How Much Can Lumber Shrink?
This has been one of the biggest problems in the
construction business for years. The bigger the piece of lumber, the
more it can shrink. There are large pieces of lumber that have been kiln
dried where most of the moisture has been removed and this wood seems to
remain the same size and rarely shrinks.
The reason why lumber shrinks is because, it's losing moisture. This moisture is from the original growth and can often create problems, if the lumber isn't dried out properly. The lumber yard is responsible for drying out the lumber so that it can be used effectively while building a home, but sometimes they're in a hurry and this lumber get shipped off shortly after it has been milled.
Now here's something that might shock you, I personally watched a 2 x 12 that measured 11 1/2" shrink to 11 1/8" in just two months. This happened in the middle of summer, in an extremely hot environment, but never the less, I witnessed this event personally.
I have also spent plenty of time building stairs and while working on large building tracks where homes numbered in the hundreds, watched my stair stringer’s shrink between 1/8 of an inch and 3/8 of an inch on a regular basis. This isn't uncommon and sometimes creates problems for home framers.
Generally, the smaller the lumber, the less shrinkage, in other words a 2 x 4 that measures 3.5" x 1.5" will rarely shrink more than 1/8 of an inch. The biggest problem with the smaller lumber however is the fact that it will twist and warp easier than a larger piece.
Don't be surprised if you're working in warmer climates, to see your lumber shrink. How much its shrinks is going to be entirely up to the piece of wood itself. Always keep lumber shrinkage in the back of your mind when framing or working with lumber. Sometimes these boards seem like they have a mind of their own.