A house is stitched to the outside world by utilities: gas, water, electric, cable, phone, dryer exhaust and sometimes a drain. Each one passes through the foundation or siding, and the hole around it is usually bigger than the line.
This article walks through the common ones and the materials that close them for good.
How the gaps form.
Installers drill a hole, push the line through and fill the gap with whatever is handy. Over the years, foam shrinks, caulk cracks and settling shifts the line. What began as a tight seal becomes an opening the width of a pencil.
The common gaps.
| Entry type. | Usual flaw. | Stronger repair. |
|---|---|---|
| Gas pipe. | Gap around the pipe. | Steel collar, mesh, sealant (technician for gas work). |
| Water line. | Foam shrinks or cracks. | Copper mesh plus masonry sealant. |
| Electric service. | Loose boot, cable gap. | Sealant and mesh outside the boot. |
| Cable or phone. | Hole drilled oversize. | Packed mesh and sealant. |
| Dryer vent. | Flap stuck, screen missing. | Metal hood with a closing flap. |
| Hose bib. | Gap around the pipe. | Escutcheon and sealant. |
Dryer vents specifically.
Dryer vents are warm, lint-filled and open to the yard. A rodent that finds the flap stuck open can walk into the duct and build a nest, which is a fire hazard as well as a pest problem.
- Check that the flap closes by gravity.
- Replace plastic hoods that have warped.
- Keep lint cleaned from the duct.
- Install a hood with a screen that still allows airflow.
A weekend check.
Walk the outside of the house with a flashlight and note every pipe and cable. Look for daylight, gnaw marks, grease smears and shredded material. Photograph anything odd. Inside, look at the same spots from the basement or utility room.
Do not use steel wool alone. It rusts and can be pulled out. Use copper mesh or hardware cloth as a plug, and cover it with sealant.
Where a technician helps.
A technician carries the right collars, mesh and sealant and knows which gaps matter. The sealing page describes the job, and the inspection page shows how every opening gets listed in the estimate.
Awake at 2 a.m. and hearing scratching? Call anyway.
(888) 686-4821Safety.
Never reach into a gap you cannot see. Rodents bite when cornered. Wear gloves, and leave gas and electrical work to professionals. If you smell gas, leave the house and call the utility.
Keeping finished work in good shape.
After a job is done, the best protection is routine. Walk the outside of the house twice a year and look at each patch of mesh, each strip of flashing and each bead of sealant. Metal that has shifted or sealant that has cracked is an invitation, and a ten-minute touch-up is cheaper than a new infestation.
Keep stored items off the floor of the garage and basement, trim shrubs back from the siding, and fix dripping spigots. Mice and rats follow water, food and cover. Remove two of the three and the house stops being worth the trip.
Pay special attention to the places where a line enters the building, because installers rarely leave a tight collar. Gas, cable, electric and refrigerant lines each punch through a wall, and the gap around them grows with every season of expansion and contraction. A technician can show you how to size a patch for each one.
If you add a new line, such as an electric vehicle charger or a mini split, ask the installer to close the hole behind the conduit with something a mouse cannot chew. Foam alone does not count. Mesh packed into the hole and covered with sealant does, and the extra ten minutes costs very little.
What federal guidance says about cleanup.
Come back here every time pellets, urine stains or bedding scraps turn up.
- A leaf blower aimed into a dusty garage corner is the worst idea, with a household vacuum a close second.
- Plan on thirty minutes of ventilation before any cleaning begins.
- Put gloves on at the beginning, and close out the job with soap and water.
- On a shelf dotted with pellets, work from the outer edges inward so none skitter off.
- Everything the cleanup touched, gloves and towels included, leaves the house in a knotted bag.
- Feeling off afterward? Tell a doctor what the cleanup involved and let the doctor judge.
Federal sources for the steps above.
The pages below, which are open to the public, carry product limits and fuller instructions.
- CDC hantavirus prevention page: A hantavirus summary, with suggestions for keeping rodents out of houses and vehicles.
- Where the CDC explains rodent waste removal: A damp-cleaning routine for homes, each move spelled out.