There are quite a number of reasons why EIFS manufacturers get specific about the conditions under which their product is to be installed. This month’s column will give you some tidbits of information so that you can respond to architects, GCs and others who try to push you to install the EIFS when the conditions are not right.
Dry and cureFirst, let’s clarify what we mean by drying and curing. Some people consider drying to be the process by which the water in a material, such as an EIFS finish, evaporates. It’s the same process that occurs when applying latex house paint. Some people define curing differently from drying. Curing is often regarded as a chemical process involving a reaction between several materials that results in the mixture taking a new form. Usually, that new form is a harder, more rigid material, rather than remaining as a liquid or paste. Such is the case with Portland cement-based EIFS adhesives. For purposes of this article, I’ll call both processes “setting up.” I have yet to see an EIFS finish that sets up by curing; finishes dry.
Setting up by drying is temperature and humidity dependent. Low temperatures and high humidity make the process take longer. Curing is not so temperature sensitive. This is one of the advantages of Portland cement-based EIFS adhesives, such as are used in attachment adhesives and basecoats. In essence, the setting process is more predictable; you know that it will have “set up” in a certain amount of time. For instance, in cool damp climates, such as those that exist all winter where I live in Seattle, cementless EIFS adhesives take an eternity to dry. Obviously, this can cause problems with the constructions schedule, since you shouldn’t apply the next layer until the one beneath it has set up. The converse can be true, too. In hot dry weather, the finish can set up so fast that you don’t have time to work it.
This can create major color and texture problems. This problem is a little easier to solve than the cool-damp problem; simply provide some shade.
The cool damp problem is mostly an issue in northern climates, in the fall and spring. In the winter, it so cold so much of the time that the job has to be tented-in and heated if any work is to proceed. Fall and spring, being transitional seasons, are the troublesome ones that provoke the above mentioned phone calls.
One of the basic questions about the standard 40 degrees F minimum application temperature is “Why 40 degrees F? Water freezes at 32 degrees F.”
The answer is simply that the formation of the plastic resin film that takes places when a cement-based or cementless material sets-up does not occur properly below about 40 degrees F. Suffice to say that too low set-up temperatures can cause problems such as poor adhesive strength, poor water penetration resistance, and so on.
It’s not just a matter of the temperature of the air, either. The surface to which the EIFS material is applied also needs to be 40 degrees F or above, and needs to stay that way for 24 hours. This is because even if the EIFS material is, say, 60 degrees F (having been stored in a heated area) when it comes in contact with the cold surface, the coldness of the surface will draw the heat out of the EIFS material, thus lowering its temperature. The EIFS material, being thin, does not have much heat storage capacity, so when applied to massive, cold substrates, such as concrete, its temperature can drop too low quite quickly. A concrete wall, for example, may be well below freezing, but still look “normal.” The problem is similar to what happens when you pour water onto an ice cube. The poured water freezes on contact. One can measure the temperature of the wall’s surface easily with an inexpensive electronic contact thermometer.
A similar situation can occur if it gets too cold right after the EIFS material is installed. EIFS basecoats and finishes are thin, and if the temperature drops overnight, the EIFS material can quickly loose its heat, and possibly even freeze. Water expands when it freezes, and this can wreak havoc with the proper formation of the plastic resin film within the EIFS material.
Not so coolThe situation is a bit better, in some ways, with attachment adhesives. The good news is that the adhesive is protected from the possible coldness of the outdoor air by the EIFS insulation; the insulation helps maintain the temperature of the adhesive. Thus, it tends to lose its heat less rapidly, and can set up properly. The bad news is twofold. First, the substrate may be cold, and the interior of the building is probably not yet heated, so the substrate itself may become cold from the inside. Second, if using a cementless adhesive, the loss of water that it required for the adhesive to dry does not occur quickly since there’s no where for it to go; it needs to evaporate to somewhere, and the EIFS insulation and the substrate are in the way. One way around this predicament, when using wood-based sheathing substrates that require cementless adhesives, is to use mechanical fasteners instead of adhesives. The mechanical fasteners also allow you to put on the basecoat right away (after you’ve “spotted” the fastener heads), as there literally is no adhesive that needs to dry.
When tenting-in a work area and providing supplemental heat to increase the temperature of the wall, keep in mind that heat alone is not the only issue. Ventilation is also required to remove the moisture from the work area as it is liberated from finish as it dries. It’s even possible for the humidity to get so high in the work area that the protective tarps drip with moisture. This can lead to water flowing onto the not-dry-yet finish, leading to color and texture problems, or even washed-off areas. Also, keep in mind that devices that produce heat via a fuel combustion process can also add water to the air, as water is a by-product of combustion. Hence the need to ventilate the work area and to supply warm, dry air.
Once in a while, I get an inquiry about the availability of EIFS adhesives and Finishes that are solvent-based rather than water-based. Solvents have a lower freezing point than water, and thus EIFS materials that use solvents could conceivably be applied at lower temperatures. The reasons solvents are not used are numerous. Cost is one issue; solvents cost more than water. Another major issue is health and safety: exposing the environment and workers to solvents fumes, how to dispose of left over materials, and so on. It is possible to make EIFS materials that use solvents, but considering that water-based EIFS materials perform just fine and are cheaper, why bother?
Lastly, obviously material that is frozen solid cannot be used as is, or should not be used even when it has thawed. However, it takes more than a dip below 32 degrees F at night to freeze a bucket solid. A 5-gallon pail has a lot of mass, and it takes awhile to cool it down enough to freeze it. Just because the weather dipped into the low 30s does not mean that the pails in the trailer got too cold. All it takes is a little bit of heat to keep them safe. When EIFS material have been frozen solid though, they often smell weird and have a funny consistency. If you apply them, they may appear OK at the time, but later they may lack water resistance or the finish may not stay stuck to the basecoat. It is possible, although difficult, to look at EIFS materials that are suspected of having been frozen and determine if they have been frozen. This can be done both while they are still in the pail, and also once installed. For instance, if the basecoat is frozen when the finish is installed, you may literally see ice crystal patterns on the surface of the basecoat. Another hopeful technique is to send samples to a qualified lab, and try to compare properly cured (or dried) materials with ones that are frozen. This can be a complicated and often inconclusive project. In the end, the best approach is simply to just follow the manufacturer’s instructions, and keep good notes about the weather. W&C