Question: I am wondering if you can possibly answer a question regarding getting rid of my uninvited tenants. I live in the country. An addition to the house was built about 20 years ago. When it was built, my late husband did not want a basement underneath it, which I did not mind. However, neither did he want a 1.2-metre-high crawlspace underneath. Instead, he and the contractor agreed to set the addition on piles. Between the piles are big pieces of pink foam. The footing rests on that and a lintel sort of beam. At that time, we had young dogs who were around all the time, so no critters, other than mice, wanted to live under the home.
Over the years, life changed, and the dog got very old. Other critters decided they would live underneath the addition. I have tried different things for discouragement, but they come back every year. Trap one and another moves in. Now, the gophers chew through the foam and move right in. I thought to dig a 90-centimetre-deep trench along the house and set wire mesh along the foam to deter both gophers and mice. Then, to fasten the mesh with cement to the concrete of the house.
In your opinion, could this solve the problem of squatters?
Kind regards, C.W. De Meyer
Answer: Keeping unwanted pests from entering our homes can be a challenge, especially with homes that have crawlspaces. There is one major key to keeping them out. You have the right idea, but may need additional planning or help to properly execute your plan.
Especially in rural or semi-rural areas, pests such as the rodents you have discovered can be a constant nuisance. In homes that have crawlspaces at or below grade, the chance of intrusion by these furry little guys is multiplied. Most commonly during the winter months, but also at other times of the year, various types of mammals will seek shelter from the elements. One that makes an ideal winter home is an easily accessible crawlspace that is either heated or much warmer than the surrounding environment. Your shallow crawlspace fits into this category, for several reasons.
While the main reason your crawlspace is an ideal choice for pests is warmth, there are other factors as well. Areas like yours below buildings also tend to be damp, which is desirable for many types of intruders. Insects such as wasps, bees, carpenter ants, sow bugs and various others love damp areas. Mammals, like the mice you have previously seen, rabbits, raccoons, skunks and other small, furry critters seem to thrive in the damp environments in crawlspaces. Making attempts to dry out your crawlspace may help make this area less desirable to the intruders.
This can be done by installing a heat source, fans, summer vents and HRV, or other items that improve air movement. Stagnant air will certainly lead to higher humidity and condensation on cold metal surfaces such as plumbing pipes, nails, joist hangers and heating ducts. Installation of a 6MIL polyethylene air/vapour barrier over the dirt floor of the crawlspace will also prevent evaporation of moisture from the soil beneath the house entering this area when it is sealed for the winter.
Once you have successfully dried out the crawlspace, the next item to address is the key to any pest reduction strategy. Ensuring the enclosure for the crawlspace is completely sealed should prevent any and all intruders. Mice, which you seem to have little concern about, can enter through an opening the size of the diameter of a finger. Wasps and other stinging insects, which like to build sizable nests inside areas like that below your home, only need tiny gaps to enter. For larger rodents, like the ground or tree squirrels you mistakenly are calling gophers, bigger entry points are required. The fact they have chewed or clawed their way through the rigid foam sheathing tells me they need larger openings to enter and leave the crawlspace when desired.
The only way I know to ensure there are no openings that allow access under your home is to inspect the entire area below your floor. Looking at the exterior for damaged, rotten or displaced sheathing should yield these answers. Often, entering the crawlspace to look for small gaps is the ideal way to pinpoint the problem areas. Once identified, moisture-resistant sheathing, such as pressure-treated plywood or cement board, should be used to cover the openings. If there are more than a few openings, or the existing sheathing is damaged, removal and replacement may be the best choice.
If the crawlspace is enclosed only by the foam insulation, new sheathing should be installed all around, extending and sealed to the top of the footing, or dug in a few inches below grade if no footing exists.
Squirrels, rabbits, mice and other pests can often dig through soft soil, making it easy for crawlspace entry below even well-sealed skirting. Your idea of digging a trench and installing mesh may work but may be quite labour-intensive. A better solution may be to maintain the soil around this area better or build it up with crushed stone to make digging more difficult. Once these issues have been dealt, with setting some traps inside the crawlspace — in locations where they can be easily removed — should take care of any existing intruders.
Having the occasional mouse sneak into the area below your floor may be a minor inconvenience, but the same root cause that allows that to occur may be permitting the larger rodents to gain entry. Ensuring the exterior skirting of your crawlspace is completely sealed, and the interior dried out at well as possible, should prevent further major incursions from the larger critters you have seen.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358, or check out his website at trainedeye.ca.
trainedeye@iname.com
