Synthetic Stucco Leakage

Kendall Holmes

"I've read some news reports about leakage problems with synthetic stucco siding. My house is eight years old and we've never had any problems--at least, none that I know of. Should I be concerned?"

You should be if you want your new house to become old someday!

Indeed, the National Association of Home Builders now warns that even when it is properly installed, synthetic stucco (also known as EIFS) can develop rot-causing moisture intrusion problems.

And building materials manufacturer USG--a major manufacturer of synthetic stucco in earlier years--has created a separate web site to warn homeowners about the dangers of the synthetic stucco used widely in the 1980s and 1990s around the country.

On the site, USG warns that synthetic stucco synthetic stucco system it used to make (and others still make) is "neither practical nor reliable." Further, the company quotes a researcher as warning that every house clad with synthetic stucco will eventually suffer problems from water leaks, and their resulting damage.

To me, that's pretty scary!

To understand the problem it helps to take a look at how synthetic stucco differs from other types of siding that are used to cover wood frame houses--such as vinyl siding, clapboards and bricks. While each of these systems is designed to repel water, each offers a way for water to drain out when it does get behind the siding. With clapboards, for example, water can drip out at the base of each row of siding.

Now let's look at how synthetic stucco or EIFS (for Exterior Insulation and Finish Systems) is applied to a house. First, rigid insulation board is glued firmly to a home's frame or sheathing with adhesive. Then this insulating board is covered with fiberglass mesh and two layers of a hard synthetic finish.

It is this synthetic finish layer that resists water. What EIFS systems lack is a harmless path of escape for water that does happen to penetrate this outer layer. And that's where the problem lies. In the real world, it seems, water always gets behind siding.

"There is definitely a problem with the barrier concept," says Jim Reicherts, a USG product manager, in a company press release. "It's pretty hard to ignore the fact that moisture intrusion does occur on barrier systems.

"Whether that intrusion occurs because of defects within the system itself, faulty sealants around windows, poor window construction or improper maintenance, the end result is the same. No matter where or how water enters behind a barrier EIF system, there's no way for it to get out. It remains trapped inside the system, where it can eventually damage and rot framing, sheathing, windows and other moisture-sensitive building components."

In response to these problems, EIFS manufacturers are now developing systems that allow water to drain to the outside. Of course, this doesn't help the owners of the hundreds of thousands of homes built in the past decade with barrier EIFS systems.

What should you do if your home is clad with EIFS?

    • The NAHB urges homeowners to get their homes checked at least yearly by a professional experienced in EIFS water intrusion inspections.
    • It further urges homeowners to immediately tackle any repairs that may be needed--as delays can cause minor problems to escalate into major problems that will cost tens of thousands of dollars to fix.
    • And like others who have studied the EIFS problem, the homebuilders' association suggests that many homeowners may want to have their house re-sided with something else.

Synthetic stucco seemed like a great idea to many homeowners and builders. Now it's becoming a recurring nightmare.

About the Author
By Kendall Holmes, The Old House Web

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