“Repairing and Preserving Your Adobe Home” by Roy E. Spears

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Chapter 1

(If your adobe home needs adobe repair work, please click here.)

The different kinds of adobe

In the introduction to this manual I briefly touched upon the different kinds of adobe block that have been used to construct homes; in this chapter I will go into more detail describing the various kinds of adobe.

Burnt (or fired) Adobe

Burnt adobe are earth/clay bricks that are mined from areas in Mexico, and this mixture is placed into wooden forms, allowed to dry, then placed in kilns where they are fired for a certain length of time. Among burnt adobe are two main types: Sasabe and Querobabi.

Sasabe adobe are made and transported out of Sasabe, Mexico, a small border town in Arizona. These are the characteristic orange adobes that one sees on so many adobe homes in Tucson. The other type, Querobabi, are made and transported out of Querobabi, Mexico, and are of a distinct reddish hue and represent a far less percentage of adobe homes built in Tucson. These adobes are no longer made or available, as explained more fully below. My experience in dealing with these two types of adobe is that the Querobabi is a superior block than its counterpart. The Querobabi adobe is interesting in that it appears, when working with it, to be more fragile. It weighs less than the Sasabe and almost seems as if it has a hollow ring to it when the block itself is tapped. Yet this Querobabi adobe is amazingly durable and seems to deteriorate at a far slower rate than the Sasabe. It is rare that my company is called in to repair deteriorated Querobabi houses, and when we do, the number of bricks that we need to repair is usually of a far less number than when we are called to repair a Sasabe home.

In December of the year 2000, I was called to give an estimate on repairing a wall in Green Valley. An elderly woman had run her car into the corner of this wall, knocking it down. This wall was made of 8″ x 4″ x 16″ regular cement blocks, with Querobabi adobes used as a decorative screen insert in the center of the wall. The cement blocks were stuccoed, leaving the Querobabi adobes natural.

Many of these adobes were broken and would have to be replaced with new Querobabi adobes, but you cannot buy Querobabi adobes anymore because they are no longer shipped to the U.S. from Mexico. Why? I’m not sure, but rumor has it that the family that owns this particular adobe making facility in Querobabi, Mexico were having some type of internal, family problems and were interested in having someone buy out their operation.

I explained to the customer that I would have to replace the broken Querobabi’s with Sasabe adobes, and because of the color difference between the two adobes, she would have to expect a finished product that would have different color variations instead of one even color. She didn’t seem to like this explanation, and asked me what I would charge to knock the entire wall down and rebuild another on, because she didn’t really like the look of the old one anyway. I figured out what it would cost, and she told me to take to her insurance agent as this was going to be an insurance claim anyway.

When I talked to her agent and explained the problem with not being able to replace the Querobabi adobes, the agent agreed with me that I would have to knock the entire wall down and replace it with a new one. With that said, I scheduled the demolition of the wall to begin.

The interesting part of this story is that this wall was at least thirty years old, and the Querobabi adobes, except for the ones broken by the lady driving her car into them, were virtually perfect. There was virtually no deterioration of any kind on any of these adobes, and this is an enduring testimony to the high quality of these particular adobes. Because of this, I carefully removed these adobes from the wall before taking a sledgehammer to the rest of the cement blocks, storing the Querobabi’s at my house and also at my material yard. Though I will not go so far as to say that Querobabi adobes are priceless, I know that their value is far above what you would normally pay for a Sasabe adobe, not only because you cannot buy Querobabi’s anymore, but because the Sasabe’s are very inferior to them.

I have seen that the quality of the Sasabe’s is not nearly what they used to be. Often times you will see that the Sasabe’s are melting away right on the pallets that they are sitting on, before they even have a chance to be mortared into a wall. The only explanation that I can give is this: just like “old growth” lumber was the best that houses could be built out of, so are “old” Sasabe adobes. As these “old growth” forests were depleted, the newer trees were harvested and used in the housing industry. Builders know that this new lumber pales in comparison to the old timbers, and so it is with adobes. I think that the best soil used to make the old adobes have been exhausted, and the newer adobes are made from inferior clays. Thus, they no longer have the ability to weather that the old ones had, and it takes only a small amount of rain to begin to melt these new kids on the block.

