How can I seal vent openings in the foundation against mice? - briefly
Fit each vent with ¼‑inch stainless‑steel hardware cloth or mesh, fastening it with exterior‑grade caulk or expanding foam to eliminate gaps. Inspect the seals periodically and replace any damaged sections to maintain a mouse‑proof barrier.
How can I seal vent openings in the foundation against mice? - in detail
Inspect the foundation for any openings where air vents intersect the slab or crawl space. Common entry points include gaps around vent pipes, seams between vent covers and the concrete, and cracks at the perimeter of the vent housing.
- Remove debris – Clear dust, soil, and loose material from the opening to ensure a solid bond with sealing agents.
- Apply a primary barrier – Pack stainless‑steel wool or copper mesh into the gap. These materials are too coarse for mouse teeth to chew and conform to irregular shapes.
- Seal with a rigid filler – Over the mesh, inject a high‑expansion polyurethane foam or a cement‑based mortar. Expand the foam until it fills the cavity completely, then trim excess flush with the vent surface. For mortar, press it into place and smooth the surface.
- Install a secondary shield – Attach a hardware cloth (¼‑inch mesh) or a vent cover with a built‑in screen over the opening. Secure with corrosion‑resistant screws, sealing screw holes with silicone caulk.
- Check for continuity – Run a thin piece of wire or a flashlight through the vent to verify no gaps remain.
Materials to consider
- Stainless‑steel wool or copper mesh – flexible, chew‑resistant.
- Polyurethane expanding foam – fast‑curing, fills irregular voids.
- Cementitious mortar – durable, compatible with concrete.
- Hardware cloth (¼‑inch) – provides a permanent physical barrier.
- Silicone or polyurethane caulk – seals screw heads and seams.
Maintenance recommendations
- Inspect seals annually, especially after heavy rain or ground movement.
- Reapply caulk to any cracked joints.
- Replace damaged hardware cloth promptly to avoid new entry points.
- Ensure vent covers remain securely fastened; loose covers create leverage for rodents.
By following these steps, the vent openings become impermeable to rodents while preserving necessary airflow for the foundation’s ventilation system.