Demystifying Old-Growth Lumber

"Old-growth lumber" is a term old-house owners and craftspeople often bring up, usually to argue that wood used to be better. It turns out old growth isn't a species or grade of wood — it describes a forest condition. The U.S. Forest Service defines old-growth forests as ones with old trees and structural features that developed over long stretches of time without major disturbance, like fire or logging. Trees in these forests are generally 100 to 150 years old, shaped by competition for light and space as they grew.

Most of the old-growth lumber people prize today was cut down and milled in the 1800s and early 1900s, starting in the eastern U.S. and moving west as forests there were exhausted. By around 1920, more than two-thirds of American forests had been cut at least once. What grew back afterward is called second-growth, third-growth, and so on — and that's mostly what today's lumber comes from.

The upshot for anyone with an old house: the reason old-growth wood is scarce isn't that we've lost the ability to grow it, but that modern forestry doesn't leave trees standing undisturbed for a century or more before harvesting. If you're weighing repairs versus replacement on old timber or trim in your home, it helps to know that what makes that wood distinctive is really its age and growing conditions, not some lost manufacturing technique.