Fire-Retardant Cedar Roof
Keeping the fire-retardant shakes in great shape
I'm reroofing with red cedar shakes treated with a fire
retardant. They have a class C fire rating, the minimum required by
state law. We'd like to keep them looking light and new as long as
possible. But mostly we just want to preserve them and maintain their
fire resistance. Any suggestions?
— Raymond, San Jose, CA
Tom Silva replies: Just one: Forget about keeping your roof looking like new; wood is going to turn gray no matter what you do. As for fire resistance, do not apply any coating that claims to be a fire retardant. Shingles that are certified as fire-retardant will be permanently
protected from fire. As for preserving them, the main thing is to keep
the roof clean. An annual sweeping (or blowing) removes pine needles,
leaves, and other debris that can accumulate on the roof and trap water
against the wood. Pruning overhanging tree branches will help reduce the
debris and discourage the growth of moss, another surefire killer of
wood roofs. There are any number of products that claim to prolong the
life of a cedar roof, and little agreement about their effectiveness.
Even the Cedar Shingle & Shake Bureau doesn't come right out and
recommend anything. It simply suggests that if you're going to put them on, you should at least enlist the services of a reputable contractor
with a solid record locally. According to the bureau, the most suitable
products will be formulated specifically for wood roofs, and contain a UV inhibitor, a water repellent, and/or an EPA-registered wood preservative. Before you apply anything, check with the company that made your shakes to be sure it's compatible with the fire retardant.