Norway Rat & Mouse Structural Exclusion Detroit

Norway rats (*Rattus norvegicus*) enter structures through openings as narrow as 0.75 inches, while common house mice require only 0.25 inches of clearance. In historic Detroit neighborhoods such as Boston-Edison, Indian Village, and Palmer Woods, older stone footings and brick-and-mortar perimeters develop settling cracks that function as direct conduits into basements. Standard poison baiting fails to correct these vulnerabilities because outdoor rodent pressure remains continuous along urban utility alleys and sewer lines near the Detroit River corridor. Tactical exclusion replaces bait-dependence by establishing physical barriers across foundation weep holes, basement window frames, and sewer stack interfaces.

Properties in Midtown, Woodbridge, and Corktown frequently feature balloon-frame architecture or century-old fieldstone rubble walls. Fieldstone foundations require hydraulic cement packing alongside welded galvanized hardware cloth (19-gauge, 1/4-inch mesh) behind porch steps and ledger boards. In slab-on-grade or crawl-space residences across Bagley, Green Acres, and Rosedale Park, rodent activity centers around HVAC chases, dryer vents, and rotted garage door weather-stripping. Sealing these zones eliminates the entry paths that cause gnawed electrical wiring, nesting in subfloor fiberglass insulation, and food contamination.

Structural exclusion works as a sequential engineering process: 1. A physical transit audit maps active burrow runs, gnaw marks, and entry gaps from roofline to foundation footer. 2. Exterior barrier installation affixes 16-to-19-gauge steel mesh, custom aluminum coil flashing, and pest-grade expanding elastomeric foam across all perimeter voids. 3. Interior containment sets mechanical snap traps within crawl spaces, utility rooms, and attics to capture rodents trapped inside the envelope. 4. Post-exclusion tracking powder and mechanical monitors verify zero movement over a 14-day clearance window.