have different properties in reflecting or absorbing sunlight. Although white reflects more visible light, the dark red impermeabilizante is often said to keep the house cooler, as it radiates back more heat (infra-red light). Flat roofs may alternatively be finished with floor tile (this of course would be the norm for an intermediate floor).

Inclined roofs are first sealed, then impermeabilizante is applied (there is no baldosa; however, this type of roof should eliminate water pooling). Decorative clay roof tiles are then often cemented on top. While these are mainly cosmetic in function, they protect the impermeabilizante from the sun and most of the rainwater; as a result it should last much longer. The downside is that, if and when it does need to be renewed, the tiles will make this job more difficult. Roof tiles may also help to keep a cool and even interior temperature, especially those with a significant air space underneath.

2.3.2 Losa (Reinforced Concrete Slab)

This is by far the most common type of structural roof for houses in Mexico. It is usually flat, but may be inclined to varying degrees. It is typically about 20cm thick, with a minimum thickness of 8-10cm.

The first stage in building the roof is cimbrado (fitting of wooden boards to support the roof). These are supported by wooden posts, and provide a level (or sloping, if required) surface.

Underneath the roof of "La Esperanza", showing the posts and boards used to support the concrete while it hardens.

The next stage is armado (assembly of the steel reinforcements). These consist of a substantial quantity of varilla laid out in a grid (like steel mesh); the vertical/horizontal intersections of the lengths of varilla are tied with alambrón and alambre. There may be several layers, depending on the thickness of the losa. This is tied to the dalas de coronación that sit on the tops of all walls (internal and external), which in turn are tied to the castillos.

The flat parts of the roofs of "La Esperanza" after fitting the wooden boards and some of the dalas de coronación, but before reinforcing with varilla. To the right can be seen some of the alambrón that will be used to connect the varilla. The blocks are to leave spaces for the skylights. At 30cm, this losa is thicker than usual, and will be reinforced with over a tonne of varilla. In fact, over the losa is a layer of firme, giving a total thickness of 40cm; this goes some way to explaining why the interior temperature remains so constant 😃

The final stage is colado (mixing and pouring the concrete). To ensure its structural integrity, the concrete must all be poured on the same day so that it sets as a single piece. Hence it will usually be necessary to either hire additional workers for that day to do a roof pour, or else use a pumper truck. Contrary to popular belief, this is not done just to prevent leaks; these can easily be dealt with when applying the topping.

Baldosa being laid on the rear flat roof section of "La Esperanza".

A losa at least 20cm thick should give good thermal mass and structural strength, as discussed above. However, it may in some cases be appropriate to use a thinner losa. This would be used on a small and economically-built house, but might also be used on a quality house where insulation is important.

Structurally, the minimum viable thickness of reinforced concrete is 8-10cm, and this may be appropriate in areas where air conditioning or heating are required. Here, thermal insulation is likely to be more important than mass, and this minimal slab can be combined with insulating material (normally styrofoam with steel mesh). With this type of roof, care must be taken to ensure that its strength is sufficient.

2.3.3 Bóveda (Brick Arches and Beams)

This type of roof construction consists of brick arches between beams. It is a traditional roof type, most common in the western state of Jalisco. It was used almost entirely for "El Refugio", and for the sloping roofs of "La Esperanza".

There are two basic types of bóveda:

de cuña
thick bóveda (based on a brick width) used for the intermediate floors and flat roofs of "El Refugio"
catalán
thin bóveda (based on a brick height) used for the sloping roofs in both "El Refugio" and "La Esperanza"

For both types, the beams must be no more than 1 meter apart, and the arches should have a height of at least 10cm. The arch principle distributes the weight outwards, and provides good structural strength. However, the static resistance required of the supporting beams should not be underestimated, and is increased substantially by long spans (it is advisable to refer to span tables).

For "El Refugio" and "La Esperanza", steel I-beams of size 6"x4", 8"x4" and 8"x5¼" were used. These are priced per kilogram, and beams of the same dimensions may differ in weight per meter. The 6"x4" beams used for "La Esperanza" are of two grades; the thinner grade (12.7 Kg/m) was used for spans of up to about 3.2m, and the thicker one (17.9 Kg/m) for the three spans of about 6.5m. For "El Refugio", with its predominantly de cuña bóveda and generally longer spans, heavier grades were used; the 8"x5¼" beams weigh in at 28.58 Kg/m.

Construction of the de cuña bóveda over the entrance hall of "El Refugio". The brick arches are laid between 6"x4" beams, which are welded onto an 8"x5¼" beam running the depth of the house (this is supported at various points, so the spans are not excessive).

The bricks should be of a higher quality than those used for walls, for both structural and cosmetic reasons (bricks for bóveda will normally be fired at a higher temperature). Laying the bricks is done using specially-made wooden molds on posts to form the arches; these are left in place until the mortar has hardened.

The roof or floor surface is then filled in and topped with reinforced concrete, to give a result with the same appearance as losa. To do this, the roof is covered with steel mesh and varilla, which are welded on to the tops of the beams. Then several centimeters of concrete are poured (thus filling in all the indentations around the beams).

Unlike with losa, there is no structural need to pour the concrete as a single piece, and it is usually applied in separate sections. However, this is likely to lead to cracks; so to provide good waterproofing on inclined roofs, the impermeabilizante should be applied in conjunction with membrane. This should not be necessary for flat roofs, to which baldosa with cement and sealant are applied.

Topping of the sloping catalán bóveda over the rear of "El Refugio". As can be seen, the concrete is applied in sections (not as a single piece). As this is an inclined roof (without baldosa and sealant), membrane must be used with the impermeabilizante to prevent leaks due to cracks in the concrete.

The catalán bóveda used for the inclined roofs of both "El Refugio" and "La Esperanza" has a finished thickness of about 20cm, before fitting the cosmetic tiles. The finished thickness of the de cuña bóveda of "El Refugio" is 30-40cm. This goes some way toward explaining its reputation for being remarkably cool in spring.

A considerable amount of internal finishing work is required to achieve a good cosmetic result, including refining the mortar work, cleaning, filling in any I-beam gaps with cement, and painting. In any case, the appearance will be "rustic", but perhaps more attractive in many situations than the usual flat ceiling. Apart from this, the irregular rather than flat surface should give better acoustics (without flutter echoes).

