Whenever I inspect an older home that has a newer addition, I usually find that the termites are in the addition, not the original structure. At first, that might seem surprising—after all, the older section has been around much longer. But the difference comes down to the type of wood used and how lumber standards have changed over time.

Older California homes were commonly built with true dimensional redwood. Back then, a 2×4 actually measured 2 inches by 4 inches, and the wood itself was naturally resistant to decay and pests, including termites. Redwood has a lower moisture content and contains natural compounds that make it less appealing to wood-destroying insects.

Newer additions, on the other hand, are typically framed with Douglas fir. Not only are today’s “2x4s” actually smaller (1½ inches by 3½ inches), but the wood itself retains more moisture and lacks the natural resistance that redwood had. That extra moisture content makes it easier for drywood termites to survive and establish colonies.

So, when I see termites in a home that’s half old and half new, the problem almost always lies in the new construction. It’s a good reminder that building materials matter—and that sometimes, the old ways of doing things really did hold up better against nature.