Chapter Two

“Repairing and Preserving Your Adobe Home”

by Roy E. Spears

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Chapter 2

The number one enemy of Adobe

Water and adobe don’t fare well together; they may occasionally meet and suffer little from their brief interaction, but any long term relationship between the two will only mean that the adobe will lose in the end. Moisture and water damage to houses, even conventionally built ones, are one of the most damaging occurrences that can happen to our homes.

Below are several paragraphs from a magazine titled “Paint and Coatings Industry” from the September 1996 issue, giving what I believe to be an excellent window into the problems of water intrusion into our homes and other structures:

“Aside from abrasion, virtually all degradation involves water. Mineral construction materials can, by virtue of their pore structures, absorb water through their capillaries. Water enters not only through exterior facades, but also by the humidity within buildings, by groundwater and by penetration through cracks, seams and joints…

Water itself causes freeze/thaw damage…water in construction materials supports biological growth that degrades mineral-based materials.

“History has shown that for every 100 buildings, 24 are damaged in the first year, 15 in the second, seven in the third, six in the fourth and three in the fifth. This means that 55% of all buildings are damaged within five years. The annual cost of this damage can run into the billion-dollar range.”

Keeping water away from your adobes is the most important aspect of protecting your home. Unfortunately, some of the methods for doing this have actually caused more harm than good. For instance, stuccoing your adobe home may be one of the worst things you can do, for several reasons. (Please note that the following information is referring to non-stabilized, sun-dried adobe, and does not necessarily refer to burnt adobe.)

The ability for adobe to “breathe” is one of the most critical factors to insure its longevity. To be able to “breathe” simply means that the adobe has the ability to release water vapor once the adobe itself becomes damp. Usually, adobe can only adequately breathe if it is open to the elements, i.e., it is not stuccoed, or painted, or covered with siding, etc. If you can actually see each individual adobe brick in your walls in its natural state, including the joints, then you have an adobe structure that is able to “breathe.” If stucco, siding, plaster or paint hides your adobe, then the ability of it to breathe is restricted.

When moisture is introduced into the adobe, it begins to lose its strength; the wetter the adobe gets, the weaker it becomes. Naturally, when adobe is totally dry it means that it is hard, and the compressive strength of each individual block is relatively high, resulting in each dry adobe able to bear quite a bit of weight. Add moisture to this same adobe and naturally it becomes weaker, for the dry, hard earth that the adobe is made up of is now, depending on just how wet it becomes, in danger of reverting back to its original makeup: mud. We know that mud is simply not that strong, offering no strength to allow any weight to bear on it. Mud may be a great thing for rejuvenating one’s tired and wrinkled face, but no one would ever seriously think of living in a liquid mud house.

Small amounts of moisture in an adobe brick is not particularly detrimental if that moisture is allowed to quickly evaporate from that adobe. Adobe homes are predominantly constructed in desert environments where rainfall is seldom and there are usually long dry spells between these rainfalls. Certainly living and having been raised in Tucson, I am aware of the monsoon season where we get much of our annual rainfall over the space of a couple of months. Often times this amount of rainfall falling at one stroke can be quite voluminous, but usually the desert sun quickly comes back out and everything goes back to becoming bone dry.

Adobe structures in this type of environment fare well—usually. If the adobe home has wide overhangs covering all or most of the house or is surrounded by porches, then rain is not such a threat if the home is also protected by a relatively high foundation system. This foundation system must be coupled with proper drainage of that rainfall coursing away from the house instead of towards it. If the adobes happen to get wet, they soon dry out.This is not to infer that stuccoing, painting or attaching siding to your adobe home is harmful and that you need to remove it to prevent your house from falling apart. There are many factors that play important roles in the preservation of adobe, and often time’s one factor will negate the benefit of the other.

The following list will help you to identify problem areas associated with your adobe home. Does your home have:

·Cracking Portland cement based stucco?

·Small, shallow or non-existent porches?

·A foundation system which places the adobes on or close to grade?

·Landscaping that directs water towards the house?

·Plants less than six feet from the house?

·Planter boxes attached to the home and filled with water-hungry plants?

·Rain scuppers or drains that dump water on the ground directly below them?

·Irrigation lines running near the perimeter of the home?

A home with any of the above problems will need to have those problems corrected to insure that water will not cause damage.

Adobes covered by cement based stucco have their “breatheability” severely restricted, and in the case of the home in the preceding check-list, these covered adobes will be sucking up water, both from rainfall and over watering of plants. Instead of being able to dry out by releasing their trapped moisture, the stucco cuts off the critically needed circulation and traps this moisture in. The sun can never reach these covered adobes so they will stay moist far longer than normal.

The stucco also hides the deterioration caused by water infiltration. If there were no stucco covering the adobe, you would notice any sign of deterioration happening as you walked around your home. You could quickly take remedial action, by redirecting water away from the walls and/or repairing the damage. With those adobes covered in stucco no such visual opportunity exists; the only way you can usually tell that the adobes are having problems is when the stucco shows a telltale bulge, signifying a separation is occurring between the stucco and the adobe.

I was called out to look at a problem on a non-stabilized mud adobe home just east of the University of Arizona. The home itself was not stuccoed, which meant that I could see each adobe that made up the structure of this beautiful, older home. The customer directed me to a specific problem area which showed portions of the adobes literally breaking off from an area that was rectangular in shape, about 2’ x 3’. This was unusual for just this one specific area to be failing, and it was subsequently discovered that this area was directly opposite from the shower that was on the other side of the wall. The shower itself was tiled, and the problem became obvious: the grout and caulk joints were failing, needing to be replaced to stop the water from seeping through and behind them. Another cause of the deterioration could also have been a leak in the piping that supplied water to the shower itself. Because the home was not covered by a coat of cement based stucco that would have trapped the moisture in and also hidden the damage, the damage was quickly noticed and the problem causing the damage could then be easily identified.

On the other hand, a good case can be made that the stucco protects the adobe by giving to them a “skin” of protection that prevents water from hitting them directly, thus preventing erosion. This is an excellent example of one benefit defeating the other. The stucco may give the adobes added protection, but by removing the ability for the adobes to release trapped moisture you are killing them in another. I have seen many instances where stucco covering the adobe has hidden pronounced deterioration, with the adobes literally melting away unseen underneath this protected skin.

In all fairness, I have seen adobe houses that were truly protected by their coats of stucco (see chapter 10, section B). Houses that are built so that the adobes are on a fairly high foundation system that keeps them off of grade and have excellent drainage with generous porches and overhangs, consistent maintenance that repairs cracks in a timely fashion – these are the types of homes where stucco truly makes sense and results in giving the adobes a far longer life span.

If an adobe house will be able to remain dry at all times with no water being able to come in contact with them, a good stucco coat will be a protective benefit. If water cannot be kept from the adobes due to the previously addressed problems, stuccoing an adobe structure will only invite failure of the material.

Roy Spears