July 13, 2014 in Features

Ask the Builder: Tree growth affects lumber quality

Tim Carter Tribune Content Agency
 

DEAR TIM: I was at the home center yesterday trying to get some rough lumber for a project. I spent a long time trying to get pieces that were straight. Most pieces were warped or twisted or had large bows to them. I remember years ago it was easy to find lots of straight lumber. Also, door and window frame lumber seems to rot out in just a few years. The house I grew up in never had wood rot issues. What’s going on and what, if anything, can a person do to minimize wood rot without buying treated lumber? – Leslie W., Tacoma

DEAR LESLIE: You’re not alone. Not only have I had to pick through stacks of lumber to try to find good pieces, but I also get complaints like yours on a routine basis from other frustrated homeowners.

About 35 years ago, I was working on the second home I purchased. I estimate the house was built just after 1900 in a suburb of Cincinnati. I had to cut a small section of an overlapping floor joist to accommodate a plumbing drain pipe.

When I retrieved the 10-inch wide by 2-inch thick piece of lumber and looked at it, I was astonished. There were countless growth rings. Because of the curvature of the growth rings, you could tell this floor joist had been cut from near the center of the tree. I counted 153 dark growth rings. My guess, based on the shape of the rings, is that the tree the joist was cut from was 400 or more years old when it was felled.

Many people don’t realize that trees are a crop. They’re just like corn, pumpkins, wheat or tomatoes. Most crops we eat can be harvested in months. Trees take years to mature.

If you cut the end off a 2-by-4, 2-by-8 or 2-by-12 you can clearly see the growth rings of the tree. You’ll see dark and light rings of wood. The light colored wood is produced in the spring when the sap rises from the roots and the tree starts another season of growth. This period of growth is usually very rapid and the tree adds girth because water is usually more abundant in the spring.

Once summer rolls around, the tree realizes that water is not as plentiful and that fall is around the corner. The tree gets prepared to shut down for the most part for winter. This is when growth slows and the darker, denser summer wood is produced. Each year of growth adds two rings to a tree, one light and one dark.

I’ve seen pieces of lumber where the lighter spring wood – that’s just four months of growth – is nearly 3/8-inch thick. That same distance on an older piece of lumber would encompass 10 or more years of growth.

The spring wood in lumber is the wood that rots first. It’s less dense, and water rapidly soaks into it. Wood-destroying insects and fungus love to devour spring wood before trying to go after the denser and darker summer wood.

You can soak lumber in a simple solution of borate chemicals to help prevent damage from insects and most wood-rot fungi. Borates are very safe for humans and other mammals.

To soak the lumber in the borate solution, all you have to do is build a simple trough with some 2-by-6 or 2-by-8 material set on edge. Drape some heavy clear plastic into the trough and mix up the borate chemicals with water. Drop the lumber into the borate solution for about 90 seconds, allowing the chemical solution to soak up through the end grain.

Stack the soaked lumber in a shady spot so it’s flat and put in small pieces of lath or sticks so that air can circulate around the pile. Allow the lumber to dry naturally so the borate chemicals stabilize in the wood.


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