Finding ants marching out of a crack in the basement wall, or earwigs gathering along the slab, often gets homeowners in Watchung looking at their foundation more closely. Cracks do give pests an easy route inside. But before you grab a tube of sealant or call anyone, it helps to know what kind of crack you have, because the right first call depends on it. Below we'll walk through which pests use foundation cracks, how to tell a cosmetic crack from a structural one and what to do about each. When the structure is sound and the issue is pest entry, our home pest proofing service is built for exactly that.
Which Pests Use Foundation Cracks
A crack in concrete or block is a narrow, protected passage that often stays cool and damp. That suits a lot of pests:
- Ants follow cracks and joints to reach food and moisture inside.
- Earwigs, millipedes and crickets are drawn to the damp conditions that cracks can create.
- Spiders follow the insects and set up along the crack line.
- Mice can squeeze through gaps far smaller than you'd expect, especially where a crack meets a pipe, sill or other opening.
- Subterranean termites live in the soil and can travel through cracks in foundations and slabs to reach wood. Mud tubes along the foundation are a warning sign.
If earwigs are the main thing you're seeing, our post on why earwigs suddenly appear in a house explains the moisture link in more detail.
Cosmetic Cracks Vs. Structural Cracks
Not every crack is a problem for your foundation. Concrete shrinks as it cures, and thin hairline cracks are common in basement walls and slabs. Other cracks can point to movement or pressure that a pest professional shouldn't be the one to judge.
| Usually Cosmetic | Have It Evaluated | |
|---|---|---|
| Width | Hairline, thin and even | Wide enough to fit a coin, or getting wider |
| Direction | Vertical or slightly angled | Horizontal, or stair-step through block joints |
| Wall shape | Wall is flat and straight | Wall bows, leans or one side is offset |
| Other signs | None | Sticking doors or windows, recurring water, crumbling concrete |
If your crack falls in the right-hand column, contact a foundation contractor or a structural engineer first. They can tell you whether the wall needs repair and how it should be done. Sealing over a structural crack to stop ants can hide a problem that needs real attention.
Signs Pests Are Using A Crack
You won't always see the pests themselves. Look for the clues they leave behind along the crack and the wall around it:
- Ant trails running into or out of the crack, or small piles of soil or debris pushed out of it
- Webs and shed skins gathered along the crack line, which tell you insects are passing through
- Droppings or gnaw marks near the base of the wall, which point to mice
- Mud tubes, pencil-width tunnels of soil running up the foundation, which are a sign of termites
- Damp spots or a musty smell near the crack, which mean moisture is getting in and will keep drawing pests
If you see mud tubes, don't break them open and seal over them. Leave them in place so a professional can confirm what's going on.
Why Cracks Draw Pests In
It's not just about the opening. Cracks often let water seep through, and damp soil and damp basements attract moisture-loving pests. Gaps where the foundation meets the siding, sill plate or utility lines add more ways in. Mulch, leaf litter and plants piled against the foundation give pests shelter right at the entrance.
What You Can Do Yourself
- Check the crack type first. Use the table above, and call a structural professional if you're unsure.
- Seal small, stable cracks. Hairline and other non-structural cracks can be filled with a concrete crack sealant made for the purpose.
- Close the other gaps. Seal around pipes, wires and vents where they pass through the foundation.
- Manage moisture. Keep gutters clean, extend downspouts away from the house and grade soil so water flows away.
- Pull back mulch and plants. Leave a strip of bare ground or gravel next to the foundation so you can see what's moving along it.
When To Call A Pest Professional
Once the structure is sound, or the crack is clearly cosmetic, a pest professional can help with what's using it. Call if ants or other insects keep coming in after you've sealed the obvious cracks, you see signs of mice, or you spot mud tubes on the foundation. EcoFusion's NJ DEP-licensed technicians inspect the interior and exterior, find entry points and conducive conditions, seal entry points with pest-resistant materials and apply targeted treatment with EPA-registered, eco-safe products where needed. We don't evaluate or repair structural damage, so we'll tell you if something looks like it needs a structural professional.
Foundation cracks are an easy way in for pests, but the first question is always whether the crack itself is a problem. Get structural cracks looked at by the right expert, seal the small ones and keep moisture away from the walls. If pests are still getting into your Watchung home after that, EcoFusion Pest Control can find the route and close it.