Wood and Weather after Final Dimensioning

[derek labian]

I'm not sure how it cupped because I didn't realize the issue until I started moving them around. 3 boards were very lightly cupped or twisted, maybe a 32nd of an inch. One board cupped heavily, 1/8 or more of an inch. I guess that would be one of Don's "unstable" boards. Maybe it's a bit of luck, if I had assembled with that board, the results would maybe not be so great. I purchased two more 8/4 boards with strait grain to replace that one. So far I'm not sure they have reverted at all, so I may just re-dimension them slightly smaller right before assembly and hope for best.

[Don Stephan]

Bruce Hoadley covers this in detail, working through an example of moving wood from one ambient himidity level to a different one.

Wood expands and contracts at a different rate along the growth rings than across them. Hence flat sawn boards may show cupping or flattening out with hunidity changes. Quarter sawn wood should not cup with humidity changes. But it will get wider or narrower to some extent. All depends on the amount of humidity change in the ambient air.

I don't believe any finish completely blocks moisture movement, but most if not all will show the rate of moisture movement. This may be the reason it is always recommended to apply the same finish to all surfaces, so the rate of moisture movement is similarly decreased.

Every few months I have to re-read portions of Understanding Wood but it is an excellent reference book for any woodworker. A similar book is Cut & Dried​ by Richard Jones.

[Tom Bender]

A solid wood door might not be a good choice as an exterior door in Houston, especially if it gets wet.

[derek labian]

Partially I think it depends on whether what you’re seeing is from the weather changes or if it’s more because there were stresses in the wood (either from the tree or b/c it was dried too quickly) that shifted the wood a little after it was cut. Doesn’t hurt to try to clamp it with higher humidity but I wouldn’t bet a lot of money on it.

Too late now, but as someone who also goes a week (or longer) between steps in a project, I try to rough dimension everything in one session and leave the final dimensioning to be done the same day I’m doing assembly.

Yeah, a good lesson for future projects.

These doors have 48 parts that have to be final dimensioned.. so it takes a substantial amount of time to final dimension before a glue-up. In any event, I bought two more pieces of 8/4 and I think the project will be fine. The biggest challenge will blue gluing everything up before it sets.

The final result of my attempts to un-cup and twist the wood were failure. No meaningful difference.