The problems with asphalt stabilized mud adobe.

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© 2024 by Roy Spears. All rights reserved.

In my decades-long career as an adobe repair and preservation specialist, few challenges compare to the enduring issues with asphalt-stabilized mud adobe. One notable project from 1995 stands out: a Santa Fe styled house on Bluebonnet in Tucson, constructed with these adobes and covered with a thick coat of earth plaster. The manufacturer, long out of business, touted the adobes and earth plaster as durable, yet the reality was starkly different. Over time, the earth plaster cracked, allowing moisture to infiltrate and undermine both the plaster and the adobe beneath.

This home, an insurance job through Farmers Insurance, required extensive restoration due to water damage. Despite investing over $35,000 in repairs (equivalent to approximately $102,160 in 2024), the problems persisted. Farmers eventually halted further repairs, leaving the project incomplete. This experience underscored the critical importance of understanding material durability in adobe construction, a lesson I’ve carried throughout my career.

By this time, I had about ten years of hands-on experience in adobe restoration. Most of my work had involved burnt adobe, not the newer asphalt-stabilized mud adobe from this manufacturer. Working with earth plaster was a new experience for me, though I was familiar with cement-based stuccos commonly applied over adobe. These cementitious coatings often failed, requiring frequent maintenance and upkeep, issues I regularly handled early in my career.

The primary issue with the Bluebonnet house was moisture penetration through cracks and voids in the thick earth plaster coating. A significant disadvantage of earth plaster is its tendency to crack, regardless of how carefully the materials are mixed. These cracks, ranging from hairline to larger ones, allow rainwater to penetrate, soaking both the plaster and the adobe underneath. This moisture infiltration can lead to serious damage and potential disaster.

The house faced significant issues due to extensive cracking in the earth plaster, which allowed moisture to percolate through. Consequently, the earth plaster delaminated from the adobe it was meant to protect, leading to the deterioration of both the plaster and the adobe.

As I’ve mentioned throughout this website, water is the number one enemy of adobe. Prolonged contact with water turns earth into mud, weakens it, and can lead to the collapse of the structure if neglected, potentially ruining the building.

And here is where my “parting of the ways” began with John Smith (not his real name), the man who made the adobes and earth plaster on the Bluebonnet house.

Since the construction of the home used Smith’s adobe and earth plaster, it made sense to use his materials for repairs. Using the same materials ensured compatibility and proper adhesion between the old and new. Therefore, I visited Smith’s adobe manufacturing plant in Tucson to purchase the needed materials.

I was impressed with his operation, particularly his office/showroom. He constructed it using his characteristic chocolate-colored asphalt-stabilized mud adobe and incorporated huge beams into the roof structure, creating a homey, earthy, and masculine style.

This marked my first visit to this location and my initial meeting with Smith himself. At the time, I was in my mid-thirties, dressed in typical contractor attire: rugged and suited for outdoor work. I likely entered his establishment wearing my ever-present wide-brimmed sun hat, a long-sleeved white shirt, and well-worn work pants. Admittedly, my attire may not have been ideal for making a strong first impression on someone of Smith’s reputation and caliber. His office/showroom appeared tailored not for contractors like myself, but for affluent clients who came to be impressed by Smith’s building materials and house plans for their home constructions.

He was much older than me, likely in his fifties or sixties. I walked in, looking to find out what I needed to purchase for the Bluebonnet project. He immediately sized me up as someone he wouldn’t spend much time with. His reception was icy, far from a warm and enthusiastic welcome. I felt uneasy about the unfriendly vibe Smith projected during our first meeting.

He was dressed in business casual attire: nice, clean, and crisp, a stark contrast to my well-worn, probably dirty, and wrinkled work clothes. I introduced myself, but Smith’s icy demeanor never softened. He had a superior air about him, and I felt out of my comfort zone in that showroom. I was on his turf, and he had the distinct home court advantage.

At this point in my career, I had about ten years of experience in adobe home restoration (now nearly 40 years). I knew how water adversely affected adobe and how overzealous homeowners, desiring lush greenery like Nebuchadnezzar’s Babylonian gardens, often caused damage. Such landscaping required frequent watering, which was, and still is, detrimental to adobe homes.

Mixing and applying a mud plaster over an existing one, repeated every few years. (Library of Congress)

My opinions about adobe were shaped by my experiences as a hands-on contractor who made a living repairing and preserving them, a perspective quite different from an adobe manufacturer or homebuilder. This difference in perspectives is foundational in understanding the tensions between those who repair adobe and those who build, manufacture, and promote adobe as a building material.

