The lumber used in construction today is mostly new growth forestry, with much less dimensional stability than the harder old growth wood of the past. What this means is that today’s wood expands and contracts and twists significantly if moisture content of the wood varies. Because of this dimensional change in wood, we need flexible coatings. Newer technology coatings are micro-porous, allowing breathability.

Older technology products like oil based paints and primers, and spar varnish all continually harden as they age. Eventually these hardened coatings become brittle, and if wood expands, it cracks the coating, allowing moisture intrusion, and further expansion and contractions of the wood.

Bottom line, change is hard, and change costs money. For the window and door manufacturers to change to superior performing, flexible, breathable primer and coating systems, they would increase production time by slowing the dry time. Until customers demand an end to rotten wood on homes, they will continue to use old outdated technology like factory application of hard oil based primer.

Our products of choice for most exterior wood is a field applied acrylic house paint primer to bare wood,( two coats if bleeding type wood), followed by 2 coats of premium acrylic house paint. We strongly discourage the use of factory primed wood products for exterior service.

With respect to natural or clear finishes on exterior wood, we like Sikkens Woodcare Products , which are flexible, breathable coatings, utilizing trans oxide pigments giving superior UV protection with approximately 36 mo maintenance cycles. Most Sikkens products are solvent based, but through advanced technology, still have the flexibility required for exterior wood protection. Some newer water-based products are good choices as well. Typically the water-based wood sealers we have evaluated seem somewhat “muddy,” and require more frequent maintenance. We do, however believe the water based natural finishes are a good choice with respect to environmental issues and safety.