“Repairing and Preserving Your Adobe Home” by Roy E. Spears
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Chapter 2
The Number one Enemy of Adobe
(If your home needs adobe repair work, please click here.)
Water and adobe don’t mix well. A brief interaction might cause little harm, but any long-term contact will inevitably damage the adobe. Moisture and water damage are among the most destructive issues that can affect houses, even those built with conventional materials.
Below are several paragraphs from the September 1996 issue of “Paint and Coatings Industry.” I believe these excerpts provide an excellent insight into the problems of water intrusion in 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 with a modern Portland cement based stucco may be one of the worst things you can do, for several reasons.
The ability of adobe to “breathe” is one of the most critical factors for ensuring its longevity. To “breathe” means that the adobe can release water vapor when it becomes damp. Adobe can usually adequately breathe only if it is exposed to the elements, i.e., not covered with stucco, paint, siding, or similar materials. If you can see each individual adobe brick and the mortar joints in your walls in their natural state, then your adobe structure can breathe. However, if stucco, siding, plaster, or paint covers your adobe, its ability to breathe is restricted.
When moisture is introduced into adobe, it begins to lose its strength; the wetter the adobe gets, the weaker it becomes. Properly made adobe is completely dry, hard, and the compressive strength of each individual block is relatively high, allowing it to bear a significant amount of weight. However, adding moisture makes the adobe weaker. Depending on how wet it becomes, the dry, hard earth that forms the adobe is in danger of reverting back to its original state: mud. Mud is not strong and cannot bear any weight. While mud might be great for rejuvenating one’s tired and wrinkled face, no one would seriously consider 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 usually fare well. If the adobe home has wide overhangs covering most or all of the house, or is surrounded by porches, then rain is less of a threat, especially if the home is also protected by a relatively high foundation system. This foundation system must be paired with proper drainage to direct rainfall away from the house rather than towards it. If the adobes do get wet, they soon dry out. This is not to imply that stuccoing, painting, or attaching siding to your adobe home is always harmful or that you need to remove these to prevent your house from falling apart. Many factors play important roles in the preservation of adobe, and often one factor can offset the benefit of another.
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 and collect 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 “breathability” severely restricted. In the case of the home mentioned in the previous checklist, these covered adobes will absorb water from both rainfall and overwatering of plants. Instead of being able to dry out by releasing trapped moisture, the stucco blocks the necessary circulation and traps the moisture inside. The sun cannot reach these covered adobes, causing them to remain moist far longer than usual.
The stucco also hides the deterioration caused by water infiltration. Without stucco covering the adobe, you would notice any signs of deterioration as you walked around your home and could quickly take remedial action by redirecting water away from the walls or repairing the damage. However, with adobes covered in stucco, this visual opportunity doesn’t exist. The only way you can usually tell 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 to inspect a problem with a non-stabilized mud adobe home just east of the University of Arizona. The home was not stuccoed, so I could see each adobe that made up the structure of this beautiful, older house. The customer directed me to a specific problem area where portions of the adobes were literally breaking off from a rectangular section about 2’ x 3’ in size. It was unusual for just this one area to be failing, and we subsequently discovered that this area was directly opposite the shower on the other side of the wall.
The shower itself was tiled, and the problem became obvious: the grout and caulk joints were failing and needed to be replaced to stop the water from seeping through and behind them. Another possible cause of the deterioration could have been a leak in the piping that supplied water to the shower. Because the exterior of the home was not covered by cement-based stucco, which would have trapped the moisture and hidden the damage, the issue was quickly noticed, and the source of the damage could 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 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.