💡 The Math of Exclusion A mouse fits through a ¼-inch gap. A cockroach fits through a 1/16-inch gap. Most homes have dozens of gaps larger than these at every utility penetration, door frame, and foundation crack. Sealing these is a one-time investment that permanently reduces pest pressure.

Best Materials for Each Job

Material	Best For	Works Against	Longevity
Steel wool + caulk	Pipe gaps, small holes	Mice, rats	5–10 years
Xcluder fill fabric	Larger gaps up to 4" wide	Mice, rats, snakes	Permanent
Galvanized hardware cloth (1/4")	Vents, large openings	Squirrels, mice, rats	Permanent
Silicone caulk	Cracks, small gaps, sill plates	Ants, cockroaches, mice	5–10 years
Expanding foam (pest-rated)	Large irregular gaps (+ steel wool)	Insects (NOT rodents alone)	10+ years
Automatic door sweep	Door bottoms	Mice, rats, cockroaches, ants	3–7 years

⚠️ Expanding Foam Alone Won't Stop Rodents Mice and rats chew through standard foam easily. Always combine foam with steel wool or Xcluder fill fabric for any rodent-vulnerable gap. The foam seals the void; the steel wool prevents gnawing through it.

Priority Entry Points

🚪 Entry Doors (Highest Priority)

Door Bottom Gaps

Shine a flashlight under the closed door from inside at night. Any light = pest entry. Install an automatic door sweep that drops when the door closes. For garage doors, use a brush seal or T-type bulb seal — standard rubber seals leave gaps at the corners where mice enter.

Door Frame & Weatherstripping

Check all four sides of exterior doors. Weatherstripping that shows daylight or that's cracked and hardened needs replacement. V-strip weatherstripping lasts much longer than foam tape. Self-adhesive foam is a temporary fix only.

🔧 Utility Penetrations (Critical for Rodents)

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Under-sink pipe gaps

Pull everything out from under the sink. Inspect where pipes enter through the floor or wall. Mice enter through these gaps nightly — fill with steel wool then foam, or Xcluder fill fabric.

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All other utility penetrations

Every pipe, wire, and conduit entering from outside is a potential pest entry. Walk the exterior and interior, identify every penetration, and seal with appropriate material. Pay special attention to: dryer vent, AC line set, electrical service entry, gas lines.

🏠 Foundation & Sill Plate

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Sill plate gap

The sill plate (horizontal wood sitting on the foundation wall) often has gaps due to settling. Walk the interior perimeter and caulk any gap between the sill plate and foundation. On the exterior, use foam backer rod + caulk for larger gaps.

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Foundation cracks and weep holes

Fill cracks wider than 1/8 inch with hydraulic cement or polyurethane sealant. For weep holes in brick walls (structural — must remain open): plug with copper mesh or Xcluder, which allows drainage but blocks pests.

The Walk-Through Inspection

Interior Priority Areas

Kitchen: Under sink pipe gaps, behind refrigerator and stove floor gaps
Bathrooms: Under sink, around toilet flange, where tub drain meets floor
Utility areas: Washer hose penetrations, dryer vent, water heater pipes, furnace flue
Basement: Sill plate perimeter, all pipe penetrations

Exterior Priority Areas

Foundation perimeter: Every crack, pipe penetration, and sill plate gap
Roofline: All gable vents, soffit vents, and roof-to-wall junctions
Garage: Door bottom seal, all wall penetrations, interior door sweep

💡 Total Investment A complete pest-proofing of an average home takes 3–4 hours and costs $40–$80 in materials. This one-time investment reduces pest pressure more effectively than quarterly chemical treatments — and it lasts for years.