Answers to commonly asked questions on FR shakes & shingles

By Richard E. Gardner Chairman of the Technical Committee Western Wood Preservers Institute

EECENT major fires in various Jlareas of the West have lead to new ordinances regulating the use of roofing materials.

The ordinances, as enacted, restrict or prohibit non-fire rated roofing materials on dwellings, and on commercial and public buildings, where not currently regulated under the local codes. Primarily, the ordinances are written to prohibit or control natural (untreated) wood shakes and shingles on dwellings. The ordinances generally apply to new roof construction, and reroofing when it exceeds a given percentage of the roof.

Pressure treated wood shakes (or shingles), tile roofing, asphalt shingles and other materials are fire rated Class A, Class B, or Class C according to their performance in standard fire tests. Class A rated roofing is the most resistant to fires: Class C least resistant. Untreated shakes, and shakes dipped or sprayed with fire retardants, do not meet minimum Class C and, therefore, have no fire rating. Pressure treated shakes can attain Class B ratings, but there are none with Class A ratings.

The nationally recognized standard for testing and rating roofing materials is Underwriters Laboratories, Inc. standard UL-790. UL-790 is the basis for UBC Standard 32-7 and ASTM Standard E-108. Producers of fire rated wood shakes attach labels to each bundle with information stating the fire rating, inspection agency, and standard(s) under which the ratings comply.This information is a necessity for building inspectors.

With restrictions now being applied to roof coverings on dwellings, many dealers are for the first time being asked about fire retardant wood shakes. The following are responses to a few of the questions that often arise.

Q: Do different roofing materials with the same fire rating have equal fire resistance?

A: Yes. Pressure treated wood shakes with a Class B rating have equal fire resistance to Class B asphalt, Class B synthetic shingles, or any other Class B roof covering. Treated wood shakes actually undergo tests in addition to the standard tests required of non-wood roof coverings, e.g., onlytreatedshakes are subjected to the flying brand test, and only treated shake test decks are exposed to outdoor weather and tested over a l0 year period.

Q:

A:

Do fire rated wood shake roofs meet requirements for one-hour or two-hour rated roofs?

No. UL-790 measures protection against fires that occur top-side on a roof. Time ratings are deter-

Story at a Glance

Consumerinterest in fire retar. dant wood shakes increasing . . . dealers must be able to field queries . . . experts give answers so retailers can re. spond to commonly asked questions.

mined by test method ASTM E-I19. E-l 19 measures the ability of roof structures to support roof coverings for a given time period. Ratings under UL-790 can not be correlated with ASTM standard E-l19. They are entirely different tests.

Q: Do fire rated wood shakes meet Class I flame spread requirements?

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