How to Evaluate and Prevent Structural Damage from Insects and Rot, fungus, Termites, Carpenter Ants, Powder Post Beetles, and Leaks or Water Entry in Buildings

Termitedfs How to spot & prevent termite damage on buildings
How to spot powder post beetle damage and determine its activity
Spotting rot and structural rot damage on wood structures
Inspecting for mold as a clue to building rot, insects, etc.
Identifying harmless desert termites – that don’t attack buildings

This article provides insect & rot damage photographs, inspection advice, and lists additional articles that discuss the inspection, detection, prevention, and repair of structural damage from insects (termites, carpenter ants, carpenter bees, powder post beetles, and other wood destroying insects), indoor mold, rot and building leaks or water entry. These include house damaging mold or fungus, termites, carpenter ants, powder post beetles, & other wood destroying organisms in and on buildings.

We are also concerned with choosing mold and insect damage repair and prevention methods which avoid unnecessary application of chemicals or other environmental impacts. Preventing these problems by good design and by building maintenance is preferred to simple chemical applications around a property. When use of pesticides is required, there are some important choices.

See ROT, FUNGUS, TERMITES for termite and other wood destroying insect information in depth, including termite inspection case reports, field photos and advice. More installation details for termite shields and other building flashing can be found at FLASHING WALL DETAILS.. Readers concerned about termite damage associated with foam, fiberglass, or other building insulation materials should also see Insects & Foam Insulation. Also see TERMITE SHIELDS vs TERMITICIDE for a discussion of termite shields and insect attack on buildings using foam board foundation insulation.

Also see SLAB INSULATION, PASSIVE SOLAR, PASSIVE SOLAR. Readers should also see INSULATION LOCATION for CAPES, CRAWLSPACES, and may also be interested in the mold resistance properties of Icynene Foam Spray Insulation. Finally, because insect damage on buildings is very often related to locations of water leaks or moisture traps, readers should also see WATER ENTRY in BUILDINGS.

© Copyright 2011, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Termite Damage Case Report – Termite Activity Went Un-Noticed

David Grudzinski

I found this termite damage in a house yesterday. The shelter tubes were so large, they were hanging out of the wood. The termites have been in this house for many years, and this sign is that there is a large infestation that has caused sever damage to the house. The main 10×12 center structural beam was so damaged, that about 3/4 of it will have to be replaced.

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This is a significant structural issue with a house. If the homeowners had known what to look for, this may have been caught before the damage was so severe. As you can see form the cob webs, they rarely went there, and did not clean well, so the damage was missed until it was severe.

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We provide a more lengthy case study of a termite inspection that found severe, covered-up and improperly-repaired termite damage at Termite Damage Case – Severe Damage. There photographs show a sequence of clues leading to the discovery of the termite problem.

Termite Damage Mud Tubes Photographs Suggest Where to Look

Our termite damage photograph at below left illustrates that carpenter ant activity (frass or loose “sawdust) may be found in the same location as termite activity (the mud tubes).

Our second termite mud tube photo (below right) is more clear and shows branching termite mud tubes running along the surface of a floor joist.

Watch out: termites prefer to tunnel inside of wood and can cause extensive damage without appearing readily on the wood surface. Mud tubes are typically built to enable movement across a less hospitable surface such as masonry walls or wood that was just not so nice to penetrate.

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Below our termite mud tube photos illustrate how extensive branching mud tubes may be found on building foundation walls headed for wood framing members and even along metal pipes. At below left it appears that termites entered through a crack in the foundation wall, then built mud tubes upwards looking for a more hospitable wood material.

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Below our termite mud tube photos illustrate the importance of a careful, expert termite inspection. The mud tubes at below left are close to and tightly located against the junction of subfloor and rim joist, and the butt end of a floor joist and rim joist and are not as easy to spot as our earlier termite photographs.

And at below right we demonstrate that termites might run along the interior of an old wooden beam; we found these termite tunnels by probing inside the large open checking or splits that would normally be considered not a structural concern, but adding termite damage can change that evaluation. See Splits in Structural Wood Beams for more about log and beam checking or splitting.

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Termite Damage Indicators, Inspection Clues, Photographs

Our photograph at below left shows two signs that should tip off any inspector of a high risk of hidden insect damage: the wood siding is brought close to the ground, perhaps also at a building corner where a downspout or roof drainage spills. Water plus wood plus proximity to the ground surface add up to a high risk of insect attack. Add the observation that an amateur-workmanship wood “skirt” was nailed against the bottom of the foundation, very possibly covering up damage, and this is a red flag for termite or carpenter ant attack.