I would not use new Sasabe adobe to build anything, for I have witnessed first hand the problems associated with them. I occasionally get asked what is the difference between these two types of blocks, why one is better than the other, and I have come to the conclusion that it has to be because of the difference in the soils between the two areas. Also, there is the obvious color difference between the two.

San Luis Adobe

Another type of brick from Mexico that is of the fired, but of a far less common variety, is the San Luis Adobe. This is by far the most beautiful of all the adobe blocks made in Mexico, being multicolored with yellows, blacks, oranges, browns and reds throughout the brick. There are also floor tiles made with San Luis, and I used these floor tiles when I put a wood stove in my home and used the San Luis as my base that the wood stove rests upon…quite pretty.

The San Luis is rare in Tucson, and not many houses have been built with them, which I think is a pity. They seem to be a durable adobe, as I have not had to repair too many of them.

Stabilized Adobes

What is a “stabilized adobe”? The term can be confusing and may lead some readers to erroneous conclusions. Webster’s defines the word “stabilize” as “to keep from changing…to make stable, or firm.” When applied to adobe, one gets the impression that stabilized adobe is one that doesn’t change or remains firm in the sense that deterioration will not occur. In simple terms, stabilized adobe shouldn’t revert to the state it was birthed from: mud. Unfortunately, for word purists, this is not the case. Stabilized adobe, though more impervious to water deterioration, is still comprised mostly of clay and dirt, and the small percentage of the stabilizing agent added to the adobe is not enough to completely stop the damaging erosion of water penetrating the block. There is an exception to this, though, and will be explained below.

There are two main types of stabilized adobes currently available in Tucson: cement stabilized and asphalt emulsion stabilized. When cement is used as a stabilizer, we are talking about Portland cement. The percentage of Portland cement added to the earth/clay mixture can be between 2-9%. The addition of this Portland cement causes the block to change color, and most people, when they think of adobe, think of a block that looks like—dirt. The cement, depending on the percentage added, turns the brick, the earth/clay mixture, towards the light side, almost a straw color. The more cement that is added, the lighter in color the block becomes.

The issue of color now comes into consideration, for the look of the different types of stabilized blocks may, and sometimes does, cause concern for some adobe lovers. Some people do not like the look of cement stabilized adobes, thinking the color looks artificial and going in a direction away from the natural appearance of what adobe is supposed to look like. Others, including myself, prefer the light color of cement stabilized to the darker color of the asphalt stabilized.

Asphalt Emulsion Stabilized

Asphalt stabilized, as the term implies, uses asphalt emulsion as the stabilizing agent. Asphalt is a black oil additive that changes the look of the earth/clay mixture once it is introduced into the mixture, turning it a chocolate brown color that lightens up as the block is exposed to the elements. I don’t mind the look of this block either; I think that the color is not so dark as to make the brick look unappealing. Then again, I prefer the lighter look of the cement stabilized, just as I prefer the lighter look of natural oak as opposed to the darker look of honey oak.

When I put a wood floor down in my house, I was thinking about putting down a mesquite floor. I appreciated the extreme hardness and durability of the mesquite as opposed to other hardwoods, but I did not want that dark of a wood covering so much square feet of my home and casting a dark pall over my home. I chose ash instead, which is a light, blond wood and I have never regretted my decision. I simply prefer the lighter look, while others may prefer a darker appearance.

Which block is better, cement stabilized or asphalt emulsion stabilized? This is not simple to answer, for there are many variables that come into play that would make one system better than the other; if one of these factors would be changed, the other system would be in a position to edge out the other.