Finishing of the catalán bóveda of the living room ceiling in "La Esperanza". The beams are 6"x4", set into an 8"x4" beam of the lightest grade at the apex (this in fact is a secondary beam, supported by the 6"x4" primaries). Cement has been used to fill I-beam gaps, some of which has been painted. The brickwork remains in need of cleaning and finishing.

3 Permissions Required

For the construction to be legal, foreigners must get permission to:

  1. Buy Land: this must be privatized with title (escritura).
  2. Build: this requires detailed architectural and structural plans, plus structural calculations.

There seems to be considerable laxity in enforcement of regulations in Mexico. Development on ejidal land is by no means uncommon. Squatters' rights are strong in Mexico, and there is generally a sympathetic and tolerant attitude towards the poor. There are many basic houses built by the poor on illegal land; and these were clearly not built with permission on the basis of structural plans.

However, taking advantage of this easy-going situation as a (well-off) foreigner is not recommended. Although minor transgressions are unlikely to have any serious repercussions, evidence indicates that if you show contempt for the authorities by completely illegal construction, you may get away with it for a while, but sooner or later the authorities catch up with you. Then you will be blacklisted, and you will never get them off your back.

If you build on legally-purchased land, you will have full rights to your land and construction; if you do not, you will have none, and the authorities can seize the land or impose penalties as they see fit. Houses built by foreigners will be a good deal more substantial than the small and simple shacks put up by the poor; and if these are built without proper plans as required to get permission to build, they are not only illegal, but are likely to be structurally seriously substandard and even dangerous. So do not emulate poor Mexicans!

3.1 The Land

Non-Mexicans can own up to 1000 Hectares (about 2500 acres) of privatized land outside restricted zones, but must obtain permission from SRE for each land purchase (including land with existing construction). Mexican citizens are not subject to these restrictions, and do not require permission to buy land.

3.1.1 Restricted Zones

These are areas within 100 km of a national border, or 50 km of a coastline. For reasons of national security, non-Mexicans may not own land in these areas.

Instead, an arrangement similar to a leasehold is available, whereby a Mexican institution (such as a bank) owns the land, and the would-be purchaser derives rights to the land through this institution. There are significant annual fees involved in this, and some restrictions in what land can be "purchased" in this way.

3.1.2 Ejidal Land

Nearly all land outside urban areas is ejidal. Such land is actually owned by the government, which has granted an inalienable right of use to its landholders. This right of use is usually for agriculture, and does not permit construction, except for special purposes related to the designated land use.

Transactions involving ejidal land are common, but bear in mind that the terms "buy" and "sell" are misleading, as the government retains ownership and determines the land use. It has become possible to privatize such land so that it may be legally built on, but the permissions for this and subsequent change of use are at the discretion of the government, and not typically granted.

It is the government that determines how land is used. Many people would like to privatize ejidal land, as it would then be worth much more. But again, it must be emphasized that permission from the government to privatize land is discretionary, and unlikely to be granted for individual dwellings, only fraccionamientos where the government sees fit to develop the land. And even if the land can be privatized, the process is likely to be a lengthy one.

So, do not even think about buying land for your house unless it has a land title (escritura). If you do not get a clear affirmative answer to the question "¿tiene escritura?", look elsewhere. And if the answer is "sí", the seller should be happy to immediately show you at least a copy of the document.

3.1.3 Purchasing Land

This should be done through a notario público, who will carry out all the necessary checks and apply the law on behalf of both parties (it is not an adversarial system). One check is that there are no outstanding debts associated with the land, as the purchaser will inherit those debts. And the land must be privatized with a valid title.

As a foreigner, you will not be able to buy the land until permission has been obtained. Consequently, you will require a pre-sale contract between buyer and seller, which the notario público will also handle. This requires the payment of a substantial deposit (for "La Esperanza", it was about 25%).

To get permission to buy land from SRE, you will probably have to travel to the state capital. To avoid this trek for "La Esperanza", we paid the notario público extra to handle this on his next visit to Morelia.

3.2 The Construction

Before starting construction, both Mexicans and foreigners must obtain permission from the local construction office. This requires the provision of properly-drawn plans (in meters, not feet and inches!), plus structural calculations of loads and stresses that must be done by a civil engineer. There are obvious safety reasons for this, especially for masonry construction in an earthquake-prone region. However, the permission also supports the constructor in the event of any inconveniences caused to neighbors.

The permission to build the house of "El Refugio", from the municipality of Zamora, Michoacán. The architect (details obscured) obtained this document on my behalf, and there are errors in my name. There is a condition that a septic tank of capacity sufficient for the occupants be installed inside the property (this was omitted from the plans). We have a year to complete construction.

The permission to build the house of "La Esperanza", this time from the municipality of Jacona, and I was the architect as well as the owner.

There is a separate permission to build only a boundary wall, which requires only a simple plan. This would enable the boundary wall to be built early in order to secure the property, while the plans for the house are being developed. However, in our case (with the boundary wall being close to the house), it would have been better to have waited for permission for both wall and house, so that they were built on a common foundation (and by the same, much more competent, workers).

House plans submitted to the construction office must include both architectural and structural plans. The architectural plan must include a floor plan, sufficient elevations and cross sections to completely describe the form of the house, plus a map giving the location. Structural plans are required for the foundation, roof, and each intermediate floor. You can see my plans for "La Esperanza" here, and those for my first construction "El Refugio" here.

These plans would normally be drawn by the architect in conjunction with the structural engineer, who must approve, sign them and supply the structural calculations before they will be accepted by the construction office.

4 Managing the Project

Embarking on building a new house is exciting, and many might be tempted to rush into it without due preparation. But there is a great deal of money at stake, so it is well worthwhile to take some time to investigate and plan, to avoid mistakes and being ripped off. To this end, I urge you to read through the blog of my experiences building "La Esperanza", which presents many of the issues you should consider.

One of the first things to consider is whether to hire an architect (as I did with "El Refugio"), or (as we did with "La Esperanza") manage the construction yourself. Especially if you know a good maestro and fontanero, I recommend the latter course if at all possible. This will put you in full control of the project, can save you a great deal of money, and enables you to see exactly where the money is going.