A builder of adobe homes or an adobe manufacturer approaches adobe construction differently from an adobe preservationist. This distinction is crucial for understanding the conflicts among these parties. Both builders and manufacturers treat adobe as a product to sell, focusing on its positive aspects while downplaying its drawbacks. In contrast, I view adobe as a material needing repair and preservation, dealing primarily with homes in disrepair. Throughout my career, I’ve observed how these perspectives rarely align. Homeowners rarely call me when their adobe homes are in excellent condition.

Imagine for a moment: would an adobe homebuilder or manufacturer, who makes their living selling adobe, want to present the best possible scenario to their customers? Certainly; it only makes sense. No good salesperson will emphasize the negative aspects of their products—they will always highlight and accentuate the positives while minimizing or ignoring their downsides.

When I spoke with Smith at his business, it was because I was hired by the owners of Bluebonnet to repair their damaged home constructed with his earthen materials. He didn’t seem in the best frame of mind to welcome me warmly, which might explain his less-than-gracious attitude as I began questioning him about his failing product.

I recall a conversation with him about his asphalt-stabilized mud adobe. He asserted his adobe was engineered to last at least 100 years before showing any significant deterioration, claiming it would endure for a century while losing at most 1/8 inch of its surface. This statement was clearly an exaggeration, and I recognized it as such then, just as I do now. If he genuinely believed his own claim, it would indicate a serious flaw in his thinking.

The problem with Smith’s statement was that many—if not all—of his customers believed it. He was revered by many as an almost Moses or Pope figure, and, like both of these religious luminaries, what he said was almost on the same level as holy writ.

I don’t remember whether at that moment when Smith made this dubious statement I openly challenged him, but knowing my personality, I don’t think I would have let such an exaggeration go without at least some attempt at refuting it. At the very least, I would have made an appropriate raised eyebrow facial gesture of disbelief and astonishment. What I do know is Smith never seemed to like me after either of these two interactions we had.

I did purchase the material to repair the Bluebonnet house from Smith. He sold me the earth plaster mix as well as the asphalt emulsion used to impart a small amount of initial water repellency into the end product. I had a small mixer on hand that I used for other concrete and mortar projects, so I loaded it onto my truck and brought it to the job site to use in the mixing process.

As noted elsewhere on this website, the Bluebonnet house sat on top of a hill, offering expansive views. One afternoon, while working inside the house underneath a picture window where the thick earth plaster was also falling away, I removed some of the failing earthen material to make way for the new. In doing so, I inadvertently broke into a section crawling with termites, no doubt targeting the wooden window frames.

Smith incorporated wooden framing around the windows in many of his homes (seen in the picture below), a common architectural feature at the time, along with wooden headers over the windows. However, this design posed at least two significant issues: first, as mentioned, the wood attracted termites; second, wood and adobe expand and contract at different rates, leading to poor compatibility between the materials. In this particular house, where the adobe met the wooden framing, the continual expansion and contraction of the wood caused shrinkage over time, resulting in gaps between the two materials.

The choice of caulking material around the windows, often left to the discretion of carpenters or painters, proved pivotal in the longevity of the Bluebonnet house. Over time, the caulking deteriorated, allowing water to breach the protective layers of earth plaster and adobe. This infiltration not only inflicted visible damage but also enticed termites, drawn to the moistened wood framing. The resulting deterioration posed dual threats: structural integrity compromised by water and organic material compromised by pests.

The extent of termite activity inside this area of the house left me stunned—it was truly alarming. Yet, what proved even more startling was the sudden onslaught of a Tucson monsoon while I worked there. In a matter of minutes, torrential rain poured down, whipped by fierce winds and punctuated by thunderclaps that echoed through the house. The storm’s sudden ferocity stirred a primal fear, akin to Dorothy’s whirlwind encounter in “The Wizard of Oz,” leaving me half-expecting to be swept away into another realm.

Once again, I learned a crucial lesson about adobe construction: a home’s location significantly impacts its resilience against natural elements, particularly Tucson’s summer monsoons. Positioned atop a hill, the Bluebonnet house suffered the consequences of its unfortunate placement. Exposed to the full force of relentless storms and powerful winds, it endured severe battering beyond what was typical for the area.

This raises an essential point: every monsoon or rainfall event is unique. While the Bluebonnet house bore the full force of that particularly fierce monsoon, it doesn’t imply that neighboring homes on lower ground faced identical conditions. Perhaps these houses were spared the intense winds and heavy rains that made me fear for my safety, simply because they were not perched atop the same vulnerable hill to endure the storm’s onslaught.

