There's a good bit of EIFS on the central Gulf Coast, including some large casinos and hotels right at the water's edge. Some of these EIFS got clobbered so bad that the walls simply aren't there anymore or are so damaged that the walls will have to be removed and replaced. There are also lots of EIFS jobs that got hit head on and appear fine. EIFS is a surprisingly tough product.
As I see it, there are two main issues for EIFS walls as a result of Katrina: structural damage due to wind and various types of water damage. Here's how I see this situation unfolding.
First, I suspect that the most sinister problem will be damage that is hidden and never dealt with. This includes EIFS that is no longer properly attached and problems lurking within wall cavities.
Waterlogged woodThe problem of the EIFS being properly attached to the wall structure is hard to assess, as a fully attached wall doesn't look any different than one that is barely hanging on. Obviously, bulging and displaced wall areas can be spotted but that's not enough. There is a test method for "pulling" on EIFS walls to see how well the EIFS is attached, and this test was mentioned in a previous Finish Line article. No doubt this technique will be employed on some buildings affected by Katrina.
In this method, a plywood plate is bonded to the EIFS finish and a winch applies a pulling force to the EIFS. The force that is being applied is measured and can be converted to "pounds-per-square-foot" of load capacity. As wind loads increase with height above ground and are higher at corners, this test is best suited for tall buildings. It's obvious from the aerial photos of New Orleans, for instance, that there are vast areas of one- and two-story houses that are somewhat protected by their low profile. These buildings have a different problem.
The problem with these houses is that many are light wood frame structures and they have been at least partially under water for weeks. Expressed another way, leaks are not the same as long-term flooding. Many building materials can withstand the effects of a sudden water exposure that occurs quickly and then goes away. An example would be a flash flood. What we have with Katrina are walls that have been soaked to their core for weeks and a lot of common wall materials, especially those that are wood or gypsum-based, cannot stand that type of exposure-they fall apart.
If an adhesively attached EIFS is found to have become detached and if the substrate is still sound and drillable, then the EIFS can be mechanically reattached. The technique uses normal EIFS mechanical fasteners and drives them through the entire old EIFS and into the substrate. The fasteners are overdriven slightly to make the EIFS lamina compress and to make the fastener washer flush with the old finish. Then an entire new basecoat (with reinforcing mesh) is applied over the old finish. A new finish is then applied over the new basecoat. The old finish needs to be cleaned carefully to ensure good adhesion. It also helps to use a cementless basecoat adhesive, to obtain maximum bond. You do need to apply a new basecoat-simply putting a new finish over the old finish will not work-it will chip off at the fastener washers.
With EIFS walls, there's another issue that is somewhat particular to EIFS. EIFS walls are essentially sealed structures. There are few, if any, seams and thus, there is little ventilation of the wall cavity. Hence the only way for moisture to disperse is to the inside (through the drywall) or to the outside (by going through the EIFS). Both these processes are slow, especially because some stud-wall materials absorb moisture and don't give it up easily. Also, remember that the Gulf Coast is a hot, humid area so there's little drying tendency, as the air is already full of humidity and doesn't easily accept additional moisture. Consider how different this situation would be if it had occurred in Phoenix, where the leftover moisture would literally be baked out of the wall by the dry hot climate.
This poorly ventilated aspect of EIFS walls, in contrast to, say vinyl siding, which has thousands of feet of seams, all of which "breath" a little. When EIFS walls get really wet, either from massive leaks or flooding, they can take an eternity to dry out. This can lead to long-term deterioration of wall materials, as well as reduced insulation efficiency and mold/mildew. However, this is not solely an EIFS problem in the case of Katrina; there is simply so much water that any type of wall will take a long while to fully dry-out. This drying aspect of EIFS walls that have been soaked is a subject that deserves some immediate study in terms of the long-term viability of the wall and possible health effects. This would help people involved with rehabilitating the building decide how to approach the repair process.
Contaminated waterThere's also the issue of what "kind" of water was in the wall. It's no secret that the water in New Orleans is contaminated with all sorts of bad stuff, not the least of which is human waste, bacteria and God knows what else. This residue, if left in an enclosed warm space like a stud cavity, can easily fester into mold and mildew. Simply working on these flooded structures is a bit daunting for contractors, as they have serious health issues to contend with. This may turn out to be a critical aspect to the speed with which the affected communities can be rebuilt. Honestly, it's also a little spooky to me too, as I expect to be poking around in these building, surrounded by this soup of smelly floodwater.
To me, all the above wall issues point toward removing the interior finish, like the drywall and plaster, to get at the problem. This would allow cleaning out the cavity, inspecting the framing and sheathing, checking the wiring, and replacing the insulation. And, most important, it would let the wall dry out much faster. It would also allow the outer part of the wall to remain in place (assuming it is OK), thereby keeping the weather out and maintaining security.
As far as replacing the EIFS that has been submerged and is no longer properly attached to the wall, I would be tempted to strip off the entire EIFS and the sheathing to a point a foot or so above the high water mark, and reinstall new EIFS. I think I'd use one of the new EIFS with drainage products.
Luckily, EIFS materials, including the adhesives, finish and insulation, are not particularly water absorptive, although water can be forced into foam insulation by water under pressure (as when submerged). This water takes a long time to go away and dramatically reduces the energy efficiency of the insulation. To see if EIFS insulation is waterlogged, it's just a matter of removing some large pieces, peeling off the EIFS lamina and weighing the sample. The density of the foam (or the foam plus water) can then be calculated to see how much added weight the water, if any, has contributed.
In terms of using EIFS again to replace damaged EIFS or to replace some other cladding, EIFS can be designed to withstand wind forces, like hurricanes. It's mostly a matter of having a strong substrate and beefing up the EIFS' attachment systems. Adhesively attached EIFS are stronger than mechanically attached but have the down side of possibly having the adhesive or the substrate affected by water. Mechanical attachment is thus more "permanent" in a sense, provided that the substrate does not itself fall apart and that the fasteners do not have too much corrosion. The problem with mechanical attachment is that the EIFS foam insulation is a relatively weak material and it is hard to get enough fasteners into the foam to get a good grip onto the substrate. Hence, when designing for very high hurricane wind forces, adhesives are the way to go. With adhesives, the wind force is spread out more uniformly across the foam and hence, higher attachment strengths can be achieved.
I noticed a lot of blown-out windows on the TV and now would be a good time to upgrade the glazing. On homes, the dominant type of window has a nail flange to mount the window onto the face of the sheathing. On EIFS houses, to retrofit this type of window would require cutting back the EIFS around the window. However, to avoid this extra work, it may be possible to remove the old window without cutting away the EIFS and then using a box frame-style window in lieu of the nail flange type. To say the least, this would also be a good time to install proper flashing and caulking joints around the window, especially at the sill.
The level of destruction due to Katrina is unprecedented and no doubt it will be many months before the affected areas are back in any sort of normal shape. For Walls & Ceilings readers, there will be a huge challenge of providing the materials and labor to deal with the repairs. As of the second week in September, when this article was written, I've received many requests to come assess the condition of EIFS buildings affected by Katrina. Even two weeks after the storm, there really is no place to "go" or even to stay (try to get a hotel room anywhere in the region). Thus, I am currently in a standby mode until the wreckage is cleared and it's safe to enter the area. I'll keep you posted as I get to work and learn during the rebuilding the EIFS jobs on the central Gulf Coast.