Rodent Exclusion and Entry-Point Sealing

9:00 AM – 5:00 PM, seven days a week · Free residential inspections and quotes

Trapping deals with the animals already inside a building. Exclusion is the part that decides whether you call again: closing the ways in.

How small is small

The figure that sets the whole job is the size of the gap. The U.S. CDC says mice can fit through a hole the width of a pencil — 1/4 inch, or 6 mm, across. University of California IPM, in its house mouse pest note, gives two numbers: under a gap 1/4 inch tall, such as beneath a door, and through an opening 3/8 inch wide.

Neither of those is a gap you would notice walking past. A door sweep worn back at one corner, the ring around a pipe where the sealant has shrunk, the space behind a dryer vent hood: each is enough. That is why the survey looks for openings rather than for droppings, and why it takes longer than people expect.

The species matters less than you might think at this stage. House mice and deer mice both come through openings of that size. University of California IPM notes that deer mice tend to move into vacated homes, cabins and other buildings to nest and store food — which is the pattern seen in seasonal camps, and the reason a camp closed for the winter can be badly occupied by the time it opens in spring.

The survey

Exclusion is not one price per house. It depends on how many openings there are, how high they are, and whether the material around them is sound enough to hold a repair.

• Ground level. Sill plate gaps, foundation cracks, bulkhead seals, crawlspace vents, and every utility line entering the building.
• Garage. Door bottom and side seals — a frequent entry on a Maine house with an attached garage, and among the cheaper ones to correct.
• Roofline. Soffit returns, the joint where a roof plane meets a wall, lifted drip edge behind gutters, gable and ridge vent screening.
• Penetrations. Dryer vents, bath fan terminations, hose bibs, mini-split line sets, radon piping, electrical service entry.
• Material condition. Rotted sill, soft fascia, failed mortar. These are named as carpentry or masonry before anyone spends money sealing them.
• Grounds. Woodpiles against the wall, feeders, compost, sheds sitting directly on soil.

That list matches the CDC’s own. Outside, the CDC tells homeowners to check the roof among the rafters, gables, eaves and soffits; windows and doors without weatherstripping; the line between the foundation and the ground; and every hole cut for electrical, plumbing, cable and gas lines. Inside, it adds kitchen cabinets, behind appliances, under sinks, around the water heater and furnace, floor and dryer vents, fireplaces, attics, basements and floor drains.

What holds and what does not

Sealing is a materials job. Copper mesh packed tight behind sealant in small gaps. Hardware cloth, mechanically fastened, over vents and larger openings. Sheet metal over anything already chewed. Mortar or concrete patch at masonry. Every repair we quote names the material, so you can check it was done that way.

The published guidance points the same way. The CDC recommends steel wool held in place with caulk or spray foam for small holes, and lath screen or metal, cement, hardware cloth or metal sheeting for larger ones. University of California IPM is firmer still: plastic screening, rubber, vinyl, expanding foam, wood and other gnawable materials are ineffective against house mice, steel wool pads make good temporary plugs, and openings should be sealed with metal or concrete.

So expanding foam alone, loose steel wool with nothing holding it, a plastic vent cover and a bead of silicone across a wide gap are all temporary, and rodents find them within a season.

Sequence matters

1. Inspect, inside and out, and document every opening.
2. Remove the animals that are already inside.
3. Seal, once activity has stopped, working from the confirmed entries outward.
4. Re-inspect, because rats in particular test a repair.
5. Deal with the conditions — the woodpile, the feeder, the bin — or say plainly whose they are.

One household’s experience of that order, quoted word for word:

“Highly recommend this company. They showed up to look at a problem with mice in the wall. They’re knowledgeable and professional. Showed us where the mice were getting in along the foundation and garage. They sealed all the access areas and set traps with results the next day. I’ll call them again if I ever need help with any type of pest control.” — Debbie, April 2026, Google review

Why sealing beats trapping on its own

University of California IPM says a female house mouse may have five to ten litters a year, each of about five or six pups, and that the young can breed five to six weeks after birth. Trapping takes out the animals already inside. It does nothing about the population outside, which will find the same open gap next autumn. A building that stays open is a building that refills.

That is also the health argument. Maine CDC has confirmed two human hantavirus cases in the state, in 2011 and 2025, and after the first of them the UMaine Animal Health Laboratory’s director summed up prevention for Maine residents as keeping rodents out of your house, barn or camp. The U.S. CDC says the deer mouse spreads the hantavirus responsible for most illness in the United States. Exclusion is the step that keeps the droppings out of the space in the first place; if they are already there, see attic clean-outs and sanitation for the safe way to deal with them.

What you can do around the house

Some of the most useful exclusion work is not sealing at all. The CDC recommends:

• Keeping food, including pet food, in thick plastic, metal or glass containers with tight lids.
• Siting compost bins at least 100 feet from the house.
• Moving woodpiles 100 feet or more from the home and raising the wood at least a foot off the ground.

A full 100 feet is not realistic on every Maine lot, and nobody is going to move a woodshed for a mouse. The principle is what matters: anything that feeds or shelters rodents should not sit against the wall you are trying to keep them out of. Every condition of that kind found on the survey is noted, with a plain statement of whether it is ours to fix or yours.

Timing

The cheapest exclusion job is done in September, before the first hard cold pushes rodents toward buildings. The most expensive is done in January, with animals established, insulation already soiled, and half the exterior under snow where a proper repair cannot be made.

If you are reading this mid-winter with noise overhead, the order changes: remove first, seal what is reachable, and diary the rest for the thaw. We will tell you which is which rather than charging for a repair that will not last.

Rural homes and camps

University of California IPM says deer mice are not normally found in residential areas unless fields, forests or similar habitat surround them — which describes plenty of houses outside the town centers.

For camps that sit closed through the winter, the survey is best done before closing up rather than after opening, so the building is shut against the season it is most exposed to.

What you are left with

A written list of every opening found and what each one needs, the removal plan, the sealing quote itemized, and a clear note of anything belonging to another trade. If a second company quotes the same house you should be able to lay the two side by side and compare them line by line. That is the point of itemizing it.

Exclusion sits alongside rodent control, which covers the removal side of the same job. Both are done as licensed pest control work by an insured, owner-operated business.

Free residential inspections and quotes. Call or text Ryan Blouin at 207-740-4441.

Updated 2026-10-04.