May 11, 2015
While internal timber surfaces are able to be readily & satisfactorily coated with a wide variety of paints, stains & oils, the performance of exterior finishes, particularly on timber surfaces exposed to the elements of UV light, heat, cold, water, dust & grit, is an entirely different matter.
Dark vs Light
External dark coloured timber projects that are subjected to full sun exposure during Queensland's hot summer months can lead to shrinkage & distortion issues. This can occur to either naturally dark timber (oiled or clear finished) or dark coloured stained or painted timber.
If you are painting timber cladding, fences, decks or furniture that are fully exposed to outdoor weather conditions go lighter instead of darker. Dark coloured surfaces in hot sun exposure can reach temperatures of exceeding 70 Degrees Celsius. This will result in the timber 'cooking' & drying out to under 8% moisture content. Shrinkage & shrinkage distortion can result, and even correctly seasoned timber, may end up with unacceptable appearances.
Darker colours absorbing more solar radiation than light colours will also deteriorate the finish of the timber rapidly. Light colours, particularly white, reflect the maximum amount of UV light possible & provide the best protection to both the timber & paint film.
Fig: Distortion in dark coloured timber exposed to full sun
These types of performance issues can be minimised by following Timber Queensland's recommendations, including the use of appropriate robust fixings, & light or pale coloured stains or paints
Resource: Timber Queensland