But if you are going to hire an architect, you should read the next section carefully, as forewarned is forearmed...

4.1 The Role of the Architect

Most people will probably hire an architect to both draw the plans and build the house, as they would not feel confident to do either of these themselves. But even if you hire an architect, it is important to be familiar with Mexican construction techniques (read here). This will make you aware of what is reasonable and what is not, and generally reduce the architect's opportunities for manipulation and inappropriate construction.

Another reason for hiring an architect would be inadequate command of Spanish, and this is likely to lead you into the hands of an architect from NoB who has no understanding of Mexican house construction. I have already made clear the dangers of this, and you may be better off with a Mexican architect who speaks sufficient English.

4.1.1 Drawing Plans

A major stumbling block may be the inability to draw acceptable house plans. This will be the first task of the architect, after discussion with the client to determine the requirements (beware of being talked into accepting features that you do not need). However, the initial plans will probably be architectural only, without structural details.

The cost of the plans is often quite reasonable considering the amount of work involved, but this will be with a view to getting considerably more money from you later. So while it may be desirable to confine the architect's involvement to drawing the plans, the architect would probably not be willing to hand over structural plans that would enable you to obtain permission for construction and build the house yourself.

4.1.2 Managing the Construction

The architect will probably charge for managing the construction in one of two ways:

As you will see, neither scheme is without serious problems. Even more suspect would be a scheme whereby the architect charges for individual items of work on a piecemeal basis.

With a Fixed Percentage:

With a Fixed Price:

In Any Case:

4.1.3 My Experiences (A Very Brief Summary)

Having adopted the role of architect myself for this project, I found that the architect I hired for "El Refugio" was of very little value beyond the initial plans. It was our maestro Rubén who provided breakdowns of all the work, hired and paid all the workers, and generally managed the construction work; he clearly did not need the architect. On the contrary, the architect served only to lower Rubén's standards, and create resentment among the workers. There are numerous examples of abuse and plain stupidity by the architect, too numerous to mention here, but very costly.

Nonetheless, the architect appeared to believe me dependent on him to complete the construction, and halfway through attempted to force me into signing a contract that would guarantee he completes the house. This was after bad conduct on his part, not only to me, but even more to the masonry workers. I gave him an opportunity to continue if he mended his ways, but he misjudged me by forcing his contract under threats of stopping the construction, as I fired him on the spot. I managed to keep maestro Rubén and fontanero Jaime, even though the architect attempted to sabotage this and generally prevent me from completing the house. Incidentally, his "estimate" for the cost of completing "El Refugio" was MN $900,000; the actual cost was around MN $3,000,000.

Not being able at that time to speak much Spanish, it only became apparent to me when the architect left "El Refugio" just how much everybody hated him. The workers all lined up to see him off, staring at him on his way out through the gate, their hostility being very plain (you could cut the air with a knife). Normally strutting around, the architect's slumped posture was rather different at this humiliation (for me, perhaps the most satisfying point in the construction😊). I am not the only one who thinks that this guy is at the opposite end of the scale from a saint.

4.2 The Role of the Maestro

The maestro is key to the construction. He will:

To do this, he must also be able to read and follow detailed plans - one cannot reasonably build a house by word of mouth, nor as a piece of jazz improvisation... ♫

A good maestro will probably charge according to a book of standard prices for masonry work: Sindicato de Obreros Albañiles y Similares "Lázaro Cárdenas" (CROC). You should have a copy of this book, and I think it is reasonable to say that you should be prepared to pay these prices - no more, no less. You may well find people who will work for less, but a maestro of high reputation will be in demand and not prepared to accept lower prices. And as we have seen, you need to be careful to get the right maestro.

To be fair to "maestro" X, he charged significantly less than the Lázaro Cárdenas prices charged by Rubén. But as they say, you only get what you pay for - pay peanuts, get monkeys. If you hire said monkeys, you are likely to have to pay substantially more in the longer term in remedial work, and/or suffer a permanently unsatisfactory result. And the savings in the cost of labor may well be wiped out by greater materials costs, as good-quality workers use materials more efficiently. There is no doubt in my mind that had we hired Rubén for the phase 1 work, not only would we have a much better end result, but I would also have paid much less for it.

A maestro of good reputation will know the best people to hire for the job; and various skills are required with different people being appropriate for different jobs. The maestro will also be on site and in a position to closely supervise the work. You can then expect work of high quality, not the huge steaming pile of elephants' turds that "maestro" X left us.

Of course, you should always pay on the basis of work done, not by unit time. The best people not only do better work, they are able to do it more quickly, and would choose to work on a piece-rate basis. Paying hourly rates is a recipe for not only poor productivity, but also poor quality.

Payment for the work done must be made direct to the maestro each Saturday, in cash; failure to do this is a shameful breach of trust. Incidentally, masonry workers typically work from 08:00 to 17:30 on weekdays, with a break from around 11:00 to 12.00; on Saturdays they finish around 13:00.

Although the maestro will order materials as needed, you should normally pay for them yourself at the shop that supplies them. However, this may occasionally be impractical; then the maestro may pay for materials and provide receipts for reimbursement. But this should only be done for sundry items, not the main expenditure.

And, as with an architect, you must check what the maestro is doing. All labor quotes must be carefully scrutinized and understood; be prepared to haggle over prices that are not clearly defined in the union book. You must also check that the materials you are paying for are all going into the house (no siphoning off); again you should calculate the requirements and let your maestro know that you are doing so.

4.3 Other Workers

Apart from the maestro, you will also need a fontanero; typically one individual (and his team) will do both plumbing and electrical installations. All such installations must be done by the fontanero, not the maestro, with the exception of masonry work such as construction of the septic tank and cistern (and this should be done in consultation with the fontanero). Electrical and plumbing installations must be coordinated with the masonry work, so good communication between maestro and fontanero is vital (as is also the capability of the fontanero to read plans). It helped that our maestro and fontanero were good friends who had worked together on numerous constructions.

Steel beams must be fitted by suitably-qualified specialists (for obvious safety reasons); for our construction, the team fitting beams was hired by the maestro. Various other types of people will be required for finishing, depending on what is required; see the main blog for some examples.