Being directly in the storm’s path, the Bluebonnet house faced intense winds that uniquely affected its wooden window frames compared to neighboring homes. The property suffered heightened water damage as these winds drove rain through deteriorating caulk joints, worsening the destructive impact by saturating the porous adobe and earth plaster. This undoubtedly compounded the damage I needed to address. Observing the aftermath of that monsoon, it became clear that this issue wouldn’t be easily resolved, particularly in the face of recurring severe weather.

I’m sharing this background on the Bluebonnet house to underscore a straightforward point: John Smith misrepresented his adobe to countless customers over the years. I’m not claiming he was entirely mistaken, as I did encounter homes constructed with his material that remained in good condition for years and even decades after their construction.

Yet I witnessed numerous houses, such as the Bluebonnet residence, providing undeniable evidence that Smith’s claims regarding the longevity of his adobe were untrue in many instances. The issue here is many of his customers, trusting his misleading assertions, neglected proper maintenance, resulting in unnecessary and advanced deterioration of their properties. One of these common sense preservation recommendations he vehemently opposed was treating the adobes with a specialty water repellent, to the detriment of countless homeowners who suffered costly and unneeded deterioration of their homes by heeding his misguided advice.

Undoubtedly, Smith crafted and constructed quality homes. I admired his designs and material choices, aside from, perhaps, the wooden window frames. His use of asphalt-stabilized mud adobe was noteworthy. While not every home built with his adobe encountered significant issues, as mentioned, many of his properties remain in good condition and have stood the test of time. However, my concern lies with the portion of his homes which fell short of the lofty expectations he instilled in his customers, especially regarding the drawbacks and vulnerabilities of his adobe constructions.

Overall, I believe he produced decent adobe, with some batches being better than others. Rumors about various adobe builders, manufacturers, and repair tradesmen, like myself, are constantly circulating, so one must take everything heard with a grain of salt. One such rumor I came across regarding Smith’s adobes suggested their quality began to decline over the decades because he exhausted the premium soil for making his earlier adobes and had to resort to soil from another pit that didn’t meet the same quality standards. Consequently, the quality of his later adobes suffered. Is this true? I can’t say for certain, but it does seem plausible given what I have observed and experienced with some of his houses.

Allow me to provide you the latest example: On May 25, 2024, I received the following email from Michael:

Hi,

We have a 35 year old house made out of asphalt-stabilized mud adobe. After years of wind and rain, it needs some repair. Is this something you have lots of experience with? Or do you know someone who does? I’ve attached a picture so you can see what I’m talking about.

Here is the picture:

Immediately upon viewing this picture, I thought, “John Smith’s asphalt-stabilized mud adobe.” Notice the advanced deterioration of the surface of these adobes. One indication of “advanced deterioration” is when the outline of each individual adobe and the mortar joints that hold them together are no longer clearly visible. Look at the first and second rows of adobes immediately above the wooden window header to see what I mean.

In my reply email to him, I asked him if his house was constructed from Smith’s adobes. He replied, “Yes.”

I then asked if he could send me some additional pictures. Here are some of what he sent:

Though the picture appears washed out, you can still discern the extent of deterioration as you move down the wall. In some areas, the erosion is so severe that some mortar joints are no longer visible, and the distinct outline of individual adobes has been lost. Below is a closer shot for better clarity:

This closeup above further highlights the advanced deterioration of this portion of Mike’s adobe wall: the mortar joints have disappeared in some places and now, adobe and mortar joints now blend in together.

I wrote back to Michael:

“Your house appears to have suffered quite a bit of erosion; have you ever had it sprayed with a quality water repellent formulated for adobe like the Silox Adobe Water Repellent?”

His reply:

“The original owner sprayed it with some kind of silicone, but that was over 25 years ago. He felt it did more harm than good and I think [Smith] didn’t like sealers, so we have never retreated it. Our concern at the moment is repairing the adobe and doing something about the parapet to better protect the walls.”

Michael embodies the archetype of a loyal customer influenced by Smith and his misguided philosophy regarding “sealers.” For diligent readers of my website, it’s evident I never refer to the Silox as a sealer. Not wishing to repeat myself on this matter, allow me to direct you to this other page on my website which will explain this important difference.

