Rain-Screen Query

Mike Guertin's article (March/April 2007) on using a rain screen was great. I am managing some restoration work for a condo association, which may include re-siding two multi-unit buildings to remedy severe peeling, bubbling, and chipping paint on cedar clapboard siding. Currently, there is no air space between the clapboards and the underlayment, and the existing siding is not back-primed. It has absorbed enough water over the last 12 to 15 years to make the paint bubble and overflow with water. After the siding is torn off, we expect to have to replace some rotted OSB sheathing, which we found on a test wall. We are planning to use HomeSlicker behind the new siding as recommended by a consulting engineer, and we are considering using fiber-cement siding as well.

Do you have any recommendations for details on a clapboard installation that are different from the cedar shake siding you wrote about?

Eric Gribin Gribin Construction, LLC

Michael Guertin responds: I don't use HomeSlicker beneath clapboard. Personally, I don't like nailing lap siding over this drainage mat, because it bounces too much and makes it hard to hand-drive nails. I end up getting too many claps cracking. A simpler and more cost-effective method for creating a rain screen beneath clapboard is to apply vertical furring strips over each stud location and around penetrations. Similar flashing details can be used as noted in the article. I typically use 3/8-inch pressure-treated plywood for furring strips. First apply housewrap, then furring strips at stud locations, then clapboard. You don't have to break clap joints at studs, either — just install small blocks of plywood behind the joints as needed. Make sure you use fasteners long enough to penetrate through furring strips, sheathing, and into studs by 1 inch. For fiber-cement lap siding, I use the same furring method as clapboard. Yes, I recommend back-venting fiber cement — not so much for paint performance but to promote drainage and help the siding dry. Fiber-cement siding is a "reservoir" siding, just like wood, meaning it sucks up water and holds it for a while then releases it (dries out). The more opportunity you give fiber cement to dry front and back, the better the wall will stay dry.

Heads Up on Soffits

Thank you very much for the January/February 2007 copy of your magazine. It is very informative for anyone in the building business in any coastal area of the U.S.

I was especially interested in the article about securing soffits. It covered a number of areas that I have been telling our architects and clients about for years.

Patrick F. Coussens MCT Sheet Metal, Inc.