Wood boring insects can be quite destructive causing significant amounts of damage and going undetected for long periods of time. This was exactly the case with a recent project that I was called to help a local client with. Initially, I was only asked to assess powder post beetle damage, but I decided to bring the Resistograph along for the inspection anyway. What I found was more damage than was initially thought, because it was hidden.

For the most part, powder post beetles are typically just a nuisance. They are relatively small, causing 1/16" to 1/8" diameter holes in wood and for the most part their presence is detected by the tiny formations of powder below infected timbers. I have damaged timbers in my own home which is over 100 years old. Photos 1 and 2, below, are from timbers in my basement. As you can see the holes are relatively small and they don't damage much of the cross section. We haven't had any active beetle damage since we've owned the home because the moisture content is too low for their survival and our basement is relatively dry. However, in a damp basement they can remain active for decades and eventually result in pretty significant damage. In this case, the client recently purchased a historic home with a pretty damp basement. Based on the report provided by a home inspector, he recommended that a professional inspect powder post beetle damage that he had observed in the first level timbers.

Photo 1 - Here are exit holes caused by powder post beetles on a timber in my basement.

Photo 2 - Here are the powder packed holes caused by the beetles as they mature prior to laying eggs and then exiting the timber as an adult. As you can see the damage is limited to the outer 1/4" of the timber.

When I got to the clients home there wasn't much powder post beetle damage of concern. To me, it looked pretty typical for an old home. The damage was primarily limited to the outer 1/4" of the timbers. I decided to use the Resistograph to demonstrate the damage present so I tested one girder. The beetle damage was found to be pretty limited, however, what caught my attention was a rather large void that was detected in center of the girder at the mid-span in the middle of the basement (Photos 3 and 4).

Photo 3 - First level girder with powder post beetle damage on the surface. Resistograph testing indicated a void in the center of this element at the mid-span in the center of the basement which was later found to be the result of termites and wood… — Photo 3 - First level girder with powder post beetle damage on the surface. Resistograph testing indicated a void in the center of this element at the mid-span in the center of the basement which was later found to be the result of termites and wood decay (see photo 4).

Photo 4 - Void detected in the center of a girder at the mid-span. Void was found to be the result of termite attack and wood decay.

Based that first drilling I quickly surmised that the damage in the timber was associated with termite attack and wood decay. It doesn't happen often, but when the conditions are right, I have seen termites attack timber in buildings as high as the third level. After I performed a closer examination along the foundation wall it became very evident that wood decay and termite attack was prevalent in several timbers, but was pretty well hidden. The attack appeared to be the result of many years of the vegetation growing on the exterior of the residence, as well as poor drainage (see cover photo). Termites and wood decay often go hand and hand. Both need sufficient moisture to survive, and termites prefer decayed wood because it's easy to consume.

In addition to issues that I found around the perimeter of the residence, I also found that untreated lumber was used to repair certain sections of the floor system by the previous owner. That lumber was in direct contact with the foundation wall resulting in termite attack and wood decay. In one built up girder, there was virtually no material remaining where the girder was embedded in the exterior foundation wall (Photos 5 and 6). Voids were found a significant distance along the length of this element.

Photo 5 - Untreated lumber embedded in the foundation wall of the first level floor system. Significant wood decay and termite damage was detected inside the pocket by testing the built up girder with the Resistograph.

Photo 6 - Little to no resistance detected in built up girder inside foundation pocket. Indicates advanced wood decay.

In the end, I was glad I brought the Resistograph to the inspection. Based on the results of the testing, I was able to detect a lot of hidden insect and wood decay damage. Since the inspection, the client has already removed a significant portion of the landscaping around the perimeter of the residence and improved drainage helping to dry out the basement. Additionally, the compromised elements in the floor system will be sistered or removed, greatly improving the integrity of the floor system.