A few years ago I created an online calculator for predicting how much lumber will expand or contract based on its percent moisture content (MC). I personally use it quite a bit! The calculator requires a starting %MC and a final %MC in order to calculate how much wood movement will occur. Unfortunately, sometimes it can tricky to predict a final %MC based on where in the country the piece of furniture will live.

In order to help with deciding on a final %MC there are equations that one can use (the equations have been previously published link). In order to simplify the calculations, I created an online calculator which allows you to enter your ambient air temperature and the relative humidity; the calculator will provide the %EMC (equilibrium moisture content) from these values. You could, in theory, use a relative humidity and temperature that would represent the largest deviation based on where your piece of furniture will live.

So if you know your starting %MC via the use of a moisture meter, you could then use the EMC calculator to come up with a final %MC in order to calculate how much expansion or contraction the wood might incur.

If you have any questions please let me know below.

For me, my lumber adventures always start early on a Saturday (they close at noon).  The lumberyard I purchase from (The Hardwood Store in Gibsonville NC) is 30 miles away, so when I go I always make sure to get everything I need for a project to avoid another trip.

Bring Stuff:  Here’s a list of things that I bring with me to the lumberyard:

1. Chalk – this helps when measuring parts onto long boards.
2. Tape measure – I’ve forgotten to bring this in the past, but my lumberyard has loaners available.
3. Cheap handplane – To help see the figure in rough boards. This is something that I think am going to start bringing.  My lumberyard skip planes so this isn’t always necessary.
4. Cut/parts list – This is absolutely necessary unless you plan on over-buying for every thickness that you’ll need.

Picking: Here’s some helpful advice for picking through lumber.  First, let me say that not all lumberyards tolerate picking; some will jump on you.  The lumberyard I go to now (The Hardwood Store) is very tolerant of picking, but be courteous.  I don’t think it’s a good idea to get on the bad side of those that work at the lumberyard so you might want to leave the stack of lumber the way you found it.  Sometimes when I go to the lumberyard the stack of lumber in some bins will look heavily picked through.  All that you might find are the discarded boards from those before you – lots of sapwood, curved, or knotty.   When this happens I’ve found that if you ask politely they’ll bring out a fresh pallet of lumber if they have it available; just ask nicely.  My lumberyard never has a problem with this and the guys that work there are super nice.

Finding figure:  The lumberyard that I go to skip planes all of their lumber.  Skip planing is the process of lightly planing lumber in order to expose the figure; this also helps with grading lumber.  My lumberyard does this and I really like it.  It’s a great way to see what you’re getting.  All of the beauty as well as any sapwood and imperfections are exposed so there are no surprises after you start milling at home.  If your lumberyard doesn’t do this you can bring a cheap handplane or a scraper with you.  Just expose a little bit of the figure with your scraper or handplane, but don’t go nuts in case you don’t buy it (you might want to check if they are ok with this).

“The Hardwood Store” (Gibsonville NC)