Wood destroying insect inspections, or WDI inspections, are usually performed during the home inspections I perform for clients, but can also be performed as a stand-alone service. The National Pest Management Association form used to report the findings and/or evidence of wood destroying insects is called the NPMA-33 form, and is good for 90 days from the day of the inspection. This form is used to report the evidence and/or the existence of four different wood destroying insects:
Termites
Carpenter Ants
Carpenter Bees
Powder Post Beetles
The damage caused by these insects can also be reported on the form, but in most cases, damage isn’t visible or very minor. However, I have observed major structural issues caused by termites, powder post beetles, and carpenter ants. I’ve also observed log cabins, and houses with log cabin siding that was absolutely riddled with carpenter bee exit holes, and an active carpenter bee infestation. Whether, it was a structural issue or not, the carpenter bee damage was extensive, and would be very costly to repair.
Termite Shelter Tubes
Each WDI inspection is unique, due to several factors:
Different types of construction
The location of the home
How long the structure has been infested with one or more of these insects (many times I’ve found and recommended treatment for three of the four insects at one property)
Points of water intrusion that have lead to the infestation
There are homes built on crawl spaces, slab foundations, full basements, or any combination of the three.
All of the above types of construction ( homes built on crawl spaces, slab foundations, and full basements) can pick up wood destroying insects. There are also homes, where the type of structure can be more likely to pick up wood destroying insects. These are mostly the structures that are wood-framed. The exterior wall structure, as well as the floor structure in these homes, are all usually studded walls that sit on top of the foundation, with the floor structure integrated.
Masonry-walled structures became a less common building practice for homes between the 1950’s and 1960’s. These structures have less wood in them overall, and the existing wood is mostly in the floor structure, internal wall structure, and attic. The exterior walls of these consist of brick or block, and is usually tied together from the foundation up to the soffits or gables. These can have furring strips on the exterior walls, used mostly for plaster adherence, but can also be devoid of furring strips if metal lath was used, or if plaster was directly applied to the masonry wall. From my own experience, masonry-walled structures don’t pick up termites as often as a wood-framed structure, but is still very possible.
Termites are usually the most common wood destroying insect that is talked about, and their presence can be alarming to a home owner, or prospective home buyer. Termites don't care what type of structure they're trying to infest. They're just looking for a food source. So, they can be found in any type of structure. I've actually found them in metal-framed commercial buildings, with only wood in the door frames. Guess where I found the termite evidence? Right, the door frames. Usually, in homes, you can find evidence of termites in the floor structure box sills, or on the exposed concrete foundation in an attached garage.
Finding carpenter ants, or evidence of them is more unpredictable due to being an insect that is not subterranean, regardless of the type of structure. They can enter the structure via vegetation overgrowth, in most cases, but not always. Usually, with both of these insects, points of water intrusion will attract them. The water makes the wood soft and/or rotten, which is more attractive to termites and carpenter ants, due to the wood being easier to chew.
Powder post beetles, or re-infesting wood boring beetles, are more rare to find. Usually, only the evidence of their past existence in a floor structure is observed. However, I’ve observed active infestations of these wood boring beetles. They essentially turn the wood to powder, and the wood will be full of tiny holes about the size of a ball-point pen head. All of these insects leave evidence of their existence. Termites build shelter tubes, carpenter ants leave frass, powder post beetles leave frass, and carpenter bees leave frass. Frass is what the insect leaves behind. Carpenter ant frass looks like dirty wood shavings, or coffee grounds, and can contain dead bug pieces and parts. Carpenter bee frass will usually stick to whatever surface is outside the bee exit hole, and usually has a yellow color to it. Powder post beetle frass looks like baby powder, but the color of the board it came out of. All four insects can leave exit holes. Also, dead insects of all four species can be found, but finding dead termites is a whole lot less common. Termites live under the ground in their nesting colony, and come into the home looking for a food source (materials containing cellulose, like wood, drywall paper, etc.). Carpenter ants and carpenter bees find suitable wood to build a nest. With carpenter bees, the female does the damage while trying to excavate the hole for the nest. Powder post beetle larva eats the wood it’s inside of, matures and exits the wood, and then re-infests the wood to lay eggs. It can become a viscous cycle.
All of these insect issues should be treated to protect the integrity and quality of the wood they’re after, even if it’s not a structural problem. Every home owner should have an annual wood destroying insect inspection. I have one last short story to share, to accentuate my point.
In April of 2021, I performed a wood destroying insect inspection for a VA loan, of a house with an unfinished basement. No treatment was recommended, due to the lack of any WDI evidence. In January of 2022, I inspected the same property again, for the same client, for a VA refinance. This time, there were shelter tubes in the rear of the basement floor structure, in a sill box opposite of the rear concrete patio (point of moisture intrusion). I had to deliver the bad news to the client, which in turn had to get the home treated, in order to keep the VA loan refinance process going. This is why annual WDI inspections are important.
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