Can cement stucco and EIFS work in wet climates? The answer is yes and we can prove it. A recent study from the NAHB Research Center reported that brick veneer was the most dry of all claddings they tested. They really need to know all the facts.
First, EIFS was omitted from the test, which in my mind was a good thing. Not because EIFS is bad but the test they performed was bogus. Second, the test was sponsored (paid for) by the Brick Industry Association and the EIFS and brick industries have been fighting each other for years.
The test was performed on eight wall assemblies with wood framing and various “selected” claddings over them. As reported, each wall was exposed to the weather for a year. Here is the kicker: Each wall was constructed so a portion of the water-resistant paper was “compromised” and water was poured behind the cladding. I could have predicted the results before they even started the test.
The brick veneer, the only cladding with a 1-inch clear cavity, won. The water flowed down the back side of the brick, never touching the building paper on the sheathing. If you think this proves that brick is better, you can put the same airspace on any cladding (we call it rainscreen). Now, if they would have tested brick veneer with a 1-inch airspace against similar wall assemblies that would be fair. The test was, in my opinion and from what I’ve read, 100 percent rigged and pointless.
I will not trash brick as a cladding. It is a good cladding and a historic material but let’s be fair and honest about testing. Good construction means dry walls and bad construction means trouble, regardless whether it is brick, EIFS, wood siding or stucco cladding. A clear airspace certainly affords for some poor construction practices, but it does add cost. How about building it right from the start? Using qualified contractors, good details and traditional systems will keep walls dry at a reasonable cost.
If you are into reports and must have one to back up your design choice, how about the ASTM STP 1269 on the life-cycling cost of EIFS and other claddings? EIFS, brick and stucco were all compared using good design and construction practices. The winner was stucco with EIFS coming in a very close second place for life-cycle costing of cladding for a commercial building. Of course, they all have to be assembled within industry and code standards. So, I guess if you plan to build it correctly, use EIFS or stucco. If you plan to construct the wall incorrectly, we encourage you to stay away from stucco and EIFS.
But stucco in a wet climate?
I was asked to visit a five-story condominium with cement stucco cladding installed over two layers of Grade D paper. The building sat on a hill in Seattle. The mid-rise stucco building with no overhangs was exposed to the Pacific Northwest’s famously nasty, wet weather for more than 10 years. An earthquake rattled the building and while the stucco developed a few hairline cracks, which were no issue, so did the window frames and they started leaking into the cavity of the wall.
It was decided that the windows had to be replaced and that removal of all the stucco was basically the same cost as patching around all the windows. When I arrived back at the site, the stucco had been removed. The 10-year-old wood-based sheathing under the stucco looked like new. The lesson learned was good design, with good flashings and a good contractor to install them, works. The architect who designed and detailed this cladding used basic flashings but required all penetrations to be walked and thoroughly inspected prior to plastering. He also set qualifications for the plastering contractors who bid the work in his specifications. He knew that a low price was just not worth it in the long run.