Our second insect damage risk indicator is the photo at below right: a collection of pesticides, some of them perhaps old and no longer permitted for use by homeowners, found in the building is often a clue that termite or other insect poisoning or treatment was performed by someone other than a licensed pest control applicator – risking not only incompetent ineffective work, but possibly environmental contamination that can be a risk even to the building occupants.

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Photo Guide to Termite Mud Tubes Outdoors

Arizona_Termites_144_DJF_MGsss Our termite mud tube photos just below were contributed by our Arizona correspondent (and daughter) Mara Gieseke, Tucson AZ who reports

So what do you think of these Arizona Desert Termites … I went out back today to try and get some pictures for you. I got one photo of the termite mud tubes that are on a masonry retaining wall that is quite a distance from our house. Then I swiped my shoe over the mud trails that I saw in the dirt, but there were no termites in any of them. Where did they go? The other time I kicked open a termite mud tube there were at least 50 Arizona termites squirming in the mud.

[Mara Gieseke’s termite photo (left) shows Arizona termites squirming in the sunlight just after she disturbed their ground-surface mud tube. We have enlarged this photo to make the termites easier to see, but notice how difficult it is to spot them against the sandy soil found in the Tucson area. How big are termites in actual life-size?

If you could get these termites to line up in single file and march across a U.S. dime, you’d see that if they marched along the diameter of the dime there would be at least five of them. Typical termites are 5.5 mm in length but vary in size from about 1/8″ long to as much as 3/8″ for the big boys. Queen termites are bigger, over 3/4″ in length excluding a pregnant queen’s abdomen that, if included can make her total size 2″ or even more. There are about 2800 termite species that have been identified, grouped in seven families (including the largest family, Termitidae), and it is probable that there are other species not yet classified.]

The retaining wall is 20 feet from the house, and we found tubes growing vertically in the grass too. I also got a picture of a section of dirt that has lots of those mud trails.

We’ve have never had termite activity inside the house. The first year that we lived here we had to have the pest control people out here several times to treat the expansion joint where the back patio meets the house.
Some Termites do Not Attack Structures – Gnathamitermes tubiformans Desert Termites Photos

A local exterminator visited this site and identified the termites in our photographs above as Desert Surface Termites [or by some sources just “desert termites” or Gnathamitermes tubiformans.] Gieseke passed on these details: desert surface termites, according to local exterminator Truly Nolen, are fatter than other types of termites. They do not attack structures. If you were to leave a 2×6 piece of wood in the yard, they would cover it with their mud but they would not eat into it. They would just eat the very outer layer.

Bottom line: desert termites may not attack your building, but they may eat your plants.

Gieseke’s photos below show the mud tubes of Desert Surface Termites on the ground surface near Tucson AZ.

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More about Desert Termites is provided at our references below.

In general, termites’ natural home is in the soil where they attack wood below ground, coming up to higher wood found where there is convenient access, and, depending on the species, moisture.

Your termites are almost certainly subterranean termites as you are finding them living in the ground. (Drywood termites, unlike subterranean termites, do not require direct access to a moisture source and are often found attacking wood above ground level.) Perhaps when you first disturbed the mud tubes on the ground, soil moisture had been so great (following recent rain in Tucson) that your local subterranean termites were coming to the ground surface.

In most of the U.S. only subterranean termites are found, but along the U.S. southern border (including southern Arizona) and further south, both drywood and subterranean termites may be found. In North america north of the U.S. termite damage is less common.
What Happens if We Disturb Termite Mud Tubes

Disturbing a termite mud tube is shown just below. They won’t bite you, but some genera/species of termites will indeed bite a wood structure or its wood siding or trim. If you disturb a mud tube and termites fall out you know for sure you’ve found an active colony. Unfortunately the converse is not necessarily true. If you disturb a mud tube and don’t see any termites, you’ll need more information and probably a more expert inspection before you know if there is ongoing termite activity or not.

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Drill Marks May Mean Amateur Termite or Other Insect Extermination Attempts that May be Unsafe

Below left our photograph shows homeowner-drilled holes in a building rim joist – perimeter framing. This do-it-yourself termite treatment involved drilling and spraying a termiticide or chemical onto and into the wood. Because of the age of the home (1700’s) and amateur work, we were concerned that Chlordane, a toxic, now banned termiticide may have been used as this chemical was previously available for easy purchase in home and garden centers.