Wherever possible, it is better to pay for materials and labor separately. The main areas in which this will probably not be possible are carpentry, aluminum/glass work, and some metalwork such as railings. Otherwise, avoid all-inclusive prices, as they tend to deprive you of transparency and choice, and will frequently result in your getting poor-quality materials for the price of good ones.

In general, expect to pay for materials in advance, and labor once the work is complete. This means that for areas such as carpentry where there may be a significant outlay to purchase materials, you will be expected to make a substantial downpayment. For large items of work, it is reasonable to pay for labor in parts, on say a weekly basis.

Your fontanero will probably buy the numerous parts needed for installations himself, but must give you all the receipts. You should provide a proper description of the installations required, to enable appropriate purchases to be made. Items such as sinks, taps, lighting, and fans are probably best bought yourself, although if you know what you want, the fontanero might also purchase these for you.

It is hard to overstate the importance of checking meticulously each item of work. However, this likely to be difficult, as those you contract tend to be adept at making the work look acceptable for the moment, only for it to fall apart when they are gone. Preferably you should check items while they are still under construction, but this will often not be possible. You will almost certainly not be offered any guarantee for the work; this ends with the payment.

4.4 Buying Materials

We had basic building materials delivered on a credit basis, with 15 days after delivery to pay. The maestro would order materials as needed, and we would pay for them on the Saturday after paying for the labor. In addition, we managed to get a price-match deal on cement, mortar and varilla after the owner of the shop we had been purchasing materials from to that point feared we would go elsewhere. Thanks to Verónica, who drives a hard bargain, we got rock-bottom prices on the main materials.

This supplier and various others offer discounts on listed prices; and what appears on the receipt will often be the full list price, significantly higher than what was paid. This fact can be used to the disadvantage of the end consumer, by architects and others charging the price given on the receipt and pocketing the difference. So it is better to pay for these yourselves where possible.

4.5 IMSS (Social Security) Payments

It is your responsibility to arrange for social security (IMSS) payments to be made for each relevant worker; this will certainly include the maestro and his team, although probably not the fontanero and others who work on a contract basis. In practice, it may be sufficient to pay IMSS only for the main workers (especially those exposed to the most risk).

It will normally be necessary to hire an agent to deal with IMSS, and the costs are not insignificant. But failure to make IMSS payments is not recommended, as again you may get away with it for a while, but pay for it later when you are blacklisted by the government. And not only is it reprehensible to fail to provide for the welfare of the people working for you, it may leave you facing substantial claims for compensation in the event of an accident.

5 Setting Up Home in Mexico

In this section, I give some information aimed at foreigners, especially that which is:

  1. relevant to the design or selection of a house
  2. likely to be unfamiliar to those coming to Mexico from other areas such as North America and Europe

It would therefore be a good idea to read this section before buying land or drawing up plans.

One should consider this paraphrase of a well-known saying: when in Mexico, do as the Mexicans do. Just as one should be suspicious of construction techniques not normally employed in Mexico, one should also consider generally that where things are done differently in Mexico, there is likely to be a good reason for it. But in some cases this reason is economic or due to lack of concern, and here you can aim for a better standard.

However, there are some areas in which a foreigner should take care to not fall short of the norm. Apart from construction quality, one of these is security. Houses in Mexico tend to be difficult to break into, featuring metalwork over windows and doors, steel doors, and often high boundary walls or railings. It is axiomatic that if your house is less secure than those around, that is what any burglar will go for! And private land without a secure boundary is likely to be taken as public property.

5.1 Infrastructure and Services

If you are from North America, Europe or another highly-developed area, you will see some big differences; generally the infrastructure is more basic in Mexico. However, it is usually possible to compensate one way or another, and the generally kinder climate tends to mean that you can manage happily with less.

This section does not cover services such as television, telephone, internet, and cable, for which it is difficult to provide generalized information. Specific details of these areas can easily be found using a web search engine.

5.1.1 Water

One of the first things you will notice on coming to Mexico is that each house has a water tank (known as a tinaco) on the roof. As far as I am aware§, nowhere in Mexico is water pumped at high pressure direct to the tap, and even in urban areas the supply may be discontinuous. Hence the need to store water in a tinaco. For a basic small house the capacity is usually 450L, but may be 1100L or more for a larger house.

By itself, this will yield only gravity pressure, which is generally less than ideal, and insufficient for a shower with fine nozzles. This is why showers in Mexico typically have "watering can" type shower heads. But this limitation can be overcome by installing a pressure system, comprising a pump and a pneumatic tank with manometer. This normally delivers water at a pressure of 45 pounds per square inch (although the pressure can drop to about half that before the pump activates to reflate the pneumatic tank). By comparison, gravity pressure is only about 1.4 pounds per square inch per meter of drop; so you will probably want a pressure system.

The pressure system of "El Refugio", shown during its construction. There is a separate pump to pressurize the penumatic tank; a submersible pump in the well fills the 1100L tinaco (the pedestal for which can be seen to the left). If the pressure system fails, the system continues to work normally, except on gravity pressure.

For "La Esperanza", a different system was used in which the submersible pump in the cistern also applies the pressure. Apart from requiring only one pump, this provides smoother operation, without the need for a control unit. Here, the submersible pump only has to elevate the water about 7m, compared to about 20m in "El Refugio". But this system is less fail-safe (although the main issue is power outages; submersible pumps appear to be very durable).

Also, although water quality has improved considerably in Mexico over the last two or three decades, tap water is still not considered potable. Even if the water as delivered is of high quality, it will have been compromised by storage in the tinaco. Instead, purified water is available in large bottles, typically with a capacity of 20L. There is no reason why one should not install a water purification system (involving at least ultra-violet light treatment), but this is not commonly done. Bottled water is quite economical, and I have become used to using that.

Outside an urban area, where there is no municipal water supply, it may be provided by a well. This may be private and exclusive (as in "El Refugio") or shared (as in "La Esperanza"). If there is neither municipal water nor a well, it will be necessary to have water delivered by truck (but this situation would not be normal with land privatized for dwellings).

If the water supply is intermittent (e.g. from a shared well or truck), you should build an underground cistern (known as an aljibe) capable of storing a substantial quantity of water. The cistern for "La Esperanza" has a capacity of 12,000L; and with a less accessible supply of water or more occupants, you may want a still greater capacity. With a private well, this will serve as the cistern from which you can refill the tinaco at any time, so an aljibe should not be necessary (unless the well is unreliable). A submersible pump must be installed in the private well or cistern to pump water to the tinaco (refilling of the tinaco will normally be done automatically).

