Unfortunately, there is no long-term solution to the hazard posed by an untreated wood shake or shingle roof other than replacing them with fire-resistant types. Beware of spray-on "fire-retardant" products for wood shake and shingle roofs. They may be beneficial in the short term, but their effectiveness will degrade over time with exposure to sunlight and rain. Wood shakes and shingles pressure-impregnated with an exterior-rated fire retardant may be allowed in some communities. Contact your fire marshal if you have questions about use of treated wood shakes and shingles.
If you have an untreated wood shake roof (or worn-out, cracked, or missing shingles of any type), replacing it should be a priority. This is because embers from far away (as far as a mile or more) can land on the roof surface and ignite the shakes. Class A roofing material (asphalt shingles, tile, metal, slate, and composite materials that resemble shake roofing) is your best bet for ignition resistance. However, heavier roof coverings like tile and slate may require some strengthening of the substructure (rafters and headers), which will add to the expense. If you have a Class B or Class C roof covering, then you can do certain inexpensive things. Most of these deal with managing the vegetation in the first 30 or so feet away from your home. Trees shouldn't overhang your roof, and vegetation should be well maintained and spaced so that fire has a hard time spreading to your home. You should also avoid storing or allowing combustible materials to collect under your deck or next to your home.
