Wood and water together can spell trouble. Lengthy exposure to moisture or extreme fluctuations in moisture levels can cause problems with wood, like checking, warping, paint failure, and even rot.
Proper building design and construction can help mitigate these problems. Well-known practices to prevent moisture accumulation within exterior siding include:
• Using dry materials during construction
• Providing adequate clearance to grade and drainage at grade
• Designing with adequate roof overhang
• Installing appropriate flashing materials
• Installing an interior vapor retarder in cold climates.
In a recently updated FinishLine fact sheet, another less-used but fairly simple technique is explained: ventilating horizontal lap siding by installing furring strips between the sheathing and siding. The fact sheet discusses materials and methods of installation in detail.
Although most of the article focuses on moisture, perhaps the most important factor impacting the service life of paint on exterior wood is also covered: exposure to sunlight.
Tests of wood painted, or at least primed, before any exposure to sunlight showed that repainting was not necessary for at least 30 years. Wood exposed to two weeks of sun prior to priming required repainting at 10 years. Applying a layer of primer immediately to wood siding will likely save time, effort, and expense years down the road.