Inspect Your Scuppers

Scuppers are those small openings in exterior walls that allow water from roofs or decks to drain off through a guard wall or parapet. In multifamily residential construction, they are usually made of small sections of sheet metal tubing, like "drain pipe", four to six inches across, and three to four inches high. They usually protrude from a stucco or wood balcony wall, or roof parapet wall, for about three inches. While their purpose is to drain water to the outside, the way they are typically installed actually allows water to drain INTO construction. This ironic turn about in multifamily construction causes homeowner associations to unnecessarily spend a great deal of money in premature repair of roofs, decks, rotted wood framing, and other components.¹

Buildings stay dry because their interior space is protected from the exterior elements by a barrier separating inside from outside. The building code refers to this barrier as the "weather resistive barrier." Scuppers are actually openings in this weather resistive barrier. Their intended purpose is to serve as a conduit through this weather resistive barrier for rainwater to pass from a roof or deck to the outside of the wall where it can continue on its path to the sea. While most scuppers function successfully in this manner, nearly all scuppers in residential and condominium construction also serve as a conduit for water to get back into the interior, by traveling back along the outer surface of the sheet metal tube,where it passes through the weather resistive barrier. This is possible because the metal tube is not sealed nor flashed against the passage of water from the outside back into the wall. (Caulking the joint between the scupper and the stucco or wood that surrounds it is not an effective seal.) Water also can travel back into the wall along the bottom of the scupper, similar to what happens when a partially filled drinking glass is slowly tipped on its side.

To be installed correctly, scuppers should be installed like little windows, with flanges all around, properly flashed so water cannot travel back behind the weather barrier using the scupper itself as a conduit. Unfortunately, this requires more time and effort than the usual installation, and is therefore almost never done. The installation of scuppers in construction without flanges flashed into the weather resistive barrier "shingle fashion" or, "weatherboard fashion" is a defect in construction.

Inspection Recommended

Homeowners, directors, and property managers can eliminate or reduce damage to their property from improperly installed scuppers by inspecting their installations and taking appropriate preventive measures. Check around the scupper as it protrudes from the wall. Often there are openings of 1/4" to 1/2" between the stucco or wood and the scupper. This is where the water gets in. Sometimes the space is tightly closed, with the stucco snug against the sheet metal. No matter; even a hairline crack between the two lets water in.

Preventive measures include the injection of fungicide preservative into the space around the scupper, where water was likely gaining entry. A borate-based preservative such as Bora-Care is best because the borates kill any fungus presently growing in the wood framing and remain "on the job" for many years to come to eliminate any new fungus from taking up residence.

Retrofit Possibilities

A good retrofit of a defective scupper is to remove the stucco, brick, or siding around the scupper for about 6" all around and fit a sheet metal rain collar over the scupper. The rain collar should have a 3" flange on the top and on both sides, similar to the nailing flanges of a window with the corners soldered, and a section to completely cover the scupper top and both sides. It should be installed against the weather resistive barrier with its flanges properly shingled into the weather-resistive barrier as in the fashion of windows.

Although the proper correction requires the fitting of a flanged collar against the weather barrier, a less effective, less costly alternative is to fit the scupper instead with a collar that can be sealed against the outside of the wall and the scupper itself, to prohibit the further entry of any water. The seal should not be an inexpensive caulking application but should be a permanent sealant with a properly formed and prepared joint.

Finally, the scupper discharge itself must be modified to incorporate a "drip," a down turned lip at the lower outside end of the tube. This will eliminate the possibility of water passing through the scupper from running back into the wall along the bottom of the tube itself.

If the entire scupper is not to be uncovered to the weather-resistive barrier and properly retrofitted with a rain collar shingled into the weather-resistive barrier, then the entire wall immediately above the scupper must be sealed against any water penetration to the outer surface of the weather-resistive barrier. Otherwise any water that penetrates the outer skin of siding, brick, or stucco and is caught by the weather-resistive barrier above the scupper, will drain down the outer surface of the barrier to the top of the scupper, where the water can then back-flow into the construction along the upper surface of the scupper.

Simply sealing the opening without killing growing fungus at the site is only the illusion of a repair. Existing fungus already inside the deck, roof, or wall framing will continue to thrive, consuming the wood structural components (dry rot) even if the source of the water entry is closed off. That's why a fungicide has to be applied first.

With a simple inspection and some low cost maintenance, costly major repairs to roofs and decks caused by defective scupper penetrations can be forestalled virtually indefinitely.²

¹Construction Defect Claim and Litigation (Aspen Publishers, Inc. 1995).

²Lee R. Connell, Jr., AIA, Condo Management, California, November 1995.

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