The Evolution of EIFS With Drainage
This seems a bit odd because it infers that adding drainage to EIFS alone will solve the problems of a leaking wall assembly. Clearly, drainage is only part of the solution. For instance, what about flashings, windows, sealant joints (or lack thereof) and so on?
Be that as it may, the use of EIFS with drainage became mandated on wood-frame buildings in many areas. Since then, the use of EIFS with drainage has spread to buildings where its use is not required. In fact, some EIFS manufacturers are promoting such uses, such as on commercial buildings.
In my consulting work, I frequently get asked, "How do I do such-and-such a detail with EIFS, if I want to use EIFS with drainage?" This month's column is a compendium of some of the more interesting and important issues that have come up. Some are not too hard to address and others are unresolved. Hence, many of these conditions are part of the evolution of EIFS with drainage into a more mature EIFS product type.
Resist high temperaturesAt some place in an EIFS-with-drainage wall, the water needs a way out. Window heads are an obvious location. Sometimes, plastic and aluminum trim, embedded into the horizontal bottom edge of an EIFS assembly at a window head, are used to make a clean termination. Herein is the issue: What happens if a fire comes out the window and melts the trim? The answer is that the EIFS lamina will come loose and perhaps the fire could get at the foam, causing the foam to burn.
In conventional EIFS (a.k.a. barrier EIFS) this does not occur if the window head is backwrapped. The reinforcing mesh is tough enough to withstand the fire. This can be shown in the multi-story fire tests required by the codes to permit EIFS on noncombustible buildings.
What's the solution? Perhaps it is to use a trim material that is resistant to high temperatures. Plastic and aluminum are not resistant enough but steel is. Another approach is to route the water, if possible, to the sides of the opening, so it can continue to flow down and eventually out. However, this doesn't work if there are long continuous runs of strip windows.
EIFS panelsOne of the beauties of panels made with conventional EIFS is that they simply butt up against each other (and against other wall elements). Things are different with EIFS with drainage. The difference is that the drainage cavity is back near the substrate and the water needs to be routed to the outside face of the panel. Clearly, a normal panel sealant joint would block any exiting of water. Also, some way of getting the water out to the face of the panel is needed, such as a flashing.
Here's the rub: Flashings look ugly and I've had many architects say it's a deal breaker because it's so unattractive. Plan B might be to marry the water barrier of an upper panel to the top of a lower panel, thereby sending the water-if any-downward, where it will, at some point, be routed to the outside. At some point, one has to ask, "How many stories can I get away from this?" I can imagine a wall wherein the drainage cavity never really dries out. No doubt, this would not be good for the wall.
One clever partial solution I've seen to making panels using EIFS with drainage is simply to make them as large as possible. Obviously, there are limits regarding handling and transporting megapanels but the point is this: By having fewer joints in the panels, which the need to route water to the outside occurs less often. And, if there is a want to still try to maintain some sort of modular groove appearance on tall narrow panels, one can use aesthetic reveals to create the appearance of panel joints without having to actually have real joints.
This whole issue of how to marry the often complex flashing, sealant tape and sealant interfaces at the edge of adjacent EIFS panels, and still maintain the continuity of the water cavity, is a thorny one. I heard horror stories of people experimenting with flashings that built-in the panels and that are supposed to be connected to mating flashings on adjacent panels during panel erection. The result is mangled flashings in-transit, and frayed nerves trying to connect all these materials together. This brings us to the next issue.
Big cavitiesIn some parts of North America, there's a fascination with having large drainage cavities. Tests show that a small cavity, in the range of 1/2 inch, is enough to let water move downward quickly. So why have a big cavity? I do not know but it appears to come from the idea that a bigger cavity drains more easily (it would) but also that the EIFS becomes more of a "screen," and thus one can create a rain screen type wall design using EIFS. There are a couple of major issues with this.
First, EIFS works as an insulation material because it is outboard of the supporting wall while also being simultaneously essentially in contact with the supporting wall. If a large cavity is used, air currents develop within the cavity, causing loss of insulating efficiency.
Second, and more important because it is a safety issue, is this: If a fire gets into a big cavity, the cavity might act like a flue, allowing fire to spread upward within the EIFS because air could move within the cavity, feeding the combustion process. This is potentially a serious matter and should be tested. There are large-scale fire test methods that can simulate the performance of this type of design and before I'd put my name on a wall like this, I would want to know for sure it is safe. At the very least, the backside of the foam would have to have some type of protection from fire, instead of being left "raw." This would be fun to try to construct.
Sills and soffitsSometimes, EIFS walls on commercial buildings look like the illustration in Figure 1. Assuming that areas A, B and C are all clad with EIFS, which ones need to be, or should be, EIFS with drainage? And, better yet, how does the water, if any, get out and where? Clearly area D is where water, if any, moving within area B, would want to be exited, rather than bring it back toward the window. Exiting the water at area D requires some sort of opening in area D but does area C need to be EIFS with drainage? This is worth talking about with the code people, since the codes do not address the issue of "having to use" EIFS with drainage on wood-frame buildings in the sense that their viewpoint is focused on vertical surfaces.
Critters at gradeIt's an understatement to say that in some parts of North America, critters (such as termites) can be a real hassle. With EIFS with drainage, the lowest horizontal edge of an EIFS wall is often above the ground. Since this edge is open to allow the wall to drain, it also is an entryway for termites. Some EIFS with drainage designs provide drainage at this point using a continuous open slot. This could let in an army of termites. If embedded trim is used with tiny perforations (to allow the water out) then one gets what is needed: drainage and bugproofing; but the perforations need to be small.
One solution I've seen to this (sort of) was in Australia, a country that happens to have a disproportionate amount of nasty, crawly, poisonous creatures, especially spiders. The Aussie answer is to take stiff stainless steel screen and bend it, as if it were sheet metal, into the shape of an "L," and attach the vertical leg onto the face of the substrate and to embed the horizontal leg into the basecoat on the edge of the foam board. Looks nice and doesn't rust either.