For instance, if the soil that is used in making the block in the first place changes, the integrity of the entire block will be compromised. I was called to do some serious restoration work on a cement stabilized mud adobe house less than three years ago. The house was new, having been under construction for only six months or so, yet many of these new adobes began disintegrating soon after being laid and after only having been exposed to several monsoon rains.

The problem with this large batch of adobes was that the earth/clay mixture that was used in actually making the adobes was not thoroughly mixed together, and large lumps of clay were left unmixed with the earth. When moisture reached these adobes, the unmixed portions of clay absorbed water, this clay then expanded at a rate much faster than the surrounding earth, and the adobes literally “blew up.” To say the least, this home, even after we did thousands of dollars of remedial work, still experienced problems. We learned one important lesson from this project: always start your project with an excellent set of adobes, or you will pay dearly for inferior adobes many times over.

Another situation that I have been called to address concerned an asphalt stabilized home that again, was relatively new. This particular home was less than five years old, and already, within these five years, had two different contractors trying to solve the problems. I was the third. This house had a thick (in some places 4″ thick) asphalt stabilized plaster coat troweled on over the asphalt stabilized adobes. The look of the home after this earth plaster coat was beautiful…very Santa Fe looking with rounded corners. The problem was that this earth plaster coat wasn’t adhering properly to the adobe, even though the earth plaster was made out of the same material as the adobe and purchased from the same adobe yard. I could easily pull off the plaster coat from the adobes in many areas of the home, particularly around each of the windows that were not protected by a porch. Part of the problem was that the rain was leaching through the failing caulk joints between the wooden window frame and the plaster coat that butted up against the wooden window frames. As the water worked its way down the walls, it somehow began separating the plaster coat from the adobes, and was coming off in many areas.

Since I was the third contractor called out to this project, I felt that I needed to do something different than what the other two contractors did and not simply tear off the failing plaster coat and put on a new one. Since this remedy was already tried twice before and failed, I felt another approach was mandated. My crew and I ended up ripping off the plaster that was failing, attaching galvanized metal stucco mesh on these areas, applying two coats of stucco, then covering the stucco with the earth plaster mix. Even after doing this I still wasn’t convinced that this would solve the problem, for I felt that the earth plaster was not going to properly bond to the stucco and the next rain would begin to wash it away. So, we applied one of our specialty water repellents to these walls, and then the customer, on my recommendation, several months later applied rollable synthetic stucco to the entire house and their surrounding walls.

The unfortunate part of this was that the homeowners eventually sold the house and moved out of state, back to California where they were originally from. After dealing with three different contractors in less than five years, making an insurance claim to their insurance company for the necessary repair work, fighting with the manufacturer of both the adobe and the plaster mix, fighting with the general contractor who originally built the house, threatening law suits against both the general contractor and the adobe manufacturer, they had enough and moved. It was quite a sad ending to what they both had hoped would be their dream home.Part of the problem with this home was that the manufacturer of the adobe claimed that the general contractor who built the home did not follow their recommended mixing rates for the earth plaster coat. The manufacturer said that the general contractor skimped on the amount of asphalt emulsion that should have been mixed with the dirt to form the plaster coat itself and that this was why the plaster coat failed.

The General Contractor (G.C.) said that the manufacturer was crazy for even suggesting this and that the real problem was the materials sold to the G.C. were inferior in the first place, that the manufacturer sold the G.C. a batch of improperly mixed adobes and plaster coat and this was what the problem was. To say the least, the arguments went round and round with nobody admitting anything, and the only real action that was taken was on the part of the home owners when they put a “for sale” sign out on their property.

I saw things from a different perspective. My company was on this project off and on for a total of six months. One day, while working on the inside of the house tearing off some loose plaster and replacing it, a summer monsoon came. The storm that hit this house was so intense that it dumped at least an inch of driving, pounding rain against that house in less than ten minutes, and this was one clue, to me at least, why the house was having so many problems.

