Inspectors have to determine the cause of damaged wood they find on the exterior, basement, or interior of a house. If the damage is caused by wood destroying insects, then treatment may be necessary, if the damage is caused by wood rot of one variety or another then no treatment is necessary but determining the water or excessive moisture source is very important.
What are the evidence and clues we look for? Let’s start with termite evidence: Seeing live termites or termite wings always wraps the issue up quickly, but that is rare. Termite mud is the most common clue inspectors will find for termite activity or damage, either outside or inside of wood framing members, on foundation walls, or other building components.
Mud is the polite term for what termites excrete as they eat wood. Termites use the mud to build tubes or tunnels for protection and to maintain the high moisture contact they need to survive above ground. So, if an inspector probes wood and finds damage, then finds mud inside or outside the wood, he or she will know it is termite activity. However, another clue damage was caused by termites is the way they tend to eat with the grain and leave thin walls as they go. These thin walls often make a crinkling noise when probed into, which is very distinctive, and there is usually some mud in between these walls.
So, if we find damaged wood with no signs of termite activity then wood rot is a distinct possibility. Wood rot causes wood to shrink, distort, and become very soft and crumbly but also intact to a large degree with no hollowed-out areas or thin walls left behind. Wood fungus, often found in crawlspaces, also causes wood to shrivel and distort but break off in chunks rather than small, wet pieces. Of course, there will also not be mud, powder (from powder post beetles), or sawdust type material (carpenter ant frass) if the cause of the damage is wood rot.
Speaking of carpenter ants, what are the clues these little guys are responsible for wood damage? Carpenter ants do not eat wood as a food source, they hollow out wood for colony space. After they chew and hollow out wood the ants will push frass, which looks like sawdust, out of the nest along with dead carpenter ants. They actually eat their dead and will push out ant body parts. Unpleasant to think about but definitely something to look for to be sure we are not looking at sawdust.
Powder post beetles are very common in old houses because the larvae of these insects live inside trees. The larvae survived in wood framing members in houses built prior to lumber being kiln dried, which kills the larvae. Two clues point to powder post beetle activity: small exit and entrance holes in wood framing and wood turned to powder from the activity. The small holes are made when the beetles bore out of the wood in order to mate and then bore back in to lay eggs. Decades and centuries of this boring in and out can cause significant damage.
The last wood-destroying insect we see is the wood boring bee, also known as the carpenter bee. These insects do not cause structural damage as a rule but most often damage trim, fascia, and soffit boards higher up on a house versus close to the ground. A wood-boring bee is the size of a large bumble bee, and it can often be seen flying around the upper levels of a house. When boring into wood they leave a perfectly round hole, go in an inch or so and turn left or right, and then bore a few more inches, creating space to lay eggs. They often leave very thin walls which break through, creating long jagged sections of wood damage visible from the ground and excrement stains outside the holes.
Hopefully, your next inspection will not include wood damage, but if it does, you now know some clues to look for!