In the face of a heightened wildfire risk fueled by record dry conditions this winter (see "Dry winter heightens California wildfire dangers" in the Washington Post), two California towns considered a fire marshal's proposal to ban new shake roofs. Similar bans have been in effect throughout the West (see "Homeowner Fights Town Rules On Roofing"). As reported in the The Almanac ("New shake roofs OK for now in Woodside and Portola Valley"), the town council meeting was a face-off between advocates for wood roofing and insurance company representatives.
Roofers and a representative from a roofing shake manufacturer argued that today's treated wood shakes are more fire-resistant and can achieve a Class A fire rating. "There are no reports of embers landing on a treated roof and having it catch on fire," Bill Hendricks, a spokesman for Chemco treated wood shakes is reported as saying. "(Flame on a shake) creates a char barrier that starves oxygen."
Fire ratings for roof coverings are either A, B, C or non-rated. The test places different size burning "brands" (pieces of wood stacked in layers) on the roof surface in front of a fan. A 12-inch by 12-inch brand is used to achieve a Class A fire rating.
Despite the Class A fire rating, insurance company representatives took a broader approach, looking at the history of homes with wood roofs in the hills above Woodside, Calif. They questioned the safety of the fire-treatment chemicals, and argued that there is no evidence how long a wood roof will stay fire-resistant, suggesting that under the intense Californian sun, wood roofs dry out over time and become more combustible. The council decided to table the proposal until more information was available to answer key questions, including: What are the chemicals used in the treatment? How much do they leach into the environment and drainage systems? How effective will the fire retardant be over a roof's life?
It is this last question that is critical to the wildfire risk. There was no dispute that existing wood roofs present a significant hazard, and the towns would seek incentives to encourage residents to replace these.