Wood Destroying Inspects (WDIs)

Wood destroying insects (abbreviated WDIs) can do extensive damage to a home if left unchecked and permitted to continue for a period of time. Almost every home is potentially susceptible to these insects. The four types of insects commonly referred to as wood destroying insects are termites, carpenter ants, carpenter bees, and wood boring beetles.

In PA, in order to perform Wood Destroying Insect (WDI) inspections, most lenders will require that the inspector also be licensed to apply chemicals (pesticides). Some home inspectors are also PA licensed pesticide applicators although we don’t apply pesticides professionally, yet we are required to be insured and trained to do so. The PA Department of Agriculture licenses pesticide applicators. The official Wood Destroying Insect Inspection Report form (aka NPMA-33) should be used for WDI inspection reporting, and is often required by many lenders. The WDI inspector/pesticide applicator should include his license number on the form where indicated. It can be construed as a potential conflict of interest to inspect for and treat the same home for WDIs.

The inspection for wood destroying insects (WDI) is outside the scope of a home inspection, however some inspectors, as noted above, provide Wood Destroying Insect (WDI) inspections as an add-on or ancillary service.

For the vast majority of homes that I perform the home inspection, I also perform a WDI/Termite inspection. Some people also call these a ‘wood infestation’ or ‘pest’ inspection. The purpose of a WDI inspection is to determine if there are any visual indications of a current or past infestation by looking for the common signs that these insects often leave behind. Similar to a home inspection, a WDI inspection is also non-invasive in nature and is performed without moving furniture, stored items, insulation, ceiling tiles, etc. The inspector can only inspect what he can see and access.

It is estimated that over $3 billion per year is spent on WDI treatment. If proper routine maintenance is done by a home owner, the amount and severity of most WDI infestations could be lowered a great amount. All wood destroying insects are looking for wood for one of two reasons: to consume the wood or to nest in the wood. Making conditions so that insects can’t readily access wood around your home is a great way to lower your chances of being infested.

One of the most common ways to help prevent wood destroying insect infestation and damage is to ensure that all vegetation is trimmed away from your home and roof. Too often I find ivy, bushes, or tree branches making contact with the home. This vegetation can provide a direct avenue from the ground into the home and make it harder for the inspector to find visual evidence of an infestation.

Another easy method is to ensure that there is no contact of wooden building materials (such siding and trim) to the ground around your home. There should be, at least, 4” of clearance between the bottom of siding and trim and grade (dirt, mulch, paving, patios, etc.). These clearances can also help prevent water entry or rotted wood. Many landscapers and home owners throw mulch against the home’s siding with little regard to the fact that they’ve created a perfect entrance for insects into a home. If wood rot is found at the home’s exterior, prompt repair is recommended since the rotted wood can also attract wood destroying insects because it is easy to damage and provides a moisture source as well. Keeping firewood stored outside well away from the home above ground and covered is also key to preventing an insect infestation.

A third common reason why wood destroying insects are attracted to a home is improper drainage. This is most often related to clogged or improperly pitched gutters, downspouts that empty along the home’s foundation, and improper grading that allows water to run towards the home. Clean gutters and downspouts that empty, at least, 4’ from the home is recommended.

Inspecting for wood destroying insects in the cold weather months (approximately October to April in our area) often will have little chance of finding an active infestation but may present evidence of a past infestation and/or damage. Most wood destroying insects go dormant in the cold weather months, so they most often won’t be in the home in these colder months and won’t often be readily detected if inspected for at that time of year. I’ve been a PA Dept. of Agriculture licensed WDI inspector/pesticide applicator since 2002.

Termites –

Termites are the most common insect that can do extensive damage to a wooden structure since termites actually consume the wood (the other WDIs are nesting in the wood). The type of termite commonly found in south central PA is the subterranean termite. They often like to set up their colonies near a food and water source. Termites will most often need a few years to do considerable damage to a home which is why regular inspections are a key way to help prevent this damage. Approximately 600,000 homes in the USA are damaged each year by termites. Each year, termites and carpenter ants cause an estimated $30 billion in damage to buildings and farm crops.

In the photos above, the first photo is a closeup of termites in action. The 2nd photo shows shelter (mud) tubes which termites use to leave wood and go scavenging for food, wood, etc. The 3rd photo shows wood siding with extensive termite damage.

Termites and carpenter ants look considerably different and should not be confused. Termites have a single non-segmented body (commonly light cream in color) with straight antennae whereas carpenter ants are a darker color (dark brown or black) have a segmented body and angled (bent) antennae. Termites and carpenter ants both swarm when looking for new nesting areas (this often occurs in the spring). If you find piles of discarded wings, that’s a good sign that you’ve had an infestation. Termites have 4 similar-size wings (2 on each side) whereas carpenter ants have 2 sets of wings different-sized wings.

(the above photo is courtesy of AmericanPest)

When termites move around, they often will do so within wood but if they exit a piece of wood, they need to build small tunnels in order to protect their delicate bodies from drying out in the air. These tunnels are commonly called shelter tubes or mud tubes, are most often a light-brown color, and often are approx. 1/8-1/4” in width. Sometimes these tunnels will only run a short length where the termites exited and re-entered the wood and other times they can run several feet. Sometimes these exploratory tubes will literally extend down or stick up several feet from a piece of wood almost like stalagmites or stalactites you’d find in a cave.

