How can you seal a ventilation duct in the foundation to prevent mice from entering? - briefly
Fit a metal or rigid PVC collar over the duct opening, secure it with high‑strength silicone caulk and a layer of steel wool or copper mesh, then seal the exterior with concrete or a durable sealant. Periodically check for gaps and repair any damage to maintain a mouse‑proof barrier.
How can you seal a ventilation duct in the foundation to prevent mice from entering? - in detail
Inspect the duct opening where it penetrates the foundation. Remove any debris, nesting material, or gnawed insulation. Use a shop‑vac or brush to clean the surface, ensuring a dry, smooth substrate for sealing.
Choose a combination of barrier materials that mice cannot chew through. Recommended layers, from interior to exterior, include:
- Steel wool – pack tightly into gaps no larger than ¼ in.
- Copper or stainless‑steel mesh – overlay the wool, securing with construction‑grade staples or masonry nails.
- Expanding polyurethane foam – apply a low‑expansion formula (≤1 in. rise) to fill remaining voids, avoiding excess pressure on the duct.
- Cementitious sealant or hydraulic cement – once the foam cures, coat the area with a thin bead of cement that expands as it sets, creating a rigid, waterproof seal.
If the duct passes through a concrete slab, drill a small pilot hole around the perimeter, insert a flexible metal flashing strip, and embed it in fresh concrete or a cementitious patch. Smooth the surface to match the surrounding foundation.
After sealing, verify the integrity by:
- Running a thin wire or flexible probe through the duct to detect any residual openings.
- Inspecting for signs of gnaw marks or fresh droppings over the next few weeks.
Additional preventive measures:
- Install a metal vent cover with a fine mesh screen at the exterior termination point.
- Trim vegetation and remove debris near the vent to eliminate hiding places.
- Maintain a dry environment; moisture attracts rodents and can degrade sealants.
Regularly re‑examine the sealed junction, especially after heavy rains or foundation settlement, and repair any cracks promptly to sustain a mouse‑proof barrier.