The Finish Line: Design Features
Height Above GradeIt’s not uncommon for designers to want to extend EIFS down into the ground at the bottom of a wall. This looks fine but it is not a good idea. EIFS is not a below grade insulation and waterproofing system, and will slowly disintegrate if used this way. But there are other factors. The codes, in many areas, require the bottom of EIFS to be at least 6 inches (or more) above grade. This is especially an issue in areas where termites are rampant, such as in the southern states.
One compromise is to use the EIFS coatings alone-with no insulation-applied directly to the concrete foundation wall. At least this retains somewhat the appearance of the continuity of the EIFS wall directly above.
Credit Card TrickOne of the keys to a crack-free EIFS coating system is to tightly abutt the edge of the insulation boards. If this is not done, the EIFS lamina may crack at the board joints. One easy way to inspect the fit of the EIFS insulation layer-as it is being installed-is to use a credit card. If a card will not fit between the edges of the insulation board, then the board joint is tight enough.
Parapet Caps Using Concrete or Cast StoneA number of my clients are sick to death of the following: the top of EIFS walls (that use EIFS as the parapet cap without any flashing) getting mangled by maintenance people. One solution is to make the cap from thin cast concrete or cast stone and cover it with EIFS finish. It looks nice and can take a beating from ladders and swing stages, etc.
Resin PercentThe glue that allows a good bond of EIFS to the foam and the wall comes from plastic resins, usually acrylics. The percentage of resin is not the same for all EIFS. Since resin is expensive, the minimum amount helps keep the cost down but there is a price to pay. Diagram 1 shows the concept.
When only a little resin is used in the product, the effect on performance is small. But when a lot is added the benefits do not make up for the cost. So the well-formulated product would have a resin percentage somewhere near line “A.” A less expensive product would be near line “B.” The problem with resin percentage “B” is that it does not allow for a lot of tolerance for mixing errors.
The moral: If the mixing or watering-down is too much, the performance suffers. With a higher resin percentage, the product is more tolerant of mixing errors. Don’t add extra sand, water or cement.
Glue-On SignageEIFS is a nonstructural cladding. It supports its own weight and resists wind forces. EIFS is not intended to have objects attached to it-especially heavy objects, such as flag poles and fire escapes. Heavy objects need to be attached through the EIFS and into the supporting structural wall system. But you can attach some very lightweight objects to EIFS.
Very light objects can be attached to the EIFS using a structural adhesive. This includes light objects like small plastic address numerals on homes. Using an adhesive is faster and less expensive and bypasses the problem of drilling holes through the EIFS, possible water intrusion and fastener corrosion stains.
Acrylic Sealants: Bond Vs. StretchinessMany EIFS coatings, including the basecoat and finish, use acrylic resins. Naturally, acrylic-based adhesives and sealants adhere well to these EIFS materials. By acrylic, I mean sealants that are mostly acrylic and not a blend with some other sealant material.
Acrylics get stiff when they get cold and when a sealant joint opens up (when the temperature goes down), the movement can exert enough force on the EIFS coatings to pull apart the surface of the EIFS. This can lead to leaks. Thus, acrylics are best suited for small joints that are not subjected to a lot of movement, such as around small windows in homes. For large joints, such as between prefab EIFS panels, a softer grade of sealant is needed, such as a low modulus silicone.
Barbeque GrillsI’ve been on a number of condo projects where the owners were griping about the EIFS being “dented” or “weak” on their deck. It takes 30 seconds to note that they have their BBQ grill pushed up against the wall where the dent was. The problem is that the heat from the grill gets transmitted through the EIFS coatings and melts the foam insulation. The EIFS coatings are then unsupported and sag.
WoodpeckersThese cute but frisky little buggers can be a real hassle if you live in an area like I do (in the southeast U.S.).
Why EIFS? They seem to like the sound of bashing their beaks against EIFS (sounds like a decaying tree, maybe?). Once through the EIFS lamina, they find soft foam insulation. They auger out the foam and create an insulated nest. Then you have even more of them. You can hear them indoors at night. What to do about this?
Many woodpeckers are endangered, protected species, so you just can’t shoot them. Some species migrate, and once you think you’ve scared them away, they come back next year. Fake owls and snakes don’t fool them either. Firearms and other forms of death are illegal in most area. There is no easy solution to this problem other than harsh language and prayer.
Painting EIFSIf painting EIFS (to change the color or generally improve the appearance), be careful what kind of paint you use. Water-based paints work best and EIFS producers make paint versions of their own finish coatings. Also, some EIFS finishes have water repellant materials in them that make the adhesion of additional layers, like paint, difficult.
Also, if you use a highly water repellant paint, it can seal the outside of the EIFS from water vapor flowing outward from indoors. EIFS coatings are breathable and if the vapor flow is stopped by a hard, impermeable paint, condensation may occur within the wall.
Rust in EIFS FinishOnce in a while, the rough “texture particles” in an EIFS finish become contaminated with iron. The iron is a tiny ferrous inclusion in the sand texture particle. After being on the wall, rust spots can develop in the form of streaks. This is especially common in hot, humid, salty environments like the Gulf Coast. These particles can be removed by picking out the offending particle and then removing the stain with a commercial rust remover. This is a lot of work.
If the wall is full of rust spots, sometimes painting is tried as a quick cover-up. Often this does not work, as the rust “blooms” through the thin paint layer again anyway. By applying a new basecoat and finish over the existing EIFS lamina, the rust can be permanently buried.
V-Shaped Aesthetic Reveals: Cracking, Water Flow and StainingV-shaped aesthetic reveals (joints) are a convenient way for designers to give a modular panel effect to a façade. However, they also present problems (see Diagram 2), a vertical section through a horizontal V-shaped aesthetic reveal.
First, water flowing down the wall is diverted into the joint area via Area 2 to Area 1. The resultant dirt in the water then stays in the joint and then-the next time it rains-flows out through Area 3 and deposits the dirt as a stain on the façade. That’s not all.
The constant movement of the vertical face of the EIFS coatings makes the bottom of the V-groove at Area 1 act like a hinge. This can cause cracking. Then the water that is running down ends up being directed into the crack, leading to leaks. Further, the use of a flat sharp-edge metal trowel-when used to push the mesh into the groove-tends to sever the reinforcing mesh, making it extra vulnerable to cracking.
The moral is to use rounded aesthetic reveals and to use a profiled trowel to press the mesh into the aesthetic reveal.
Recessing Sealant BeadsReplacing failed sealant joint in EIFS-especially with EIFS prefab panels-can be a meticulous process and expensive. One way to lessen this cost is to initially design the joint where the sealant is not at the face of the joint but rather is recessed back in the joint. This does change the appearance of the joint but does do two key things:
It protects the sealant more from sun and weather.
It allows replacing the old sealant without removing it. The new sealant can be applied over the old one.
Humid Indoor Spaces Vs. Insulation JointsBeware of EIFS applications where the indoor space is very humid. The moisture indoors will naturally try to work its way toward the outdoors by flowing through the EIFS. If the joints between the EIFS insulation board joints are not tight, the moisture will come through to the surface, darkening the areas at the edges of the boards.
I’ve seen this numerous times, and the worst example was a mushroom growing factory with a closed humid indoor environment. You could see every insulation board in the EIFS-it looked like a checkerboard.
Next month’s column will present a whole range of other “good-to-know” aspects of EIFS that will help you to create better performing EIFS buildings.