Rodent exclusion is the permanent fix that turns recurring rodent service into a one-time job. Trapping and bait kill the rodents in the house today; exclusion seals the entry points so new ones cannot get in. In Michigan, mice need any gap larger than 1/4 inch and rats need any gap larger than 1/2 inch — about the size of a quarter. The checklist below covers the 11-step inspection BTR uses, the materials that actually work, and why professional exclusion lasts.
Exclusion vs Extermination: The Core Concept
Most pest companies offer extermination. BTR offers both, and treats them as separate problems. Extermination removes the active population — bait stations, snap traps, multi-catch traps, and monitoring during a treatment window. Exclusion seals every gap that rodents used to get in. Without exclusion, extermination is recurring: new rodents find the same entry points the old ones used, and the home stays vulnerable to next year's fall migration. With exclusion, a single rodent service can be the last one.
For an active rodent infestation, you usually need both. For a home that has not yet seen rodents, exclusion alone is the prevention play. Either way, the work must be done before the Michigan rodent migration begins — usually the first week of October when overnight lows drop below 50°F.
The 11-Step BTR Exclusion Inspection
This is the methodical sweep that catches every entry point. Bring a flashlight, a quarter (for gap-size reference), and the materials listed in the next section.
- Full exterior walk. At dusk, walk every wall and corner of the foundation. Use the flashlight at a low angle — gaps cast shadows. Mark every opening larger than a quarter (rats) or a dime (mice).
- Foundation joints and settlement cracks. Hairline cracks at corners and brick-to-block transitions; pack with mesh + sealant for anything wider than 1/4 inch.
- Sill plate / band joist gaps. Where the wood frame sits on the foundation, especially in older Wayne and Oakland County homes. These often have continuous gaps under the siding edge.
- Garage door corner seals and bottom sweep. The triangle between the door and side jambs is BTR's most common rodent entry point. Install rodent-rated corner brushes; replace the bottom sweep if daylight shows.
- Utility penetrations. Gas, electric, cable, water, and AC line chases. Cut out the existing expanding foam (mice and rats both chew through it), pack with copper wool, then re-finish with exterior-grade sealant over the wool.
- Dryer and bathroom vent hoods. Replace plastic flap-only hoods with metal-mesh hoods that close fully when the appliance is off.
- Weep holes. Brick weep holes need stainless-steel mesh inserts that allow water out but stop rodents from entering.
- Attic vents. Gable, soffit, and ridge vents need 1/4-inch hardware cloth where the original screen is missing or damaged. Inspect from the inside with the flashlight to catch daylight.
- Roof line + chimney. Rats can climb brick and travel along utility wires. Check the chimney cap, flashing seal, and any roofline gap from a ladder.
- Interior monitoring stations. Set unbaited multi-catch traps in the garage and basement after the seal work is done. Anything caught means a missed gap.
- Re-inspection 30 days later. Walk the exterior again. Building settlement and weather can open new gaps. Annual fall inspection is the maintenance habit.
Materials That Actually Work
| Material | Use | Why It Works (or Does Not) |
|---|---|---|
| Copper wool | Utility penetrations, small gaps | Does not rust, holds shape; mice and rats will not chew through it. |
| Stainless-steel mesh / hardware cloth | Larger gaps, vent screens, weep holes | 1/4-inch openings stop mice and rats; stainless does not corrode in Michigan weather. |
| Exterior-grade sealant | Finish layer over mesh / wool | Waterproofs the seal and adds aesthetic finish. Never as the only barrier. |
| Expanding foam (alone) | Insulation only | Does not stop rodents. Mice and rats chew through it within days. Acceptable as a backer with mesh + sealant overlay. |
| Standard steel wool | Short-term only | Rusts within months and falls out. Copper wool is the long-term replacement. |
| Rodent-rated corner seals | Garage door corners | Brush + rubber profile that compresses against the door. Standard weatherstripping does not stop rodents. |
Why Professional Exclusion Lasts
BTR exclusion work uses rodent-rated materials installed correctly the first time — mesh + wool + sealant in layers, not foam alone. A typical BTR exclusion holds for 5+ years in Michigan weather. Building settlement and new construction can open new gaps, so an annual inspection is good practice. Every BTR exclusion comes with a written report identifying every gap that was sealed, the materials used, and any future-watch items.
For an active infestation, exclusion pairs with BTR rodent control for a complete fix. Mice service starts at $235 with a 90-day warranty; rat service starts at $239 with 6 months of monitoring. The full rodent control cost breakdown covers what is included.
Mice vs Rats: Different Gaps, Same Materials
House Mouse
1/4-inch gap (dime width). Curious, investigates new objects within 24 hours. Travels along walls and prefers cover.
Norway Rat
1/2-inch gap (quarter size). Neophobic, avoids new objects. Strong climber, travels along utility wires and brick.
Frequently Asked Questions
What is rodent exclusion?
Rodent exclusion is the process of sealing every entry point larger than 1/4 inch (for mice) or 1/2 inch (for rats) so rodents cannot get into the home. It uses rodent-rated materials — copper wool, stainless-steel mesh, and exterior-grade sealant — in layers. Done correctly, it lasts 5+ years.
What is the difference between exclusion and extermination?
Extermination kills the rodents in the house today using bait, traps, or both. Exclusion seals the entry points so new rodents cannot come in. Without exclusion, extermination is recurring. With exclusion, it becomes a one-time job. For an active infestation, you usually need both.
Can rats be excluded the same way as mice?
Yes, with one adjustment: rats need any gap larger than 1/2 inch sealed (mice need 1/4 inch). The same materials work — copper wool, stainless-steel mesh, exterior-grade sealant. Rats are also strong climbers, so the inspection has to include the roof line, chimney, and utility wire attachment points.
Will expanding foam stop rodents?
No. Mice and rats chew through expanding foam within days. Foam is acceptable as a backer or filler in combination with metal layers (copper wool or steel mesh), but never as the only barrier. Every rodent-rated seal needs a metal layer that rodents physically cannot chew through.
How long does professional exclusion last?
BTR exclusion work using rodent-rated materials installed correctly typically lasts 5+ years in Michigan weather. Building settlement and new construction can open new gaps, so an annual fall inspection is good practice. Every BTR exclusion comes with a written report identifying every gap sealed.
When should I have rodent exclusion done?
Before mid-October, when Michigan rodents begin moving indoors. The most reliable schedule is September for inspection and exclusion work, then October's exterior treatment, then a November re-check. For an active infestation, exclusion should happen alongside rodent service rather than waiting for the population to be cleared.
How much does professional rodent exclusion cost?
BTR exclusion estimates are free with any rodent service and are quoted based on the number of gaps found during the inspection. Most Metro Detroit homes need between 5 and 15 individual seals. Pricing is per-gap rather than flat-fee because every home has a different exterior profile. The estimate is written and itemized.
Get a Free Exclusion Inspection
Free inspection. Written estimate. Licensed Michigan applicators.
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