“Repairing and Preserving Your Adobe Home”
by Roy E. Spears
copyright 2002-2023. All rights reserved.
Copying, pasting, editing, and/or sharing electronically without prior permission from the author is strictly prohibited.Chapter 3
“Should I apply a sealer to protect my adobes?”
This is perhaps one of the most controversial questions in the world of adobe, with strong opinions voiced on both ends of the spectrum. I am always amazed at the brilliance of arguments that come out of both sides of the question and can understand the viewpoints presented by both camps. Yet again, what is true for one type of adobe is certainly not true for all types of adobe, and this chapter will strive to put things in their relative perspective.
First, the case against sealing adobe, and at this point we must define at least three words to properly get a grasp on the issue: sealers, water repellents and breathability.
The first two, sealers and water repellents, are often wrongly used to describe two very different products. A sealer is far different from a water repellent; a sealer is a liquid (most of the sealers in past years were oil [thinner] based, but the majority are now water-based) that is applied to a substrate to make that substrate waterproof. The term waterproof also needs defining, for it is a term that is often carelessly thrown around and has come to mean something different that what the word actually means. When you waterproof an object, your intention is that you do not want water to come in contact with this particular item.
To illustrate this, let’s use a pair of boots as our example. If I want these boots to be waterproof, that means that I do not want to have wet feet when I walk through mud puddles in these waterproofed boots. Waterproof means just what it says, which is that water can not come in. None. Not a drop. I don’t want wet nor even damp socks when I walk through a mud puddle. I want completely dry socks, and this is why I wear waterproof boots. Webster’s defines this word as “that [which] keeps out water; so that water will not penetrate.”
Unfortunately, waterproof does not mean waterproof to many companies that sell their waterproofing products or services. The term waterproof has become so generalized and such an accepted part of our English language that we throw it carelessly around and use it to describe a plethora of things. No one is as guilty of abusing the true definition of the word than the big companies that make water repellents.
A water repellent does exactly what it says, i.e., it repels water, but repelling water does not necessarily mean that water will never get through. Let’s use the illustration of the boots again: if I choose to wear a pair of water repellent boots, expecting them to keep my socks dry, I will be quite disappointed in those boots if I spend any length of time sloshing through mud puddles. These boots may keep my socks dry for a short period of time, but the fact is, sooner or later, I am in for wet feet. Making something water repellent is not the same thing as making them waterproofed. Water will penetrate through a water repellent if the water steadily and continuously comes in contact with the surface of the item.
When you walk into Home Depot and look at a can of Thompson’s Water Seal (the one with the seal bouncing a ball on his snout), you will no doubt find the words “waterproofer” on there. But this is not true, for Thompson’s Water Seal is not a waterproofer but a water repellent, and shame on them for trying to sell you and I a product that will not do what the exact definition of the word states it will do.
Many people, not thinking about these play on words, assume, as I once did, that applying a product labeled a waterproofer on, for example, an adobe wall, will cause it to be impervious to the damaging effects of water. This waterproofer, after applying it in strict accordance with the directions on the label, causes me to believe that when it rains my adobes will never get wet. They will remain as dry as if this wall was built inside my house, surrounded by four walls and covered with a roof. Nothing could be further from the truth.
Why there is not some government regulation insisting that companies such as Thompson’s label their products truthfully is a mystery to me. Certainly this company, which I believe sells more water repellents than anyone else, knows that that they have not correctly labeled their product and are selling people something that will not work as the correct interpretation of the word would insist it would.
An interesting note on this is found in the June 2001 issue of Consumer Reports Magazine, on page 46:
“We can’t recommend the following products because of their poor performance: Thompson’s Water Seal and Water Seal Ultra and Wolman Rain Coat Water Repellent.”
A sealer is a water proofing product (to seal something means “to close completely, especially as to make airtight”), and a true sealer is a product that is called “film forming.” In other words, a sealer puts a film between your adobe and the elements so that when it rains, the “film” (something you can actually see) keeps the water from penetrating or from coming into contact with the adobe.
A water repellent, on the other hand, does not usually leave a noticeable or visible film on the surface, but leaves the surface, for the most part, natural looking. It penetrates into, or through, the surface of the material and is absorbed by the material. One would be hard pressed to tell the difference between an adobe wall that never had a water repellent applied to it and one that had, until water was sprayed on both of them. The wall that was never treated would immediately absorb the water and the surface would darken because of the water penetrating through its surface. The water sprayed on the treated wall would “bead up” and roll off, similar to what rain will do on the hood of your freshly waxed car or truck.
What many people do not understand about water repellents is that water will eventually bleed through the surface of walls that have been thus treated, if several conditions exist. First, no water repellent will stop water from coming through any surface where the water is continually and/or regularly thrown against that surface. A lawn sprinkler where the water is spraying on the wall every time the sprinkler system is activated is an excellent example of this. Nor will water repellents keep water from soaking into walls when the water is pounding against it, as typified in a thunderous, driving and continual downpour, such as what is common in Tucson’s summer monsoon season.
I enjoy those tests performed by many chemical companies and water repellent manufacturers to show how their products keep water from penetrating into the surface of bricks that have been treated with their particular products. In their advertisements, you will usually see little beads of water standing on the top surface of a portion of a treated sample brick or plank of wood, with water darkening and penetrating the untreated part of the brick or wood. It is impressive and convincing, and I have performed the same type tests with my own water repellents and have obtained identical results.
