Q&A Spotlight: Timber Frame Wood Choices—What Works, What Doesn’t, and Why – GreenBuildingAdvisor

Q&A Spotlight

A discussion on wood species, moisture, and detailing for long-lasting outdoor timber-frame structures

Any time a builder can use locally sourced materials, it’s a win—right? Lower cost (hopefully), less transportation, and support for the local economy all check the right boxes. That’s what “Agoldstein” was thinking when asking about an upcoming project.

Their client wants a carport timber-framed with white pine. This species choice, while perfectly adequate for protected interior work, is not known for its durability in the elements. Goldstein writes, “I would like to use a redwood or locust but there isn’t money in the budget for that. Has anyone had experience using green, white pine to timber-frame, or could anyone recommend another budget-friendly species that’s more naturally decay resistant?” He goes on to refer to the International Building Code (IBC 2304.12.2.2 ), which states that posts or columns must be “naturally durable,” not exposed to weather, tied to a concrete pier, and not placed within 8 in. of exposed soil. He writes that he plans to use tall sonotube footings and galvanized post brackets; combined with the roof above, the white pine should be code compliant. “But I also want the structure to last.”

The topic for this Spotlight: What’s the best wood species for an exposed timber frame?

Methods for dealing with pine

In addition to pine’s susceptibility to rot, Goldstein will have to deal with the issue of green lumber. Expert “Peter Engle” thinks that even well-protected pine will rot outside but advises that Goldstein consider using a penetrating treatment to seal the timber’s end grain and do everything to keep water away from the post bases. Engle also cautions that green timber joinery will move as the wood dries: “Best practice is to air dry it to less than 20% MC before doing your joinery.” Engle goes on to suggest storing the material under…