When using H3.1 treated timber externally (cladding, facings, fascias, and the like), NZS 3602:2003 Timber and wood-based products for use in building clause 111.22 requires that, to meet durability requirements:
- the timber must be primed and painted with a minimum of two coats of acrylic or alkyd paint
- all cut ends, notches, holes, and other exposed surfaces must be primed on all faces.
Manufacturers of these products have their own data sheets that outline the requirements for:
- the protection of the product during delivery to and storage on site – they must be kept dry before being installed
- the maximum time the primed timber can be exposed to the weather before repriming is required – where the exposure time is exceeded, the timber must be sanded and reprimed
- suitable coating systems.
Further guidance is contained in AS/NZS 2311:2009 Guide to the painting of buildings clause 3.2.8 and Table 5.2.
Summarised from BRANZ GUIDELINE Newsletter, October 2014.