An EIFS weather barrier is the same as putting building paper around your house, isn’t it? You can just slap it on and you’re safe, right? Yes… and no. Yes, it is a weather barrier which will keep moisture away from your substrate. No, it’s not the only component of a well constructed weather barrier. EIFS has gone through the fire of criticism and condemnation, and come out the other side stronger than any other cladding. It has undergone so much research and testing that it is now correcting faulty building methods in all other sidings as well as professionals’ understanding of their homes. A full weather barrier incorporates not only the weather barrier itself, but also caulking, flashing and window-tie ins in their respective location to keep water at bay.
Around any penetration in EIFS which may move (eg. hose bib, wiring, electrical meters) or openings which may expand and contract at different rates (eg. windows and doors) you will need caulking and a backer rod. Dissimilar materials expand and contract at different rates, causing rigid materials between them (such as a basecoat) to crack and leak water inside. Low-modulus caulking will expand and contract significantly before tearing, making it an ideal material for these gaps. However, caulking will only properly move when adhered to only 2 surfaces, therefore a closed-cell backer rod is required between the gap to provide a third surface, to which the caulking will not stick. It is recommended to caulk between the EIFS and other surface before applying the finish coat, as the caulking will not properly stick to finish coat.
Low Modulus Sealant Adhered to 2 Surfaces and Backer Rod
Look around at homes in your neighbourhood next time you’re out — how many windows have flashing over them? Water running behind claddings, then into the window frame is one of the most common causes of moisture problems in homes. Installing “kick out” flashing over a window will “kick out” any intruding water before it enters the window frame, preventing it from traveling any further down the substrate. Flashing needs to be installed starting behind the weather barrier, extending beyond the window frame, with a minimum 3/8″ drip edge (+ return) and sealant on the underside. It’s a good idea to get a color close to your stucco wall or trim (you likely won’t match it exactly) to blend in and minimize any aesthetic disturbance.
An additional step recommended by EIFS manufacturers (though rarely installed by applicators without proding) is window tie-ins using EIFS tape. EIFS tape covers from the outside weather barrier, across the window opening/framing and into the interior to completely seal the substrate, window frame and interior drywall from water intrusion. It is usually supplied as a peel-and-stick membrane (like duct tape), minimizing the time it takes to install and lower the chances of improperly installing it. It is worth asking who will do this as it is not normally within a stucco contractor’s scope of work.
Traditionally, it was uncommon to see flashing and window tie-ins on homes, and caulking (and the previous two) were never done by the EIFS applicator. More and more however, the burden is being placed on stucco applicators to completely seal the wall. Nobody likes asking for their cheque, then being told they’re expected to do more work that wasn’t included in their original scope and pricing. It’s perfectly reasonable to expect the applicators to take care of this step as part of their work — as long as it is clarified in advance so that they can include it in their price.
