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A Close Look at Stucco

A Close Look at Stucco

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    Flashing details frequently involve the interaction of two trades. Here, for example, the stucco crew members responsible for installing the building paper had to remove and reinsert a gable vent installed by the framers so that they could run building paper under the vent flange.

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    Integrating building papers with window flashings can be a challenge on site. In California, where this crew works, stucco contractors aren't typically licensed to install windows, so the paper crew must work with the existing flashing. Here, the window crew left the window perimeter protected by strips of flashing, with side strips lapped over the bottom strip and the head strip lapped over the side strips and the window flange. The paper installer lifts the bottom flap and runs paper under it.

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    The installer seals the flashing to the paper with adhesive membrane.

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    He lays paper under the side window flashings and staples the flashing down before applying membrane to this joint as well.

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    Paper-backed lath then butts directly to the window flange, but water that gets behind the stucco at the window sill and jamb will be handled by the membrane, the flashing, and the first layer of paper.

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    Less than ten years old, this building had been repaired twice previously with surface-sealing methods that did not work. The author's crew first stripped the stucco. At this window corner, badly detailed flashing and paper let water soak the sheathing and framing, leading to rot.

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    After pulling out the window, the author's crew repapered the wall with Tyvek StuccoWrap, then applied membrane and Tyvek FlexWrap to the rough sill to protect the wood structure even if the window leaks.

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    The crew then replaced the window.

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    The crew slid the top flange under the Tyvek and sealed the flange to the Tyvek all around the window.

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    The crew applied a second protective layer of Grade D building paper.

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    Roof-to-wall intersections create particular problems. This bad detail held up the work: The rafter placed tight to the building wall does not allow paper to slip behind it, and the flashing left by the roofers will direct water behind the stucco and into the wall if used as configured.

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    A water diverter (kick flashing) was installed by the author's crew in a retrofit job: This design will lead water out away from the wall and dump it off the roof's drip-edge rather than into the wall. Papers installed on the main wall can readily integrate with the membrane and flashing between roof and wall at the rafter tail.

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    A wall-and-roof intersection built without the correct flashing detail shows discoloration and staining after a few years in service; the author typically finds significant rot in buildings with this detail, even though the wall surfaces may show only minor traces of trouble.

Roof-to-wall joints. The most damaging leakage we see in our work takes place where roofs intersect walls, either because a one-story roof meets a two-story wall, or because a chimney chase meets the roof. It takes work to keep the roofers and the stucco applicators coordinated so that their work interweaves correctly.

Every roof needs some kind of L-shaped flashing where the roof abuts the wall. Metal step flashing, or as we call it, "step shingles," is typical for asphalt or shake roofs; tile roofs usually get a continuous piece of metal J flashing.

Where stucco is new in the market, the appropriate metal step shingles for stucco application can be hard to find. Folded flashings intended for use with asphalt shingles and vinyl siding are too small for stucco. In Salt Lake City, the typical step shingles on the shelf are 8 inches long, with a 2-inch leg for the wall and a 4-inch leg for the roof. Stucco requires a 2-inch reveal between the bottom termination of the stucco and the roof surface (many EIF systems need a 3-inch reveal), and a 2-inch lap of the building paper over the metal, so step flashings must have at least a 4-inch vertical leg.

Since you can't be sure of finding the right size metal flashings in all markets, I always use rubberized asphalt sheet material like Ice and Water Shield as a backup.

However, the flashings are still important, particularly the water diverter or "kickout flashing" at the bottom of the roof, which kicks roof runoff away from the wall system. Where this is not installed, water from the roof will overwhelm the stucco system and cause at least a visual problem, and commonly a major structural problem.

Penetrations. Every penetration in the stucco — hose bibb, dryer vent, combustion air intake, or whatever — is a potential leakage point. Our solution for those spots is to use bent and soldered metal to make up a set of standard shrouds, like the hoods that cover dryer vents, in various sizes to meet the most common needs. We caulk the back side of the shroud to the paper below it, and caulk the paper above it to the shroud's top and side flanges. Then we terminate the stucco at a casing bead.

Homeowners Pay the Price

In Salt Lake City, my stucco repair business is thriving. We also have a lot of work fixing homes with EIFS and cultured stone exteriors — the underlying drainage-plane problems are the same.

Recently, I started a company, Ram Exteriors, to install hard-coat stucco on new homes. But I'm thinking of shutting it down. We haven't been able to get much business, and we have barely broken even on the jobs we have sold. The cut-rate competition is just too tough. It's ironic, but I can find plenty of work fixing bad stucco at four times the cost, and very little work applying stucco right in the first place.

The consequences are tragic for homeowners who don't understand the issues. I was called to do an estimate on one house up for sale, where the buyer had hired a home inspector from back East and the inspector had flagged the stucco system. I told the buyers they were looking at a system that was trying to drain water on the exterior and lacked the right flashings and papers under the cladding. Even if we found no structural damage, I told them, it would be at least $30,000 to retrofit the home to provide good drainage details.

That buyer backed out of the sale. But I heard that the house sold weeks later to another buyer who did not have a home inspection done. Someone has bought the trouble.

I worked for another couple who bought their home before they saw any problem. They called me because of leaks and musty odors. When my crew started to open the walls, the foreman called me from the site and said, "You better get over here, Dennis. This house is about to fall down." When I got there, sure enough — the home's framing was almost gone. There was a risk of imminent collapse.

Utah has some of the weakest liability laws in the U.S. That couple's lawyer advised them to settle for $50,000. In other states, the builder would have been on the hook for the whole value of the house. If the builder's insured, that's a hit he can handle — once, and then lose his coverage. But I know some contractors who have thought they were covered and never were: Exclusions they hadn't read in their insurance policies ruled stucco out, and they didn't even know it.

Whether your insurance covers you for stucco failure or not, that isn't a road you need to go down. The way to prevent the human cost isn't with insurance. Insurance is for unavoidable disasters, one-time deals. If stucco is done wrong, failure is predictable: You can expect it. And the way to avoid stucco failure is simple: Provide the system of flashings and papers that will keep water away from the wood. If you do, you'll have something better than insurance: a weather-resistant home exterior that does its job.

Lifelong contractor Dennis McCoyowns and operates Ram Builders, Inc. (www.rambuilders.com), based in Lindon, Utah, with operations in Utah, Texas, and California.