I will agree with Smith concerning the use of a “sealer,” but cannot emphasize enough my disagreement over a silicone based water repellent. The former will help in the deterioration of an asphalt or cement stabilized mud adobe home while the latter, a specially formulated water repellent like the Silox, will help preserve it.

One of my former competitors in the adobe repair business (now retired after selling his business) once said about adobe home builders and adobe block manufacturers: “They are all criminals who should be in prison.” Although I find this statement harsh and overly broad, I understand his strong feelings. It’s hard to sympathize with those who knowingly sell a high-maintenance product that requires regular attention throughout the structure’s life yet fail to disclose this fact to their customers.

The fact is, adobe homes can be high maintenance, and in particular, adobe homes which are built in the Santa Fe style instead of in a ranch style (homes with a gabled roof that employ generous porches and overhangs [at least 4′ in width] around the home). See the first picture of this article showing a typical Santa Fe style home.

I have often wondered why adobe home builders and adobe block manufacturers refuse to acknowledge the deficiencies of their products. I believe it is because they are salespeople, and a good salesperson will emphasize the positive aspects of what they are selling rather than pointing out weaknesses. While this might be understandable when selling a pair of pants or shoes, where the worst outcome is funny looks or sore feet, it becomes a serious issue with building materials.

When it comes to our homes, the consequences of overselling can result in thousands of dollars in deferred maintenance and significantly impact the selling price if the homeowner decides to sell. Few home sellers have the financial means to pay thousands—or tens of thousands—of dollars for an adobe restoration professional to bring a dilapidated adobe home up to pristine selling condition before it hits the market. This is not like selling shoes.

Michael is a prime example, and I can provide many more. Worse, I am often seen as the bad guy for bringing bad news to customers who view men like Smith as heroes whose words are sacred and not to be questioned. It is human nature to stubbornly cling to the false viewpoints of someone we respect instead of being willing to change our minds when presented with contrary facts. Based on past experience with pointing out Smith’s clearly erroneous opinion toward water repellents, I will likely not hear back from Michael.

It’s important to note that Smith was not the only producer and builder of asphalt-stabilized mud adobe; he was one among many, some of who are still in business. From my long experience in this industry, most—if not all—of the people producing this kind of adobe, as well as those who manufacture its sister product, cement-stabilized mud adobe, share the same or similar attitudes toward their block as Smith did for his.

Consider Michael’s case multiplied by thousands of others whose homes were built with the same material. If their houses were designed in the Santa Fe style and have not been maintained with a water repellent like Silox every 5-7 years, I would predict at least 70% of them are experiencing problems on par with or worse than Michael’s.

Another customer contacted me in July of 2024, shortly after Michael did. Her home used Smith’s adobes and was built in 1986. She wrote: “…The house is sound and we have been very
happy with it.  At this time it is in need of some minor repairs, mostly filling of holes and some cracks that have developed. I have not found anyone to do the work.  Is it possible your company could help?  The exterior is not plastered but I am considering it.  I would appreciate any assistance you could give.“

I responded and requested she text me several pictures, shown below:

The picture above reveals significant surface deterioration for a home under 40 years old. While an untrained eye might overlook this, observe the distinct outline of each adobe block on the wall—they shouldn’t look this way. The earth mortar joints have eroded so much that the adobe blocks now visibly protrude from the wall. Notice the wall lacks protection from an eave, overhang, or porch, leaving it exposed to the full force of the weather. Here is another picture:

The customer sent me this picture (above) to show one of the cracks which developed in the wall. Not only is the crack extensive, but the amount of deterioration of the wall is troubling. Again, notice this wall is not protected by an eave, overhang, or porch. It appears the crack was at one time repaired because you can see the repair material in the crack, extending vertically, appears to be a different color than the surrounding mortar joints.

This is the third picture (above) the customer sent me. Notice it does not appear nearly as deteriorated as the first two pictures, though it is also not protected by an eave, overhang, or porch. But the picture does show this portion of the wall is a corner, which means the two walls making up the corner is providing each wall corner protection from the sun and certain prevailing winds and wind driven rains.

This picture is excellent because it demonstrates how much better this corner has been protected from the elements compared to the first two. Its more sheltered status has prevented the same degree of deterioration. While holes and general wear are visible, a closer examination shows each adobe brick isn’t protruding as much as in the previous pictures. This indicates significantly less erosion of the mud mortar and the surface of each brick.

These pictures provide ample evidence that Smith’s claim decades ago—that his adobe would endure for a hundred years with only an eighth of an inch of deterioration—was false.