The cistern of "La Esperanza", currently empty after the application of swimming pool paint. The water input valve with stopcock can be seen near the top, and the submersible pump (not yet installed) will be located at the end of the output pipe toward the bottom of the photo. The cistern is located under the entertainment area, and occupies a superficial area of 4m x 2m, with a depth of 1.5m.

5.1.2 Electricity

This is supplied by a government organization called CFE. Voltage is 120V at 60Hz, and the capacity of a standard supply is only 3KW. You can greatly augment this capacity, to give you something closer to what you will be accustomed to in North America or Europe. However, you can and should use much less electricity here in Mexico.

You can also install one or more additional lines, which you will require for 220V two-phase appliances. Note that this is not suitable for appliances from Europe and other areas, which require a single phase of 220/240V; to use these, you will need a transformer.

Billing is every two months, and your power may be cut without warning the day after the due date if you do not pay on time. In most cases, bills are delivered to your house by CFE, and there are several payment options, including machines. Alternatively, bills may be delivered to a shop in your village, and you can pay there (or you can pay by another means if you know your account number).

The cost of electricity is manipulated to make it affordable for the poor. The basic cost per KWh is low with a very low standing charge; thus bills can be very small. However, it can get very expensive with increased consumption. The normal domestic tariff has three tiers:

básico
up to 150 KWh
intermedio
150KWh to 250 KWh
excedente
above 250 KWh

These thresholds apply in my area; in areas where air conditioning is considered necessary, they are higher to take account of this.

If you have a large area of cultivated land, a major expense may be irrigation, which will require significant power for hours at a time. It may therefore be a good idea to install gasoline-powered pumps rather than electric ones (or settle for a smaller piece of land - see Gardens).

There should be a separate meter for each household; the way CFE charges for electricity means that a separate meter should be used wherever permitted. Meters are always installed on federal land where CFE employees are guaranteed access, never on private land. This means that meters will appear on the street (there may also be exposed wiring or circuit breakers - not recommended).

The electricity supply may be unstable, and ideally a whole-house voltage regulator should be installed. You may also consider installing a backup generator, but this provision is less easy to make. Certainly you should use a no-break for critical appliances such as a computer.

Power outlets in Mexican houses are frequently 2-pin (without a ground). Also, there are often very few circuits (perhaps only two or three for the whole house). In electrical installations, there is no reason to do as the Mexicans do; your house should certainly have a properly-grounded power supply with 3-pin outlets, and use a generous number of circuits. But you will probably not find features such as smart meters or GFCI protection.

Generally, it is better to err on the generous side in specifying electrical installations such as power and communications outlets, switches, and lighting. As the wiring is installed in masonry walls, it may be difficult or impossible to add these later without either a serious impact or resorting to makeshift surface wiring. However, the installations of your fontanero should make it possible to replace cables; this will normally require the provision of registros.

Conduits for cabling in "El Refugio", showing one of the registros used to ease (or make feasible) servicing of the wiring. Also shown are some water pipes. As yet there is no cable; this will be installed later.

"La Esperanza" has no internal wall-mounted registros in the house, probably because it is a smaller building on one level (they appear in "El Refugio" only on the upper floor). However, both constructions use a number of external registros.

All gauges of cable used in Mexican house wiring are stranded (as opposed to the solid core cable used NoB for all but the largest gauges). Contrary to certain NoB assertions that it is totally unsuitable for house wiring, stranded cable is essentially§ identical electrically to solid core cable of the same gauge, although rather more expensive. It is used in Mexico as cable is pulled through conduits, and this could cause solid cores to fracture. Stranded cable is mandated for use on aircraft to prevent fracture due to vibration. Different connectors are used for stranded cable, not those commonly used NoB for solid core cable.

5.1.3 Gas

You will almost certainly not have piped gas; in Mexico gas is normally propane, which is delivered by truck. Many people still use 30L gas cylinders, which must be disconnected and reconnected each delivery (the empty cylinder is replaced by a full one). Far better is to install a stationary tank (typically with a capacity of 300L) that can be refilled by a gas tanker. For this, there should be a gas input valve installed in the boundary or house wall, or other easily-accessible position.

The tank will typically be installed on a roof, although a suitable outside area may be a good alternative. If you install the tank where it is exposed to the sun, its capacity is significantly reduced in relation to a shaded location, to allow for expansion.

Typically, gas will be needed only for cooking; in this case you will rarely need to get gas delivered. Other uses for gas include:

water heating
in the absence of a solar water heater, or where this is insufficient
clothes drying
this should be avoided; it is better to use a roof or drying patio
space heating
this may sometimes be necessary in cooler climates

5.1.4 Sewerage

In an urban area, sewerage will normally be municipal; otherwise you must install a septic tank.

North of the border, a septic tank will typically be installed on a large area of land, which can serve as a leach field to break down the output in the soil. In Mexico, the house will typically be built on a plot with no space for a leach field, so the output must be almost clean (gray) water. This requires a 3- or 4-chamber design (the 4th chamber is used to hold gray water that can be used for irrigation). See the bottom-right of the Installations and Finishing Plan of "La Esperanza" (zoom in to see the details).

It appears that most houses in Mexico do not have vented plumbing systems. Here, waste gases are vented to the roof; this helps regulate air pressure for better water flow. The houses of both "El Refugio" and "La Esperanza" have several vent pipes to the roof, and in this area also there is no reason to do as the Mexicans do.

5.1.5 Drainage

Rainwater guttering in Mexico appears to be uncommon; however, as rain can be very intense, guttering might be overwhelmed in a sharp rainstorm. In most cases, the roof is drained by PVC pipes that exit at roof level and drain straight onto the street. In "El Refugio", there is a rainwater drainage well; the flat roofs, terrace and drying patio all drain to this well via embedded and underground pipes. In "La Esperanza", the roof is drained via embedded drainpipes that drain to the path around the house.

Drainage is one of the first things to consider when buying land and designing a new home. As indicated above, there will not normally be underground drainage of rainwater (notwithstanding the special provision of "El Refugio"). Hence, care must be taken with drainage patterns; in particular, all water should normally drain to the front of the property onto the street, and away from any construction.

