Leaky EIFS: Coatings and Primers
One of the constant comments that you hear about EIFS is that “it” is leaking. The “it,” in this case, is the EIFS itself. In the more than 20 years I’ve spent dealing with the technical aspects of EIFS, I can count on my hands the number of EIFS projects I’ve seen where the EIFS coatings themselves were actually leaking. Such occurrences are exceedingly rare. The leaks almost always occur where the EIFS meets another material, such as at a caulking joint, or via an adjacent wall component, such as a window.
However, there are times when the EIFS coatings themselves do leak. You may want to guard against this possibility for the future, or fix an existing problem. This article will give you some tips on how to deal with this commonly brought-up, but rarely true, situation.
For purposes of this article, primers are defined as coatings applied over the cured basecoat before the finish is applied. Usually such materials are applied with a roller and a brush, but some can be sprayed. Spray-applied primers, however, tend to be magically deposited on lawyers’ black BMWs five blocks away. So to avoid losing your life savings to those extortionists who belong to The Bar, stick with rollers and brushes.
Primers are available from almost all EIFS manufacturers. Some manufacturers even heartily endorse their use, but few require them. Not requiring them is unfortunate, since they serve many useful functions. In fact, primers are mandated by EIFS manufacturers in many areas in Europe because they do demonstrably improve the performance of an EIFS. Here’s how they do so.
Try this experimentNext time you’ve got a Dixie cup’s worth of spare EIFS finish, trowel it onto a piece of clear glass or Plexiglas. Let it dry, and then hold it up to the light. What you’ll see are light and dark areas. The dark areas are where the finish is thick and opaque. The thin ones are where the finish is thin and translucent. What does this tell you? It actually means two things.
The first is that unless the basecoat is the same color as the finish, the color of the basecoat will tend to affect the perceived color of the finish; the basecoat color shows through in some areas. This can result in a apparent color change to finish. This can cause color-sensitive architects and owners to freak out and make a big deal over nothing. Since the basecoat color is rarely the same as the finish, and because basecoats, especially cement-based ones, do vary in color, the finish can look mottled because the background over which the primer is applied varies. A primer can improve this situation by providing an even, constant color over which to apply the finish.
The second is that the finish is so thin in some areas that it provides almost no water penetration resistance. This means that the basecoat must do the full job of keeping water from getting to the insulation layer. Applying a primer over the basecoat provides another layer of “sealing” to the EIFS lamina, thus improving the water penetration resistance of the entire EIFS.
Applying a primer has other advantages, too. It makes more uniform the surface to which the finish is applied. This makes applying the finish easier, and also improves color control in another way: It makes the water absorption of the basecoat uniform, thereby making the drying of the finish occur more evenly. This, in turn, makes the color of the finish more uniform.
Let’s assume that for some reason the EIFS lamina is not waterproof, and that water is getting through it to the insulation layers. The type of insulation used in EIFS is not 100-percent waterproof. I use the term “waterproof” with care, because these materials can absorb moisture. These preformed boards of insulation also have seams between the board pieces, which can be a direct avenue for moisture to get past the insulation layer to the substrate.
There are many reasons that the EIFS lamina may not be doing a proper job of shedding water. A common one is that the lamina has not developed its properly waterproofing properties due to some kind of error when it is erected. An example can be a miscalculation in the amount of water or cement used to make the basecoat. This can result in a basecoat that it porous.
The porosity of the lamina can be checked in a number of ways. One way is with a simple device known as a RILEM tube (pronounced “ry-lehm”). A RILEM tube is an open-ended clear glass or plastic tube that is shaped like an “L.” The lower, shorter leg of the “L” is adhered to the area in question and the vertical leg is filled with water. The water exerts pressure on the lamina. If the water levels start falling, it means the water is leaking through the coatings.
Ways of testingYou can also determine water penetration resistance by removing a chunk of the EIFS from an existing wall and laying it horizontally on a table. You then glue a straight glass tube to the finish and fill it with water. As with the RILEM tube, if the water level gets lower, then the water is getting through the EIFS lamina. In both cases, be sure to cover the open end of the tube so evaporation is not the cause of the lowering of the water level.
Yet another way to determine water penetration resistance is to remove a chunk of the whole EIFS from the wall and carefully remove the insulation all the way to the backside of the basecoat. Then seal the edges of the sample with a waterproof material, such as wax, and float the EIFS chunk in a tray of water, with the hole side up. If water is getting through the lamina, a wet spot will appear on the backside of the basecoat. A variation of this test is used in Europe as a simple way of testing the waterproofness of EIFS lamina.
Since, on an existing EIFS wall, adding a primer between the finish and basecoat to improve water penetration resistance is not feasible, a common solution is to apply a coating over the finish. This technique is very common, and is especially rampant with inexperienced EIFS investigators who jump to the erroneous conclusion that the lamina itself is indeed leaking. If it is, then applying a coating can solve the problem. If however, things are normal and the lamina is not leaking, then the real source of the leaks will not have been attacked and the fix will be ineffective.
Elastomeric coatings are commonly used to seal the outside of an EIFS. (They are made by both EIFS manufacturers and coating manufacturers.) Be careful to use one that is compatible with EIFS. Some coatings are solvent-based and can react with the EIFS coatings and the insulation. Water-based coatings are the way to go. Some coatings also have very low water vapor permeability. This can induce condensation into the wall when none occurred before.
Be especially cautious in areas with cold winter temperatures, as the moisture tends to condense in areas that are in the cold, outer portion of the wall. This can, for instance, reduce the adhesion of the lamina to the insulation, or effect the bond of the insulation to the substrate. If in doubt about what type of coating to use, check with the EIFS manufacturers first. They can also help you determine if condensation will occur by running simple engineering calculations.
Although the additional of a primer between the basecoat and the finish is another step, and adds some cost, it does result in a better EIFS project. The application of the primer occurs quickly and requires little skill, so it need not be a budget-breaker. It can also be used as another tool in your arsenal of EIFS facts that can help convince architects and owners that extra steps are being taken to keep at bay the ogre that keeps haunting the EIFS industry, namely, annoying mantra that “EIFS leaks.”