I have always thought it would be helpful to gather all the home builders, architects, and manufacturers of sun-dried, stabilized adobe and unstabilized adobe in a large conference room. I would be invited to give a talk on my thoughts about adobe as a building material. Part of my presentation would highlight the concerns emphasized in this blog post. I would need much wisdom and a fair amount of tact to express my dismay over the sales tactics employed by many in the room and how they sell their product to homeowners who provide them with their livelihood.

I would emphasize the untold stress, agony, and needless expenses endured by adobe homeowners dealing with the myriad problems associated with this building material, problems exacerbated by the false or misleading information provided by those in this room.

I would delve into the psychology of why this problem is endemic to our industry and suggest that the root cause is greed. Greed? Yes, because I believe greed is the foundation of why this happens. If potential homebuyers were informed that adobe homes require regular, lifelong care and maintenance, many would likely choose another option.

But I would also offer hope. I would tell them this dilemma could be alleviated by honesty with their clients. Explaining that the love and mystique of living in an adobe home is so strong for some people, proper disclosure of the problems and expenses associated with this product would not be catastrophic to their bottom line.

For example, all homeowners know that the exterior wood portions of their homes need regular, lifelong attention. Take fascia, for example, exposed to the sun. This must be scraped, repaired, primed, and repainted every four or five years, depending on the home’s location. In Tucson, where I live, it might require maintenance every three to five years, especially if the fascia is on a home built on a treeless hill with southern or western exposure. This is common knowledge, and though nobody likes to spend the money on such projects, responsible homeowners know it is the cost of living in such a home and budget accordingly.

Why, then, is the same philosophy not extended and explained to adobe homeowners? Why not be honest with them and say something like: “Mr. and Mrs. Jones, you want to build an asphalt-stabilized mud adobe home using my materials. It’s a wonderful choice, a marvelous and ancient building material, but like all homes, it comes with maintenance costs that need to be closely monitored over the life of the home to best preserve your investment.

“The greatest enemy of adobe is water; the second is wind erosion. My adobe, like every other asphalt or cement-stabilized mud adobe made, is at risk of deterioration by these two natural forces. Like wood fascia on your home that needs regular monitoring and maintenance, my adobe is the same. You have to be diligent in making sure no water is being introduced into the walls through overwatering of plants, bushes, and trees, and no sprinklers are hitting the walls.

“You will need to treat your adobe regularly with a quality water repellent. But if you follow my recommendations, you will keep your adobe home in great condition and avoid the awful expense of needing to hire professionals to repair your home years down the line due to deferred maintenance costs.”

I was a real estate agent for a few years. In real estate school, we were hammered with the need to “disclose, disclose, disclose” to our clients. There is a form titled “SPDS,” which stands for “Seller’s Property Disclosure Statement.” It is so lengthy and detailed that it even asks the seller if there are any annoying noises that regularly occur around the home. Sellers are required to list roof leaks, past plumbing problems, insect infestations, etc. Failing to do so puts the seller at risk for a lawsuit if they sell the house and the buyer later discovers something that adversely affected the house that the seller failed to disclose in the SPDS. This is serious business.

Though I cannot confirm this rumor, I heard one reason Smith did not complain too much about the state forcing him to sell his property was because he was also involved in lawsuits concerning the numerous failures with his adobe. He saw the eminent domain situation as a “cloud with a silver lining” and got out while he could without losing too much face.

Smith was not the only adobe manufacturer who got sued by disgruntled customers; I heard similar stories about other companies facing the same problems. Like Smith, I have personally worked on the homes of other adobe manufacturers, and there are people out there who should not be in business. Many of them, perhaps most of them, probably felt as Smith did: if they fully and honestly disclosed to their customers the disadvantages associated with building with adobe, they would have fewer clients, translating into a loss of needed revenue.

I believe this mentality is both misguided and unwise. It is misguided because it fails to provide customers with the essential information they need to make an informed decision about purchasing the most important and expensive asset of their lives. It is unwise because, by failing to do so, sellers set themselves up for potential lawsuits that will come back to bite them in the end.

In closing, I feel strongly that our industry needs to change—must change, in fact. Such a change is long overdue, and I hope that by bringing this topic to light, I might help in some small way to right the wrongs the adobe industry has inflicted—either consciously or unconsciously—on customers.

If you have your own horror story of what happened to your asphalt stabilized mud adobe home and would like to share it with me, please email me at: adobemastr@gmail.com. Or call or text me at: (520) 331-4004. For more information on the Silox Adobe and Rammed Earth Water Repellent, click here.