5.2 Heating and Cooling

The criteria in this section clearly depend on one's location, and hence climate. Mexico has a wide range of climates; I deal only with the two types of climate corresponding to the locations most popular with foreigners: tierra templada (temperate land), and coastal.

The primary means of maintaining a comfortable indoor temperature is to have appropriate construction, especially in the roof. In the first type of climate, thermal mass tends to be most important; in the second, thermal insulation.

Tierra Templada

My location (Zamora/Jacona) and Chapala/Ajijic are typical examples. Both lie at an elevation of about 1600m, at a latitude of around 20°N. The average annual temperature is about 20°C. Overall, it is cool early morning and warm in the afternoon.

In these locations, you will probably be fine without either heating or air conditioning. Most of the year, the average temperature will be close to ideal; however, outside the rainy season there are large daily temperature swings (perhaps 20°C or more). But if your house has good thermal mass, the indoor temperature should be consistent throughout the day. This temperature is likely to be rather higher than the average outside temperature, due to the additional direct heating effect of the strong sun on the masonry.

Winter effectively comprises late December and January. During this period, it tends to be rather cool indoors, but this is best remedied by leaving the windows open during the day, and wearing additional clothing if necessary. Even in winter, it is normally warm (typically 25°C plus) with strong sun in the afternoon, and if you are feeling a bit cold, you can always go outside to get warm!

Conversely in spring, it tends to be rather warm, with high afternoon temperatures; however, the low humidity means that it is comfortable outside in the shade. Indoor temperatures can be moderated by leaving the windows open at night (it is still fairly cool in the mornings). And of course, comfort can be improved by the use of fans (ceiling or freestanding).

If you live at a significantly higher elevation than 1600m and/or significantly further north than 20° (one popular example is San Miguel de Allende), you may want some heating in winter.

Coastal

In these areas, the climate is warm and humid all year, and most comfortable in the winter. Here, the rainy season does not have the cooling effect that it does inland, and summer is usually the warmest season. Due to the humidity, temperature variations throughout the day are less.

Cooling in the form of air conditioning and/or fans would be considered essential, but never heating (except for the most northern parts). Thermal mass here is likely to be less useful, and with air conditioning you will want good insulation to prevent heat from entering a cooled house.

5.2.1 Water Heating

In all parts of Mexico, this should be done primarily by a solar water heater. These come in a variety of sizes, quality levels, and prices. You should probably choose one that has a high capacity (say 300L, even with few occupants), a stainless steel exterior, and which is suitable for use with a pressure system (both hot and cold water should be pressurized). Although not cheap, it will pay for itself within a few years against the cost of using gas; it is also much more environmentally responsible.

Care should be taken when designing the house to accommodate the solar water heater on the roof so that it can be orientated appropriately (for the maximum heating effect, the tubes should be to the south of the tank). For the (probably few) occasions on which the solar water heater is insufficient, an on-demand gas boiler (as they are known in Mexico) should be installed in line with the output from the solar water heater.

The 300L solar water heater of "La Esperanza" on the right; each tube comprises a copper rod inside a vacuum. There is an on-demand gas water heater by the stairs shown in the center of the photo, but we have never had to fire this up.

In the background is the 750L tinaco, with the pressure system behind it underneath steel roofing (this pressurizes hot as well as cold water). There are also frames for the environmentally-friendly drying of clothes.

If you use a black tinaco, you may find that the water is warm enough in the late afternoon for a comfortable shower without any other heating. But this type of solar water heater also means that you will not get any cold water; so to provide cooler water from the cold tap, one should use a white tinaco instead. Or you might try one of each; but you will get much better results from a proper solar water heater.

5.2.2 Space Heating

This should be required only at higher elevations (say well over 1600m), but it seems that there are no good options. I have never seen any central heating in Mexico, even in elevated areas such as Mexico City. Use of additional clothing and blankets is still the norm in winter. Heating comes in the following three forms:

Gas Fire
All those I have seen are freestanding, without any flue provision; as such they are suspect. Even if there is no problem with carbon monoxide, carbon dioxide and condensation will make their use problematic. But if you have a chimney or other vent, and find one you can connect to a flue, it will probably be the best option in an urban area.
Electric Fire
This is clearly highly uneconomic. Even a 1KW fire will considerably augment one's electricity bill, yet do little to heat a sizable house. It will really only be effective in a small house, and then only if one is sitting fairly close to it.
Wood Fire
This must obviously be used with a fireplace and chimney, and probably in a wood-burning stove. It appears to be permitted in rural areas, but clearly not in urban areas. Where firewood is readily available and burning wood is permitted, it has to be the most attractive option.

Reversible ceiling fans may also help with low indoor temperatures. When run in reverse on the lowest setting, the warmer air that is located near the ceiling is pushed down to where people are sitting. This can give an effective temperature increase of 1-2°C.

5.2.3 Cooling

In tierra templada, you will probably find that if your house is substantially built with plenty of thermal mass, you will not feel the need to use ceiling fans that often. This is the case with both "El Refugio" and "La Esperanza" (particularly the former, although this may be partly due to the presence of trees). High ceilings also tend to give a lower temperature where people are sitting.

While the main house of "El Refugio" was being built, I lived in the casita, which has a losa only about 10cm thick. In the afternoon, one could feel the heat coming in through this. Consequently, it could become uncomfortably warm inside from late afternoon, while being cool in the morning. The message is clear: in a climate with large daily temperature swings, you should provide plenty of thermal mass.

In coastal areas, you will probably want air conditioning as well as ceiling fans. Here, insulation is important to prevent the heat that is being lost from re-entering the house.

It is vital to check the performance of ceiling fans. They all tend to have a similar power consumption (typically 75W at maximum), yet vary considerably in efficiency and hence air flow. The worst are virtually useless and simply waste power. The best are 2-3 times more efficient than even a good mid-range fan; however, they are also two or three times the price. Nonetheless, in warm regions where fans will be run constantly at a high setting, it makes sense to invest in the very best quality. A top-end fan will not only be much more efficient at its maximum setting, but is also likely to last much longer.

