Addressing Pest Issues in Historic Buildings


Guest post by Danielle Rogers of


Historic buildings are rich with history and character, but when it comes to restoring and finding a new use for them, there is one huge hurdle that many historic building owners face: pests. When buildings sit unoccupied for a long period of time, as many historic buildings do, infestation of pests such as termites, carpenter ants, and Powderpost beetles exacerbates with each month the building is left untreated. These wood-boring pests can cause extensive damage, eating away at the foundation, walls, and joists of buildings, in some cases rendering the space unfit for use. For those interested in preserving and reusing such buildings, it should always be a top priority to address all pest issues promptly and gently so as to not cause further damage or jeopardize health. Here are some pests to look out for when a restoration is about to begin and how to eliminate and prevent them for the long term:


Depending on what area of the country the historic buildings are located, different types of termites may be a threat for structural damage. Subterranean termites are much more common and can be found in all states. They live underground, but that doesn’t mean they are harmless. These termites can collapse an entire building by consuming wood little by little. If you suspect that a building may have a termite infestation, be on the lookout for a swarm of termites. Hit walls lightly and try to detect if it sounds hollow inside. If so, you may have a termite problem on your hands.

Carpenter Ants

Buildings without basements or those located close to a lot of trees are most susceptible to a carpenter ant issue. First, rule out a termite problem by comparing the appearance of these pests. Does the insect concave at the waist or is the entire length of the body a consistent width? If the waist is narrower, those are ants. You can also tell by looking at the antennae. If the antennae are straight, you are dealing with termites. If bent, you are dealing with ants. You will most likely never have both termites and carpenter ants residing in the same areas of a building. Carpenter ants thrive in wood that has been damp for a long time, as they can easily be hollowed out. Look for wood shavings near water-prone areas like faucets, kitchens, and bathrooms.

 Powderpost Beetles

This variety of beetle causes the most damage in larvae form, carving tunnels within wood. Buildings made of maple, beech, poplar, or pine, are most at risk for an Anobid Powderpost beetle infestation. Though most common in the northernmost states of the US, these beetles can live in any buildings with prolonged dampness. If you suspect an issue, look for small holes in wood of the building called “shot holes.” This could be a sign of infestation.

If any signs of damage are discovered in a historic building, immediate action should be taken to prevent further destruction and salvage the landmark. In cases that are not extreme, baiting methods could work, especially for termites. Select bait that contains boric acid and place them in areas that you believe are high in pest traffic. For a more natural alternative, clove oil is toxic to pests and can be sprayed on damp wood without risk of damage. For buildings with extreme pest problems, fumigation may be the only way to completely eliminate the issue and progress with renovation. To do this, it is necessary to hire a professional who can tent the entire building and fumigate it with sulfuryl fluoride or another gas, which will effectively kill all pests within 2 days. After the problems are addressed, preservation can begin. But first, it is important to take measures to ensure that another pest issue doesn’t resurface. Using silicone caulk, close off any openings into the building, especially near ducts and water-prone areas. Replace any wood that has been water-damaged. For a temporary measure, reinforce the damaged wood with other timber that is generally pest-resistant, such as turpentine, tea tree, or cypress. Store rotting wood far away from the building and cut back any tree branches or bushes that are in close proximity. For more pest prevention tips, visit

Don’t let pests stop any preservation efforts! We wish the Preservation Alliance of Minnesota and all historic building owners the best of luck in saving Minnesota’s historic resources and many thanks for the opportunity to be a guest author on the PAM blog today.

Danielle Rogers

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