How Rodents Get Into Garages and Attics

Garages and attics are two of the most commonly infested areas in Missouri homes — and for different reasons. Understanding how rodents access each of these spaces reveals the specific exclusion steps needed to protect them.

Garages: The Most Common Entry Point in Missouri

The attached garage is the single most common pathway rodents use to enter Missouri homes. Several structural features make garages particularly vulnerable:

The Garage Door Gap

Even a well-maintained garage door rarely creates a completely airtight seal at the floor. The bottom seal — the rubber or vinyl strip along the bottom of the door — deteriorates over time and often develops gaps at the corners or along its length. A gap of 6mm (the diameter of a pencil) is sufficient for a house mouse. Replacing worn bottom seals and installing a threshold seal on the floor beneath the door dramatically reduces this entry point.

The Garage Service Door

The personnel door from the garage into the house — or from outside into the garage — frequently has gaps under it from worn weatherstripping. This door connects the garage directly to the living area and is a critical exclusion point. Install a heavy-gauge door sweep and ensure the door closes fully with no visible gap at the floor.

Gaps in the Garage Walls

Garage walls often have gaps around utility penetrations — the electrical conduit from the main panel, water supply lines, natural gas lines, and cable or phone lines. These penetrations are often not sealed at all, leaving a clear path from outside or from the crawlspace into the garage wall cavity and from there into the living areas. Seal all penetrations with caulk, hardware cloth, or rodent-resistant foam.

Gaps at the Foundation

The joint between the garage foundation and the floor slab, cracks in the foundation wall, and the gap where the foundation meets the soil at the exterior are all potential entry points for mice and Norway rats. Inspect the garage perimeter at floor level with a flashlight and seal any gaps found.

Items Stored in the Garage

Once inside, garages offer abundant nesting material — stored boxes, bags of grass seed or bird feed, old furniture, and seldom-moved equipment all provide harborage and food. Organizing stored material into sealed containers, elevating items off the floor, and eliminating food sources (including pet food stored in the garage) reduces what sustains a garage rodent population.

Attics: Roof-Level Entry Points

Soffit and Fascia Gaps

The junction where the roof meets the wall — the soffit and fascia area — frequently has gaps that develop as buildings age and settle. Even small gaps in soffit panels, at the corner where two soffits meet, or where the soffit meets the exterior wall provide attic access. Inspect the soffit perimeter from the outside with binoculars for any visible gaps or missing sections.

Roof Vents

Ridge vents, gable vents, and turbine vents are designed to ventilate the attic but can also allow rodent entry if screening is absent, deteriorated, or has gaps. Check that all roof vents have intact fine-mesh screens. Gable vents are a particularly common entry point — the louvered vents on the triangular end walls of the attic are often not screened and provide direct attic access.

Pipe Boots and Flashing Gaps

Plumbing vent pipes exit through the roof via rubber boots. As these boots age, they crack and shrink, leaving a gap around the pipe that is more than large enough for mouse entry. Roof penetrations for other utilities have similar gap risks. These are best addressed during roof maintenance or by a pest control technician performing a full exclusion assessment.

Overhanging Trees and Utility Lines

Rodents — particularly roof rats and squirrels — use tree branches and utility lines as highways to the roof. Branches within 6 to 8 feet of the roofline should be trimmed back. Utility lines running to the structure can be fitted with rodent guard discs that prevent travel along the wire.

From Garage or Attic Into the Living Areas

A mouse in the garage is a problem; a mouse in the kitchen is a larger problem. The path from garage or attic into the living areas runs through interior wall voids accessed via gaps at the top of interior walls (garage to living area), around pipe penetrations, and through unfinished spaces. Sealing the garage-to-house service door and addressing all penetrations through the common wall between garage and house is the critical interior exclusion step. See our full exclusion guide at rodent exclusion: sealing entry points.