But having little beads of water dropped from a dropper onto sample bricks or wood in a laboratory is a long way from having a summer monsoon slamming against your house with gale force winds. No water repellent that I know of can withstand the force of such power, and to believe otherwise is to misunderstand the purpose of the product.
Water repellent chemistry is a sword that cuts two ways: on one hand they are what is commonly referred to as being “vapor permeable,” meaning that they allow trapped moisture to escape. It is a rare home (and probably non-existent) that is constructed with such meticulous care, expense and skill that it can be considered “waterproof”, especially when we are specifically referring to an adobe home. The simple nature of the material lends itself to imperfections, and when you start joining one burnt adobe brick with another using Portland cement mortar, cracking is a normal and expected—you are going to get cracking somewhere. Add age and wear to the building and it is a guarantee that somewhere in the history of the structure, water is going to get in from some point or another.
Knowing and accepting this, most chemical manufacturers and formulators have come to the conclusion that the best product for protecting the building from water damage is to apply a water repellent to the structure. When water does eventually seep into the building from a crack or some other entrance point, the best way for it to dry is for that same water to be able to escape back out. The problem of putting a waterproofing sealer on the adobe walls is that the moisture that will get into the building will not be able to escape back out through this waterproof coating. The moisture will remain locked inside the adobe and the damaging process of deterioration will begin.
Research has consistently proven that applying a waterproof coating to your adobe home is not the best of ideas. Once water gets into the substrate of the adobe and behind this impermeable coating, the pressure that the water exerts in striving to get back out can cause the skin of the coating itself to stretch, bubble out, then pop, break or tear. Occasionally, the surface of the adobe itself shears off, breaking away with the pressure of the water seeking to push through the coating. This water soaked adobe, unable to dry out thoroughly or quickly enough, simply begins to melt away behind the waterproof coating. The face of the block appears healthy, but a closer look reveals the coating bubbling out in areas. Piercing through these bubbles reveal a disintegrating block beneath.
This has been the continuing challenge of water proof versus water repellents. It is true that a waterproof coating is superior in its ability to keep water away from something than what a water repellent can. Yet the one benefit that makes these water proof coatings superior is the same benefit that can make them so destructive: they keep water out, but they also keep water in.
My opinion favors water repellent coatings over the waterproof coatings for three reasons. First, a waterproof coating is not invisible and will leave the adobe looking altered because of the shine the coating imparts to the face of the bricks. This is not necessarily unsightly, for a high solid semi-waterproof coating imparts a visible shine on the burnt adobes to bring out the colors in a richer and deeper fashion, which most customers like. But again, the factor that at first appears as a benefit (in this case bringing out the colors and giving the bricks a shiny, fresh look) is the exact thing that invites damage to the adobes. As previously discussed, water can be trapped behind such a coating and can accelerate and cause deterioration.
Second, waterproof coatings and semi-waterproof coatings degrade in the sun, particularly if the treated walls face the West and South and are not protected by porches or wide overhangs. These coatings, exposed to the harsh summer sun, begin to peel, turn a brownish color, and may need to be removed when they appear unsightly. Water repellents have no such problems, as they penetrate into the adobe and are invisible to the eye. When reapplication is necessary, you simply reapply the product and no laborious and expensive prep work is needed to remove the old coating.
Third, though water repellents are not as effective in preventing water from penetrating the adobe as a waterproof coating would, this is perhaps their greatest benefit. These water-repellent coatings will allow any moisture that penetrates into the surface to be released back out. It is my experience that water will penetrate into your adobe home sometime from somewhere because of something (cracks, age, damage to the adobes caused by tree limbs, insects, rodents burrowing in and through, birds and/or bees pecking and making holes, etc.). Allowing for this moisture to be quickly and harmlessly released back into the atmosphere is critical in the continued health of these adobes.
Perhaps the only exception to this is on those adobe homes that have the following characteristics:
l. A stem wall that lifts all the adobes at least 18″ – 24″ above grade
2. Landscaping and grading that directs water away instead of towards the home
3. Gutter systems that prevent rainwater from splashing back on the adobes
4. Continuous overhangs of at least four feet around the house and/or porches surrounding the home
5. Geographically located in an area where strong winds do not buffet the home and pounding rain do not slam against it (homes built on top of hills can have these problems)
6. No water hungry plants or planter boxes close to the perimeter of the house
A home with the above qualities is so well protected from the damaging effects of water and the elements that you do not need either a water repellent or water sealer anyway.
One truism I have personally experienced many times over is this: non stuccoed, Santa Fe style burnt adobe homes that have had water-repellent treatments regularly applied to their exterior walls rarely need any serious restorative work. The adobes themselves, if treated soon after the house was completed and then retreated every 3-5 years, are usually in very good to excellent shape.
Yet no water repellent, no matter how generously applied to the walls, will give adequate protection if the adobes are not first properly prepped; adobes which are crumbling, have surface “dusting” or “flaking” due to the outermost layer of the block itself deteriorating (particularly true of the parapet courses) will need to be prepped before the water repellent will give its maximum protection. For more information on the proper preparation of adobes, see Chapter 6 under the heading “Prepping.”