Preserving a shake roof needs expertise

Q. My 12-year-old wood shingle roof has had some of its ridge shingles replaced. The roofter told me that the roof might last for another four years even though the shingles appear to be in good shape to me. Is there a sealer or preservative which I can apply by brush or spray to make the shingles last longer? P. H. Carstulovich Stockton, Calif.

A. If top-grade wood shingles or shakes were applied according to the manufacturer's specifications, and if the roof is of sufficient pitch, there should be no need for a field application, brushed or sprayed. A lot depends on the climate, whether dry or damp.

Sometimes such practices reduce the life of the shingles, especially if applied by an amateur who uses improper methods or materials.

The ideal recommended preservatives are factory applied at the mill before the shingle bundles are delivered. However, veteran roofers have successfully used, at 10- to 15-year intervals, a mix of five gallons of raw linseed oil with three pounds of graphite.One California roofing family has been using this formula for at least a century.

The REd Cedar Shingle and Hand-Split Shake Bureau generally has looked with a jaundiced eye on field applications of wood preservatives on shingles and shakes , but this again depends on the climate. Still, the bureau has relented somewhat, especially in regard to fungicides in very damp climates.

The subject is sufficiently controversial to recommend a letter from you to the bureau. Address you letter to the Red Cedar Shingle and Hand-Split Shake Bureau, Suite 275, 515 116th Avenue, N.E., Bellevue, Wash. 98004.

Describe your particular roof, shingle grade, unit exposure to the weather, roof pitch and age, local climate, quality of application, and present condition. Then follow the bureau's expert recommendations.

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