Renovation & Design

Insect entry into home through holes always cause for concern

Question: We have a bay window in the front of our home with plants in front. Last year we had wasps going through the plants, underneath the bay window, with some ending up in our basement. We are looking at getting a plasterer to close up any potential holes under the bay window. Then we are thinking about filling in the area under the window with soil to ensure there is no way for wasps to get in. Is there a reason not to fill in the area below the bay window due to insulation or drainage issues? Or is there a better way to deal with our issue? We tried an exterminator last year with limited success. Thanks for your help with this.

— Richard R.

Answer: Insects gaining entry into the exterior walls or interior of our home should be immediately addressed to prevent damage to the home and occupants. This is normally caused by a new opening and/or moisture damage to existing components. Finding and replacing the damaged materials and sealing the area is a much better approach than using soil to fill in these areas.

Since we are lucky in not having termites, or other insects, in our area that can bore into healthy wood, most insect intrusion into our exterior walls is due to damaged building materials. Some common crawling or flying pests, like carpenter ants, will find ways to infiltrate these areas and make nests. Fortunately, that will only occur in components that are damaged. Most commonly wood or wood products are the preferred target for these small critters. If the wood is partially rotten the ants can bore small openings and channels in the soft material and lay eggs. The eggs will eventually hatch, creating even more of a serious infestation to deal with. The evidence of such an attack can often first be detected by seeing the removed material deposited on the area inside the damaged wood. This sawdust-like material is often referred to as frass. If frass is seen in your home, in addition to the wasps, it is confirmation of the source of the issue.

Stinging insects, like wasps, bees, and hornets, will often make their nests in a hidden area to protect them from predators and environmental elements. This can often be found in a tree, under a deck, in a woodpile, or any other location that has ideal conditions. I recently found an active one at the cottage, under my boat cover, attached to a plastic fender sitting on the rear portion of the boat. Luckily, I saw the wasps flying in and out of this area before removing the tarp. That allowed me to spray some insecticide in the area, before untying the cover, to avoid getting stung. I believe that area was a preferred one for the nest due to protection from most elements by the tarp, which still allowed the area to be slightly damp and very humid. From my experience, wasps prefer to build their nests in somewhat damp areas, but underneath something that will shield it from direct rainfall. Nests are commonly seen on the soffits of homes, at the peak of a gable or near a leaky eavestrough.

In your situation, the location of the nest may be protected by the plants in front of the window. These may not only help to hide the nest, but will also make the area more humid and may have resulted in moisture damage to the exterior components. Any vegetation that is touching the exterior of the home should be removed or trimmed back at least one metre. If the outside of the base of your bay window is wood or plywood, rot is extremely likely. If the wall covering in that area is other siding material, stucco, or masonry, the moisture damage may be hidden, but can still be present. Especially if the underside of the bay window is covered with a wood-based sheathing and is overhanging the foundation, serious damage is almost certain.

After removing the vegetation, visual inspection and probing the surface with a screwdriver or other sharp tool will help determine the extent of the damage. If the probe easily penetrates the surface, immediate repairs are in order. If the surface appears relatively sound, partial removal of the exterior coverings may be required to further explore any inside rot. If there are one or more small areas of damage, gaps, or other openings, that is the likely point of entry for the wasps. Spraying the surrounding area and inside the holes with insecticide should initially be done to prevent getting stung. Follow the directions on the spray can for proper precautions before attempting this yourself, or call an exterminator.

Once the area under and around the bay window is partially opened, the extent of the moisture damage can be determined. The repairs may range from a minor replacement of rotten exterior sheathing, to complete reconstruction of the entire bay area walls and floor. Many times, the window frame or sill may be compromised, which is where the moisture intrusion is initiating. In that situation a new window, with moisture resistant vinyl or fibreglass components, is the required final solution.

Building up the soil under an older bay window that is letting insects gain entry into your home will not likely solve the problem, and can accelerate current moisture damage. Inspection and replacement of moisture damaged components, which may include the window, may be the only way to permanently prevent a reoccurrence.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


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