Difficult Details #1: Scuppers
A significant part of my consulting business involves reviewing the construction details for EIFS projects before the buildings are constructed. Often, an architect or owner will send me the plans and want me to comment on what he or she is thinking of doing. It’s money well spent, because few architects I’ve met understand EIFS well enough to properly design all the details on an EIFS building.
Typically, the architect’s drawings show basic EIFS details (some of which are often not completely shown on the drawings). Often, the “unshown” are the oddball or difficult ones for which little precedence is available in terms of standard industry details.
One of these most difficult and leak-prone EIFS details is scuppers. Scuppers are a type of true-wall penetration that functions as a drain for water. Usually this is for rain water, but it can also serve for water occurring by hosing off a deck or roof. Often, scuppers go through the wall of a deck that has EIFS on both sides, or through a parapet, which has EIFS on both sides. This article will provide you with some insight how to properly handle this common detail. You can keep this list and use it as a reminder when designing or bidding EIFS projects.
Scupper timeScuppers in EIFS walls are very difficult to seal because the wall is often hollow (made of studs and sheathing), and it is difficult to “marry” the complex scupper flashings into the EIFS coatings. Hence, if the scupper leaks, it gets into the EIFS wall construction, and may also get into the soffit below (if there is one). This can create havoc, as often decks on multi-unit condos or apartments are stacked-up for many stories, and if one leaks, well ... the rest will follow.
I’ve seen some “joke” details where a hole was drilled through the whole EIFS with a hole saw (after the EIFS was in place), then a piece of PVC pipe has rammed through the hole and caulked like mad. This kind of detail is cheapness taken to the extreme; it will work until the check clears. This detail looks awful and leaks after the first big rain. Here are some guidelines for doing it right.
Often scuppers are used as overflow protection. In other words, some sort of primary deck or roof drain, which is bonded into the horizontal surface of the deck or roof, is used to carry off water under normal circumstances. If this drain gets plugged, however, then the water is supposed to go out through the scupper. In order for this to work, the regular drain needs to be lower than the scupper and the water needs to drain toward the primary drain first, otherwise the scupper becomes the main drain.
Unfortunately, decks are often dead flat, and the water just sits there until there is enough so that it starts moving laterally. In the case of a flat deck, sometimes the water runs to the scuppers (or worse yet, under the frame of the sliding doors that lead to the deck) instead, bringing with it all the dirt on the deck or roof, and flushing it down onto the vertical EIFS wall below the scupper. This causes instant stains and looks terrible.
In order to function, the bottom-most part of the scupper needs to be flush or lightly below the surface of the deck. If it is not, the water will pond on the deck until it is deep enough to start flowing through the scupper.
Inboards and outboardsDecks almost always have some sort of waterproof coating on the top side. It is critical that the flashings that go through the EIFS go under the coating system. This must be done carefully, especially where the scupper flashing sheet metal turns upward at its edges.
The outboard end of the scupper needs to extend far enough past the outside face of the EIFS so that water running out the scupper does not get onto the EIFS. Water that gets onto the EIFS will cause stains, and often mildew. The outer edge of the scupper should have a drip edge (so that water does not flow back toward the EIFS wall), and the sheet metal should have a downward slope toward the outside, to ensure positive water flow.
On the inboard side of an EIFS deck of parapet wall, the EIFS should not be brought down to the roof surface. It should be terminated at least several inches above the deck or roof surface. The roof or deck membrane should be brought up behind the EIFS, and the bottom edge of the EIFS should be properly sealed.
Proper sealing depends on whether or not the EIFS is a barrier or drainage type, but in neither case should a raw foam edge occur. By terminating the EIFS above the roof or deck surface, the scupper flashing can be married into the roof membrane or deck coating (not the EIFS), creating a proper seal.
The outside portion of the scupper flashing is a different situation. Because the EIFS coatings are so thin, it is nearly impossible to incorporate the scupper flashing into the coatings. Instead, it is allowed to project through the EIFS, and is sealed with backwrapping and caulking.
Proper scuppers through EIFS requires some design ingenuity and careful craftsmanship. In addition, some coordination is required between the EIFS installer, the roof/deck membrane installer, the sheet metal man and the sealant installer.
In all, scuppers are a fussy type of detail, but it does need to be done properly. If you don’t believe me, then consider this: Most decks have scuppers, and often decks overhang each other. In this case, the water simply flows off the building and to the ground. But when decks are built over an occupied, indoor space, heaven help you if they leak and the space below is occupied by lawyers.