Cedar Shakes

Asked August 28, 2014, 6:44 PM EDT

I have a cedar shake roof and am told I need to periodically treat it. I keep hearing about copper napthenate. Should I apply it and if I do at what concentration. Basically what should I use(if anything) on my roof. Thank-you Glen Butherus

Linn County Oregon

2 Responses

Hello Glen:

The US Forest Products Lab provides some guidance (see "Wood Shakes and Shingles for Roof Applications") on finishes for cedar shake roofs. In general, they recommend avoiding finishes like solid color stains or varnishes – anything that forms a film. As the wood wets-and-dries the film will crack and peel off. A semi-transparent stain or water-repellent preservative are best.

And yes, copper naphthenate is commonly recommended as a wood preservative. That's what I use at home to treat the ends of pressure treated lumber that I've cut. Home improvement stores carry products such as Jasco Termin-8 for which the active ingredient is copper naphthenate.

Thank-you very much, the information you provided has me on the right track. Glen