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Old-Growth Wood: What It Is and Why It's Worth Keeping

In many older homes, original wooden window sashes may be constructed from a different type of wood than can be found in modern buildings: old-growth wood. While some homeowners may have heard of this material before, others may not know exactly what makes it so valuable.

Old-growth wood refers to wood from trees that belonged to forests that grew up over hundreds of years. A majority of today’s lumber is harvested from trees that have been cultivated to grow rapidly, so the wood is not as dense. As a result, it is weaker and more susceptible to decay and instability. Old-growth wood has nearly ten times the number of growth rings per inch (meaning that it is much denser) and is more resistant to decay or damage. According Scott Sidler of The Craftsman Blog, old-growth wood has distinct advantages over today’s wood: it is resistant to rot and termites, stronger and harder, and more stable.

Stability refers to how much the wood expands and contracts due to moisture. In New England, where the temperature and humidity can vary significantly throughout the year, it is especially beneficial to have wood that can stand up to very dry or very wet conditions. The result is longer-lasting paint jobs, less movement, and fewer gaps during the cold and dry months.

Preservation contractor Bob Yapp recounts an experience that many can relate to: “I can't tell you how many historic houses I've pulled the 1950s aluminum siding off to find the original old growth siding and trim. After repair and a good paint job, this wood will last another 100 years and can yet again be restored. I call that a lifetime product.”

If a wooden window sash in an older home is showing signs of deterioration, one’s immediate conclusion may be that it’s time to replace the old material with a new wood or vinyl frame—especially if you've been bombarded by advertisements for replacement windows. But, if a 100-year-old wood sash is restored and maintained, it can potentially last another 100 years. The outside of the dense wood may appear to be in poor shape, but the inside could still be in excellent condition. Add a good-quality storm window and weather stripping, and the energy efficiency is virtually as good as replacement windows.

Old-growth wood is reparable, and the effort is well worth it to preserve a high-quality building material that is no longer easily available. Wood repair epoxy (such as Flex-Tec) is an excellent choice for making these repairs.

—Sean Yarolin