5.3 Special Topics

5.3.1 Gardens

Most houses in Mexico are built on smallish lots, and have only small areas of garden (if any). Often an area on the roof will be reserved for growing plants (probably only in pots). There are good reasons why private houses do not normally have large areas of garden.

If you would like a larger garden, you should consider carefully what is manageable. The good news is that in most parts of Mexico, the climate will make it possible to grow a wide range of plants. The bad news is that parasites also flourish, and in order to maintain a garden properly, it will be necessary to use insecticides and fungicides. Regular fertilization will also probably be necessary.

It will also be necessary to irrigate during the months of the dry season. The land should therefore have a good supply of water available for irrigation, as you will need plenty of it, especially in spring. If water must be delivered by truck, this is likely to be a considerable expense. In any case, operating irrigation pumps may be expensive. In the rainy season, plants grow vigorously, and it will then be hard to keep the weeds under control.

So a garden in Mexico will require much more attention than in a cooler climate where growth is slower and parasites are fewer. For even a small area, you will probably have to hire a gardener on a casual basis; and you may find said gardener less than reliable or punctual (see the definition of mañana). If you are looking for a large highly-cultivated area (say anywhere near an acre), you are likely to need a full-time (probably live-in) gardener.

Another point about having a large area of land is that it will be more difficult to keep secure; a good boundary wall will be expensive, and surveillance by cameras may be problematic. An ornamental climbing plant that may be helpful with borders is bougainvillea; with its sharp thorns it will be a serious deterrent to any would-be intruder. It is also attractive with bright colors of various hues, and has a very low water requirement.

Note that there are often landslides in Mexico during the rainy season, and land underneath steep hills is at risk of being inundated with mud (and possibly boulders). One example is in Ajijic, where a number of houses are built on steeply-sloping land, with an even steeper slope above. If you don't worry about it and it never happens, then fine; but it is something that one should consider. A bad landslide could be a disaster, causing not only serious damage, but also loss of life.

5.3.2 Wood

Wood is often stated by those NoB to be of poor quality in Mexico. I am not sure to what extent this is true, but one issue that will affect all wood to some degree is changes in humidity. In coastal locations, these should not be too large, and the rest of this section applies only to inland areas.

Away from the coast, there is usually low humidity most of the year, but in the rainy season it is high. As a result, wood dries out and shrinks during the dry season, then expands and warps in the rainy season. Wood takes some time to change with humidity, but in this case the low/high humidity cycles persist for several months.

Many houses in Mexico feature an elegant wood front door, but this is usually in a well-shaded location. It is important that such doors are kept away from the strong sun that will dry out the door in the dry season, and are not exposed to the heavy rain of the rainy season. But even wood doors in well-sheltered locations may suffer minor problems due to changes in humidity. There are also wooden window frames, for which the same considerations apply.

Wood furniture (including kitchen units, tables, cabinets, drawers, shelving, and closets) appears to have few problems, perhaps because these items are made of smaller pieces.

5.3.3 Metal Doors and Windows

These will normally be of either steel or anodized aluminum. The latter is the more elegant option, but steel doors and windows are perhaps more common. These are less cosmetically attractive and will require periodic painting; however, they are likely to be cheaper and may benefit from greater strength. Steel window frames often feature a lattice; while effectively dividing the window into numerous panes, this provides security without the need for external metalwork.

You will probably not find water-tight windows in Mexico of any type (certainly not openable ones). I have never seen factory-sealed units complete with glass, even single-paned, that are simply inserted into place. Instead, windows are assembled (or at least the glass fitted) on-site, and reliability depends very much on the installer. Although the impact of rain entering is less in Mexico with tiled floors and masonry (and a warmer climate) than it would be with carpets and wood, one should bear in mind that the rain can be very intense.

I have also never seen double-paned windows in Mexico, but in most cases, the kinder climate means that the resultant lack of thermal insulation is not a serious issue. However, another benefit of such windows is improved sound isolation; in noisy areas, this might be improved by the use of laminated glass.

Also, in my experience, windows are fitted in the center of the space, rather than being fitted so that the frames are on the same plane as the outside wall. This means that there is a sizable outside ledge. Moreover, I have never seen window sills fitted, and so the outside ledge will collect water with the likelihood of leakage. Some of the leaky windows in "El Refugio" were later dealt with by fitting sloping window sills to drain off the water; this was found to be an effective remedy.

At low latitudes, the sun is brighter, and you are likely to need less window area than you are accustomed to. Although huge windows may look great in photos, they are normally impractical. Apart from the structural issues, they are likely to let in a considerable amount of heat and light, and there may also be privacy issues (especially where the sun can shine straight into the room).

One can deal with excessive light and lack of privacy by the use of mirror glass; however, this is expensive, and only improves somewhat the heat issue (the glass gets hot; the heat is radiated both sides). A lesser option is tinted glass, which is cheaper but has less beneficial effect.

The front of "La Esperanza" faces into the strongest sun and prevailing wind. For this reason, the larger part of the frontage is this covered terrace, which offers excellent sheltering and a more reasonable light level for use with plain glass. And we can leave these windows open during a rainstorm without any risk of rain entering the house, even with a strong wind blowing this way.

The anodized aluminum window and door frames are of a very light bronze color; natural aluminum has a somewhat cold appearance, which would not fit well here.

In contrast, "El Refugio" is open to the sun, and moreover has fairly large window/door areas. This is the west side of the house; all this side and part of the south side have tinted mirror glass. The south side by the stairs and the east side have plain tinted glass.

In general, I recommend that where there are significant areas of openable window, that they be well sheltered to avoid rain entering. This may be achieved by incorporating covered terraces and balconies with a sufficient size of roof. These may also be useful in reducing the light and heat entering the windows. However, paper wasps may see covered terraces and balconies as nice places to build a home, especially if they get plenty of sun.

5.3.4 Appliances

In this section, I list some appliances normally found in North American and European houses, but which are rarely seen in Mexican houses, with good reason. The cost of higher consumptions of electricity is one such reason, but otherwise one can manage happily with less.

