Old Growth Lumber vs. New – Preventing Warping, Twisting and Rot
Old Growth Lumber Grew Slower - Much Slower
Old Growth Lumber - The piece of lumber on the top was harvested from the forest in 2013. The one on the bottom is old-growth lumber taken from the slopes of the Rocky Mountains just after the end of the Civil War or War of Northern Aggression. Photo Credit: Tim Carter
Quick Column Summary:
- Hard to find straight lumber
- Trees are a crop
- New fast-growth trees being cut
- Old-growth lumber rots slower
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, 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, WA
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. I've had the good fortune to take apart many old homes and I made a point to salvage some of the lumber to use as a comparison.
Have You Worked With Old Growth Lumber?
About thirty-five 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, OH. I was transforming a very small bedroom designed as a nursery into a master bathroom and walk-in closet. 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 the center of the tree. I could not see the center of the tree, but the concentric rings weren't that much tighter from one end of the piece to the other. I counted 153 dark growth rings. My guess, based on the shape of the rings, is the tree the joist was cut from was 400 or more years old when it was felled.
Note the vast differences in the thickness of the growth rings on the two pieces of lumber. The old-growth timber with the narrow bands experiences much less movement as it reacts to changes in moisture content. Copyright 2024 Tim Carter
Are Trees Grown For Lumber a Crop?
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. Lumber companies, for years, have hired botanists and chemists to help them shorten the time it takes for trees to mature. The goal has been to get rapid growth so they can harvest a section of land more often.
How Can You Best See Tree Growth Rings?
If you cut the end off a 2x4, 2x8 or 2x12 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.
Why are Growth Rings Different Colors?
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, more dense, summer wood is produced. Each year of growth adds two rings to a tree, one light and one dark.
If you compare lots of modern lumber to the joist I cut off in my former Cincinnati, OH home, you'll see a vast difference in the size and spacing of the growth rings. Older trees didn't seem to grow as fast as modern trees. The more summer wood you have in a tree, the more dense and stable it seems to be from my experience. Look for lumber that has tight and narrow growth rings if you can find it if you want to minimize warping, twisting and bows.
How Thick Can One Season of Spring Wood Be?
Today I've seen pieces of lumber where the lighter spring wood, that's just four months of growth, is nearly three-eighths of an inch thick. That same distance on an older piece of lumber would encompass ten or more years of growth.
You’re looking at an old piece of lumber from the late 1800s versus a modern timber. Look at the difference in the size of the growth rings. Copyright 2022 Tim Carter
What Part of a Piece of Lumber Rots First?
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.
How Can I Prevent Wood Rot?
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. The biggest issue is the chemical is water soluble. This means if you treat a piece of lumber with the borates, and the lumber gets wet from time to time, the water can leach the chemical protection out of the wood. This doesn't happen with modern chemical treatments that are safe for exterior exposure.
To soak the lumber in the borate solution, all you have to do is build a simple trough with some 2x6 or 2x8 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. If you then keep the lumber dry once installed, you'll get years and years of protection against rot and insect infiltration.
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