Exterior weathering trials on radiata pine roofing shingles
D V Plackett, C M Chittenden, A F Preston
A series of test roofs clad with radiata pine (Pinus radiata D. Don) shingles that had been pressure-treated with various water-borne preservative formulations were installed at a Forest Research Institute test site in Rotorua in 1977. A further series of test roofs installed in 1978 included radiata pine shingles pressure-treated with a commercial light organic solvent preservative (LOSP). Evaluation of selected radiata pine shingle test roofs in early 1984 showed that, although preservative leaching had occurred from shingles treated with an alkyl ammonium compound (AAC), a copper-chrome-arsenic (CCA) preservative, and an LOSP, the shingles appeared sound when examined microscopically. Slight lichen growth was evident on some shingles. In contrast, untreated radiata pine shingles displayed marked fungal infection, early stages of decay, and plentiful mould and lichen growth. Western red cedar (Thuja plicata D. Don) shingles, which were used as a reference point from which to judge radiata pine shingles, showed lichen and mould growth after seven years' exposure. Checking and cupping of western red cedar shingles were attributable in part to the inclusion of some flat-sawn material.