The house was built in the wrong place for the style of home that it was, for the geographical location of the house put itself in an exposed area that took an usual amount of battering from the weather. It was a Santa Fe style home, which means that it had no overhangs to speak of, and the only protected areas the home had were underneath the porches. Building a Santa Fe style dirt house on top of an unprotected high hill in the middle of nowhere with gale forces winds and pounding monsoons battering it to pieces was simply not a good choice. After that storm I felt that the best structure for that particular location would have been a lighthouse.

Another problem that I continually encountered on this home was the failing caulk joints previously alluded to. The original caulk that was applied to the gap where the wooden window frames met the earth plaster seemed to be of good quality, but each time a downpour slammed against the home, the unsealed mud plaster began to “dust” off. The results of the rainwater washing away some of the adobe itself could easily be seen by the little piles of the earth plaster aggregate all along the perimeter of the home. As this mud plaster underneath the caulk slowly began to dissolve, the caulk began pulling away and soon was failing in many areas, allowing water to pour into the crevice made by the failing caulk.

I attempted to slow down this “dusting” problem by sealing the edge of the mud plaster with a special formulation of my adobe water repellent before applying the most expensive caulk that we could purchase at Home Depot. This was the GE silicone caulk that was selling for approximately $5.00 a tube. My philosophy in this case was that I needed to completely stop this “dusting” problem so that the caulk joints would no longer fail. Did this permanently solve this particular problem? I honestly do not know, as I have not been back at the house in several years to investigate whether or not my solution proved to be a permanent one.

Being a contractor for two decades has shown and taught me many lessons, with one of the most important ones being in the “people” realm. Human error is responsible for many of the problems that we run into in construction, and in the case of adobe construction and adobe making it is just as valid. I truly believe that at least some of the time the problems that adobe manufacturers face as far as quality control is concerned is directly related to what the adobe manufacturers workers may or may not be doing.

I know that my employees have good days and bad days, days when production and craftsmanship is way up and days when production and craftsmanship is not so good. If an adobe manufacturer is relying on his employees to consistently and accurately measure out the correct amount of whatever stabilizer they are using to “weather proof” their blocks, then one can see how a worker having a particularly bad day could very well make some mistakes that could seriously compromise the quality of that particular batch—or run—of adobes.

Then there is always the ever-present reality of equipment malfunctions, weather problems, too much heat or not enough heat. The remote possibility of a hard freeze occurring that could easily ruin an entire day’s production of adobe making is also a concern. Freshly made adobes, still wet from being poured into molds, sitting overnight to begin the curing process can be ruined if they freeze overnight.

Previously I mentioned one type of cement stabilized adobe that seems to truly be impervious to water damage, as proved in a very convincing demonstration by the manufacturer of this one particular block. One of these adobes was completely submerged in a tank of water and allowed to sit like this for several days, whereupon the submerged block was taken out and examined. Amazingly, the adobe brick was still in one piece, and seemed none the worse for having been soaking for several days! No pile of mud was evident on the bottom of the water tank, nor was there any sign of the adobe breaking into chunks or any of the top layers sloughing off.

But the drawback to this type of block is the color; the high concentration of Portland cement put into the block to make it water proof appears to give it a distinct yellowish white, similar looking to your typical slump block. Probably not the best choice for someone who is searching for that true “Southwest” look, but perhaps an excellent choice for those who want an “adobe” home without the accompanying hassles and maintenance that so often goes with adobe home ownership.

Cement Stabilized Compressed Adobes

Cement stabilized compressed adobes are made with Portland cement, very little water in the earth/clay mixture, and then this mixture fed into a machine that compresses the adobe and then spits them out of a chute one at a time. When done correctly, these adobes are quite strong, dense, very heavy and long lasting. Many adobe homes are built (at least in New Mexico) with this machine on site. As the freshly compacted and compressed adobes come out of the machine, they are slid onto a set of runners and rollers to make their way to where the adoberos are laying up the walls.