Indeed, our test-cut sliver of test wood taken rom the rim joist was confirmed by a chemical test laboratory as having been soaked with Chlordane – a toxic chemical with a long half-life. The building needed further evaluation for the extent of chemical contamination in order to decide if remediation (removal or sealing of treated wood) would be needed.

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Our second termite treatment clue photograph (above right) shows a drill mark in a concrete and slate patio outside and abutting a home foundation wall. Regularly spaced drill openings, 18″ to 24″ apart in a concrete basement floor slab set just inside the foundation wall, or around the outside of a foundation where sidewalks, driveways or patios are installed, are a likely indicator that a professional PCO has pumped a termiticide barrier around the building.

This means you will want to inspect the structure for prior termite damage in order to be sure that further repairs or treatment are not needed.

At Carpenter Bee Holes & Powder Post Beetle Holes we show other holes in wood that are made by insects but that are sometimes mistaken for electric drill holes.

Carpenter Bee Holes & Powder Post Beetle Holes – Old House Borer Damage Photographs

At Drill Marks we show drill marks in wood caused by an amateur pest treatment attempt. While to an experienced eye, holes in wood caused by insects are easily distinguished from those caused by humans using a drill or hammer and nail, on occasion someone is fooled. Here we illustrate two cases of holes that are caused by insects, not mechanical events on buildings: powder post beetle holes in wood, and carpenter bee holes in wood.

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In our powder post beetle photos above, while there was significant beam damage, the infestation did not appear active.

Powder post beetle damage is typically treated with a topical insecticide spray. Some pest control operators (PCOs) also spray paint the wood surfaces in order to make it easier to spot a renewal of insect activity in the future.

We look for the presence of fine wood powder around the insect exit holes or on the ground below the damaged infected member as indications of recent insect activity.

Termite Bait Traps as a Method for Termite Control

One method for stopping or avoiding termite attack on buildings involves the placement of termite bait traps around the building.

Below are two photographs of termite bait traps to help you recognize termite bait traps when you see them.. This approach avoids placing a chemical barrier around the building to stop or prevent termite attacks. The termite bait trap approach relies on regular trap inspection by the pest control operator. When termites are discovered attacking one of the wooden bait stakes, the stake is replaced with one containing a chemical intended to poison the termites.

If the termite bait trap system is not being regularly inspected, you have put out termite-attracting wood around the building perimeter without following through with the proper steps, and in our OPINION you may actually have increased the risk of a termite attack. Be sure your termite bait trap system is being inspected regularly.

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Guide to Use of Termite Shields on Building Foundations as a Termite Barrier

Figure1-3e As discussed in Best Practices Guide to Residential Construction:

Metal termite shields are widely used atop foundations in the southern United States and in tropical climates as a physical barrier to termites. They sit directly on top of foundation walls, piers, and other supports before the first piece of wood is installed (see Figure 1-3 at left).

At one time termite shields were thought to block the entry of subterranean termites, the most widespread and destructive wood-boring insect in the United States. However, subterranean termites, which nest in the soil, will exploit the tiniest gaps in termite shields or other barriers to reach the wooden portions of a house and will build tunnels along exposed foundation walls and around termite shields if necessary.

Although the shields do not stop termites, they slow down their progress and force them to build their tunnels in the open where they can be easily seen during inspections.

To work at all, the termite shield must have tightly sealed joints and be sealed around foundation bolts and other penetrations. Joints can be either soldered or mechanically interlocking. If the barrier is unsealed, termites will find any small gaps and render the effort worthless.

Below our termite mud tube photos show that a termite shield appears to have been installed along most but not all of the building foundation top. Or was it? We don’t know if this is wall flashing that leaves sills exposed just under the wall edge, or whether the flashing extends across the foundation to the interior (as recommended).

But our second termite photo (below right) shows a termite mud tube ascending the same foundation wall and passing under the termite shield. The shield makes it more difficult, but not impossible, for termites to attack a building.

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* All above information and pictures provided by – link to
all information Buzz Kill Pest Control has 20 years of experience in treating termites in the Dallas Fort Worth Texas. We provide termite control and termite services for commercial, residential and industrial structures in both pre-construction and post construction phases of building. We offer liquid or conventional treatments along with baiting systems that include products like Termidor, Talstar, Advance Termite Bait System and Firstline Termite Defense System.

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