Comment on 2x2 lumber at Home Depot is now 1.28x1.28. Nominal size is supposed to be 1.5
SchmidtGenetics@lemmy.world 7 months agoHow does that work when wood varies due to moisture content? If they give precise mm measurements, only 20% of boards will meet those criteria.
Maybe they mill, store, and sell under the same moisture conditions?
Also, how big is the difference in size and moisture for the same piece of wood? I would expect that moisture is usually not higher than 90% and not lower than 10% or something like that, but don’t know how it really is
Once it leaves the mill they go to various stores and regions with different conditions.
Once I buy it at the store and take it the site, it’s now different from the store. You should acclimate all lumber for 48 hours before using it as well, this is so the wood doesn’t swell to shrink more after installing it.
A yellow pine 2x10 might move a tenth of an inch, not a full inch.
These were bought at the same time and are both 2x10 installed a couple days ago.
Over 3/8 of an inch and they both still need to dry.
So, more than 10% difference, that’s enough to be a problem, indeed
captain_aggravated@sh.itjust.works 7 months ago
Construction lumber, especially pressure treated lumber, is sold so wet I don’t think it really matters. I’ve actually never tried to calculate wood movement for construction lumber because who the fuck cares? But for furniture lumber which is dried to between 6 and 14% moisture, there is a formula:
width of the board in inches x percentage of moisture change * expansion coefficient for a particular species.
Yellow pine (extremely common construction lumber) has an expansion coefficient of .00263. A 2x4 (actual dimension 1.5" by 3.5") that undergoes a 4% moisture content change will grow/shrink 3.54.00263 = 0.03682 inches, or just over 1/32". That’s in width; it’ll vary by less than half that in thickness. Wood basically doesn’t move along the grain; the board won’t get appreciably longer or shorter.