Repairing moss-covered cedar-shake roof

Q. The 15-year-old cedar-shake roof on my house, located in a wooded area, is growing moss, thus causing the wood to rot. How can I get rid of the moss and treat the shakes to fend off further moss growth? Benjamin O. Schwendener Jr. Okemos, Mich.

A. Moss grows in the shade and where humidity and moisture abound. By contrast, wood shakes or shingles on sunny, well-ventilated roofs are generally moss free.

Most homeowners balk at cutting down adjacent trees to let in a little sunshine. Trimming any nearby trees is generally more acceptable as a starter to solve the roof-moss problem.

First, you have to manually remove the moss. Avoid wire brushes since they may harm the shakes. Use bristle brushes or blunt scrapers instead.

Follow with a fungicide treatment. Dow Chemical, Monsanto, and Sherwin Williams make commercial moss deterrents. Check your local paint store. Follow the labeled directions.

One homemade fungicide is mineral spirits mixed with 10 percent pentachlorophenol (penta). Apply liberally to the scraped or brushed shakes.

Depending on the extent of the shake rot, remove and replace any bad ones; or in the extremity, install a new shake roof. At the same time, remove and replace any damaged roof sheathing under the shake roof.

An annual scraping and fungicidal treatment may be necessary and certainly advisable.

For more information get in touch with the Red Cedar Shingle & Handsplit Shake Bureau, Suite 275, 515 116th Avenue, NE, Bellevue, Wash. 98004. The telephone number is (206) 453-1323.