Chest Freezer
This proved to be a complete waste of space:
  • Before moving to Mexico, a chest freezer was useful for storing large quantities of frozen food purchased at low cost in bulk. It could be kept in a garage or other area that remained cool, thus making it economical to run.
  • In Mexico, I have not seen any bulk sellers of frozen food. Moreover, the higher ambient temperature together with the high cost of upper-tier electricity mean that it would not make economic sense.
Clothes Dryer
Those I have seen in Mexico commonly use gas rather than electricity, which should reduce the running cost. "El Refugio" has a gas supply for a dryer, and I almost bought one, but thankfully never did. Even in the rainy season, it is never a problem getting clothes dried, and burning fossil fuels would be reprehensible. In designing a house, one should provide an area of flat roof with easy access from the laundry room for hanging clothes, or alternatively a drying patio at floor level where it will receive plenty of sun.
Dishwasher
This is more marginal, but even though I now have a 2-person rather than a 1-person household, my dishwasher is essentially redundant. It now seems easier to wash dishes in the sink (perhaps helped by the fact that water always emerges at a comfortable temperature, and dishes dry quickly). The high cost of electricity is a deterrent to its use, and it is not easy to find dishwasher consumables.
Vacuum Cleaner
Again, this may not be entirely useless. However, without carpets its usefulness is limited to curtains and possibly soft furniture. It is much easier to clean tiled floors with the traditional broom and mop.

5.3.5 One Floor or Two?

This will be the usual choice; few people will build a house with more than two complete floors. A third level with reduced area (for example, a room housing the tinaco) is quite common; but this will typically be of lightweight construction, and have a nonstructural roof. Basements are not usual in Mexico.

While personal preference will often be the biggest factor, the nature of the lot and economics are also considerations. Lots in urban areas are typically small with a high cost per unit area, and in this case it may be necessary to build on more than one level to provide sufficient space. However, outside city centers it should be possible to buy a good-sized lot at a modest price, which will be no deterrent to building on one level. In this case, the construction cost per unit floor space is the main consideration.

A multi-story construction will have only one foundation and one roof for a larger floor area. However, the cost of a proper structural roof will be similar to that of an intermediate floor, so the main difference is less cost in the foundation. On this basis, a two-story house works out cheaper per unit area.

Against this, a two-story house has more structural issues to consider than a one-story one, and may require a more expensive foundation. The wall density must be greater on a lower floor (meaning thicker walls, or more of them); otherwise this must be compensated for by other means (for example, appropriate use of structural columns). Generally one can get away with cheaper construction with a one-story house than a multiple-story one, especially with a more elaborate design (not a simple rectangle with high wall density). Another factor is that labor costs are higher for working on an upper floor (the union prices are 10% higher).

Glosario

Este glosario contiene solamente definiciones que aplican a este blog de construcción. Muchas palabras tienen otros significados en otros contextos.

Alambre Hilo para amarrar alambrón y varilla. Alambre quemado es de acero más durable.
Alambrón De acero un poco rígido, normalmente de diámetro 1/4 pulgada, para hacer estribos.
Anillo = estribo.
Aparente Acabado que se ve como material natural, frecuentemente hecho de concreto tinto. También se lo usa para material estructural acabado bien.
Aplanar Cubrir los muros con material de concreto durable antes de poner textura y/o pintura.
Aplanado Material que se usa para aplanar.
Bailarina = a compactador.
Boquilla Detalles de muros - es decir todas las partes que no son partes de las área principales. Incluye alrededor de puertas y ventanas, y las partes arribas de muros. Se hacen cálculos separados de los costos de estas partes.
Bóveda Un tipo de techo que comprende arcos de tabique entre viguetas - se la encuentra más frecuemente en el estado de Jalisco.
Cadena Un trabe que su usa para conectar elementos estructurales, por ejemplo en la cimentación.
Castillo Elemento vertical de concreto refuerzo que se usa con dalas para confinar secciones de muros para darlos resistencia a sismos.
Cimbrado Colocar tablas de madera para formar el concreto.
Cintarilla Tipo angoso de baldosa.
Columna Similar que castillo, con sección circular o más robusto donde se ocupa más refuerzo.
Compactador Máquina neumática para compactar el filtro y la arena.
Contratrabe Un tipo de trabe que se usa en la basa de una cimentación de concreto refuerzo.
Dala Elemento horizontal de concreto refuerzo que se usa con castillos para confinar secciones de muros para darlos resistencia a sismos.
Dala de cerramiento La dala ubicada a un nivel de acerca de 2.1m, usada para soportar el muro encima de las puertas y las ventanas.
Dala de coronación La dala a la parte arriba de un muro.
Dala de desplante La dala que se usa en la parte arriba de la cimentación; normalmente está un poco abajo del nivel del suelo.
Estribo Hecho de alambrón; se lo usa para formar castillos y dalas.
Filtro Un tipo de grava roja y absorbente para llenar espacios.
Firme Una capa de concreto que forma la base del piso antes de colocación de piso.
Granito En albañilería significa piezas chicas de piedra como mármol.
Hormigón Material que se usar para hacer un tipo de concreto ligero.
Losa Bloque de concreto refuerzo que se usa para techos y pisos; para techos planos, se la cola como una pieza.
Malla Hecho de acero, que se usa para reforzar losa, y también en nuestro caso la barda.
Mañana This is the usual reply you get when you ask your gardener (or other worker) when he will be back to complete the work. This would normally be translated as 'tomorrow', or alternatively as 'morning'. However, the Oxford Spanish Dictionary lists a third figurative meaning: 'in the future', and this is the interpretation you should make if you owe him money for work done. Otherwise, a more generalized translation applies: 'not today'.
Obra negra Trabajo nada más estructural, lo cual ocupará un acabado para dar una buena apariencia.
Plantilla Una base de concreto pobre encima de la cual sientan las zapatas.
Pulido Espejo Cemento fino para un acabado pulido.
Revuelto Material que se usa para llenar espacios; normalmente como rocas y arena (no como filtro).
Trabe Una viga de concreto refuerzo, como una dala, pero indica otro usa que confinar secciones de muros (por ejemplo contratrabe en la base de la cimentación, o el trabe encima del portón).
Trompa Máquina para bombar concreto premezclado a su sitio.
Zapata El refuerzo a la pie de la cimentación.
Zapata Corrida Zapata continua que se usa a la pie de una cimentación de concreto refuerzo; este tipo de cimentación es flexible y amarrada, no como una cimentación tradicional de roca que pueda abrir en un sismo.