Wood Education
Not all wood is the same wood.
Species, grain orientation, and growth rate determine how a window behaves for the next fifty years. This is the single most underestimated variable in the restore-or-replace decision.
| Species | Density | Decay resistance | Notes |
|---|---|---|---|
| Douglas Fir | Moderate-high | Moderate | The backbone of Pacific Northwest window stock. Strong, stable, and takes a crisp profile. |
| Vertical Grain Fir | High | Moderate-high | Quarter-sawn fir with tight, parallel growth rings — far more dimensionally stable than flat sawn. |
| Hemlock | Moderate | Low | Common in mid-century sash. Machines cleanly but needs a disciplined finish schedule. |
| Mahogany | High | High | The premium choice for exterior doors and exposed sash. Excellent stability and natural decay resistance. |
| Pine | Low-moderate | Low | Widely used and easy to work. Modern fast-growth pine is markedly less durable than old stock. |
| Oak | Very high | Moderate | Very hard and dimensionally strong, typically found in interior-focused or historic assemblies. |
Old growth
Why the wood already in your wall is better than its replacement.
A board milled from a tree that took two hundred years to grow has rings packed tightly together and a high proportion of heartwood — the dense, extractive-rich inner wood that resists both moisture movement and fungal decay. Fast-growth plantation stock reaches harvest in decades, producing wide rings, more sapwood, and markedly lower dimensional stability.
This is why a hundred-year-old sash with a soft bottom rail is usually worth repairing: the failure is localized moisture damage, while the remaining ninety percent of the assembly is material you cannot buy today at any price.