I’ve seen entire wooden joists that have had all of its cellulose removed and there is little left of the wood. Probing this severely damaged wood with a screw driver or awl gives a crinkled sound similar to making a ball of paper in your hand. When you find wood in that condition, it has no ability to provide any structural support. A wood destroying insect inspection (which uses form NPMA-33) is not a structural evaluation nor a structural certification and, if wood destroying insect damage is found to a structural component (such as a joist or beam), the inspector will most often recommend a qualified contractor evaluate the damage and determine if repairs are needed depending upon the severity of the damage. Remember that a WDI inspection, just like a home inspection, is a non-invasive visual inspection meaning even if the inspector sees some WDI damage, additional adjacent damage (sometimes extensive and sometimes minimal) may exist but may not be visible. Some lenders will require a structural certification from an engineer, such as for some government-insured loans. Home inspectors are not structural engineers and are not, in most cases, licensed, insured, nor trained to provide structural certifications in the Commonwealth of PA. Some inspectors provide them but these structural certifications may not be worth the paper they are written on.

An inspection for wood destroying insects will entail a thorough examination of the perimeter of the home’s exterior where the home and grade meet as well as looking at the visible wood structure inside the home. If termite damage is found and there is no evidence that a termite treatment has previously been performed by a licensed exterminator, the inspector will most often recommend that a termite treatment be performed. A termite treatment will most often be a liquid treatment performed around the home’s entire perimeter underground although another less-commonly used method consists of bait stations located at several locations around the home’s perimeter exterior. If you see nickel or quarter-sized patches of concrete in a patio often spaced about every 18″ or so, that is often indicative of a prior termite treatment. Even if evidence of a past treatment is found, the inspector will not necessarily know when the treatment was performed or if the treatment is still actively working, in most cases.

Carpenter Ants –

Carpenter ants are another common type of wood destroying insect. These insects are often about ½” long and most often are black. Carpenter ants look like a giant version of the smaller ‘black ants’ that we often see scurrying around on sidewalks. Unlike termites, carpenter ants do not consume the wood but rather are nesting in it. Generally, carpenter ants do not tend to do the amount of damage that a termite colony can do, although treating a carpenter ant colony can take some skill and luck.

Besides finding wood damage, seeing frass a common indicator of carpenter ant infestation. Frass looks like small light brown or grey pieces of sawdust. When carpenter ants are nesting in a piece of wood, they remove these small particles out of the wood to allow space for the nest and often deposit the frass outside the nest. Like termites, rotted wood inside or outside a home can attract carpenter ants so prompt repair of such is important. Leaks from the roof and plumbing can also be a common cause for why carpenter ants are attracted into the home. A carpenter ant will eat pretty much anything that a human will eat.

Like when searching for termites, probing exterior wood is most often done to find soft damaged wood. When soft wood is found, if carpenter ants are also found, there’s a good chance that this may be the location of the colony. Unlike for termite treatments, carpenter ant treatments are most often done locally to where the colony or nest is found. If carpenter ants are found inside a home, their main nest is most often located outside. An interior nest is most often a satellite nest.

Carpenter Bees –

Like carpenter ants, carpenter bees do not consume wood but rather are trying to nest in it. Areas of wood siding and trim are the most common locations where carpenter bees can be found. They often will bore a ½ to 3/4” diameter hole and then turn either right or left to continue along the grain of the wood. Often a short distance further is where their nest is located. Carpenter bees resemble bumble bees but instead have a black shiny tail section. They will most often be seen hovering near wooden trim, railings, fascia, or soffit boards. Also, finding coarse sawdust or droppings beneath the hole are often signs of carpenter bees.

Male carpenter bees do not have stingers but this doesn’t mean they won’t harass other insects or people who happen to be near their nest. Females do have stingers but rarely use them. Like carpenter ants, damage caused by carpenter bees tends to not be terribly extensive in most cases and treatment normally consists of a pesticide applied at the area of the nesting/bore hole(s). Preventing carpenter bee infestation can be difficult, however minimizing the amount of exposed wood on the home’s exterior and keeping it well stained or painted can help minimize carpenter bee infestations. After a carpenter bee infestation is treated, the hole(s) should be sealed or screened over or the wood can be altogether replaced. Oil-based stain or paint can sometimes help deter carpenter bees from infesting wood.

Wood Boring Beetles –

Wood boring beetles can infest wood floors, furniture, wood trim, etc. Most types of wood boring beetles are in the range of 1/4” to ¾” long in size. Exit holes are often about the size of a pinhead. Complex galleries are sometimes found in lumber. They can also be brought into modern homes inside of old furniture, for example. They often nest inside of wood and lay their eggs; most beetles will not infest wood that has been painted or varnished. Exit holes may have small amounts of frass inside or outside of them depending upon the beetle species. An infestation of beetles into a home often happens due to larvae infestation into the lumber prior to construction. Determining how recent a beetle infestation occurred can sometimes be found by looking at the color of the frass.

Newer infestations tend to have fresher light-colored frass (like brand new cut saw dust) and the sign of an older infestation is often a darker (older-looking) frass appearance (or sometimes the frass has been cleaned up and is no longer visible). Treatment for beetles can be local to the infested lumber or a full fumigation may be needed in some cases. Most wood boring beetles do not re-infest the same wood, although some varieties of beetles can do so.

For more info, consult the National Pest Management Association (NPMA).

Matthew Steger is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), and an electrical engineer. He can be reached at matthew@thehomeinspectorsnotebook.com. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.