What should be placed under the floor to prevent mice? - briefly
Install a continuous steel‑grade rodent barrier, such as ¼‑inch hardware cloth, across the crawl‑space floor and seal all openings with caulk. Add a moisture‑resistant, closed‑cell foam insulation that offers no nesting material.
What should be placed under the floor to prevent mice? - in detail
A solid barrier beneath the flooring is the most reliable method for eliminating rodent ingress. Install a continuous sheet of metal flashing, such as 0.5 mm stainless‑steel or galvanized steel, extending at least 6 inches up the wall and overlapping seams with a stainless‑steel sealant. The metal must be welded or mechanically fastened to prevent gaps.
Complement the metal liner with a closed‑cell polyurethane foam insulation layer. The foam should be at least 1 inch thick, applied directly over the metal and trimmed flush with the subfloor to avoid protrusions that could be chewed. Closed‑cell foam does not provide a food source and resists moisture, reducing conditions that attract mice.
Seal all joints and penetrations using a rodent‑grade silicone caulk. Apply the caulk in a continuous bead around pipe sleeves, vent openings, and where the subfloor meets the foundation. Verify that the caulk remains flexible after curing to accommodate slight structural movement without cracking.
Consider adding a perimeter drip edge of copper or aluminum flashing around the foundation walls. The edge should be bent upward to create a physical overhang that deters climbing rodents. Secure the edge with corrosion‑resistant fasteners and seal the attachment points.
A summarized checklist:
- Metal flashing (stainless or galvanized) covering the entire subfloor perimeter
- Closed‑cell polyurethane foam insulation, ≥1 inch thick, laid over the metal
- Rodent‑grade silicone sealant on all seams, joints, and penetrations
- Copper or aluminum drip edge installed around foundation walls
- Corrosion‑resistant fasteners and welded connections for all metal components
Regular inspection of the barrier system is essential. Look for any signs of wear, rust, or compromised seals, and repair immediately to maintain an uninterrupted defense against rodents.