Model house frame units (two studs, top and bottom plates and a central “dwang”) were constructed using short (500-600 mm) lengths of framing timber. Constructed frames were impregnated with water using a mild pressure schedule to raise the initial moisture content to 35-40 % mc. The back face of each unit was then covered with black polyethylene. Two locations at the stud/dwang and stud/bottom plate interfaces were swabbed with alcohol and a 35 x 70 x 7 mm “feeder strip”, pre-decayed in the laboratory by brown rot fungi, were tacked in place on the swabbed area. Blocks of pre-wetted fibreglass insulation were then placed in the wall cavity and the remaining face covered with a layer of building paper and fibre cement board. Sets of units were stored outdoors from winter to early summer with replicate sets being stored in the Forest Research Fungus Cellar, maintained at 27°C and 90% RH. Units were lightly sprayed with water twice a week in order to maintain wood moisture content at levels suitable for decay. As expected, decay in units stored outdoors progressed more slowly than in those stored in a warm environment. At 24 weeks, untreated units were severely decayed, while those treated with a boron-based preservative were virtually free of decay. Units treated with a LOSP formulation containing permethrin had little resistance to decay but there was only limited decay in units treated with permethrin amended with 3-iodo-2-propynyl butyl carbamate (IPBC).

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