Getting some Painting Done?
When painting any bare timber surface, the Australian Standard AS/NZS 2311:2017 Guide to the Painting of Buildings specifies 1 coat of a quality acrylic or oil-based primer be applied, followed by 2 coats of a quality acrylic or oil-based topcoat.
Some topcoats for exterior timber surfaces are self-priming (e.g. Dulux Weathershield) and are suitable to use as a 3 coat system, but using a quality primer as the first coat is considered best practice for evening porosity, and blocking tannins and stains. Self-priming paints are not a 2 coat system, 3 coats must still be applied.
Unpainted rough sawn timber boards will use 30-40% more paint than face dressed (smooth) board.
Lately, I have encountered poor painting application to Pre-Primed Timber Weatherboards which are factory-coated with a thin, holding primer that is only designed to provide temporary protection during the construction process. This primer is generally not considered to be part of the paint system and should be sanded and coated in an appropriate prep-coat, followed by two finished coats, or 3 full coats of Self-Priming exterior paint.
It is also important to remember that Manufactures Installation Guides play a vital role in highlighting the standard and material application required to achieve building compliance. Especially with paint materials, these guides and PDS are readily available.
Section 12.02 of the Guide to Standards & Tolerances (2015) states, “Paintwork is defective if the application has blemishes such as paint runs, paint sags, wrinkling, dust, bare or starved painted areas, colour variations, surface cracks, irregular and coarse brush marks, sanding marks, blistering, non-uniformity of gloss level and other irregularities in the surface that are visible from a normal viewing position. Paintwork is also defective if the application results in excessive over-painting of fittings, trims, skirtings, architraves, glazing and other finished edges.”
Lastly, beware of cheap gap fillers. A quality gap filler with a highly elastic compound or high percentage flexibility rating will be able to withstand general building movement, especially at junctions of dissimilar materials. Any cracking at the handover of a building or painting project is considered defective. Often this cracking is simply a result of the type of gap filler used.