Rats and Mice in Richmond Crawl Spaces

A lot of homes in the Richmond area sit over a crawl space: city bungalows in Northside and Forest Hill, row houses with rear additions in the Fan and Church Hill, and mid-century ranches in Lakeside and Bon Air. That shallow, dark space under the floor is one of the best rodent habitats in a house. It is sheltered, often damp, full of pipes and ducts to travel along, and connected to the rooms above through every plumbing and wiring hole.

If you have mice in the kitchen or rats under the floor, the crawl space is usually where to start. This article covers how rodents get in, the signs to look for, and how to clean and seal the space.

Why rodents choose crawl spaces

Crawl spaces give rodents three things at once: shelter from weather and predators, moisture, and quiet. Richmond's humid summers keep many crawl spaces damp, which suits rats because they need water daily. Fiberglass batts between floor joists make easy nesting, and the space is rarely visited by people.

Rodents also use the crawl space as a hub. Norway rats come in from burrows in the yard. Mice come in through vents and gaps and then climb up into wall voids, kitchen cabinets and bathrooms through openings around pipes, drains and ducts.

How they get in

The CDC lists crawl space and attic vents, gaps between the foundation and the ground, and holes for electrical, plumbing, cable and gas lines among the outside spots to check. In Richmond crawl spaces, the usual openings are:

• Foundation vents with rusted, bent or missing screens.
• Access doors that do not latch or have gaps at the frame.
• Gaps where the AC line set, dryer vent or water line passes through the foundation wall.
• Settled or missing mortar in brick pier and curtain wall foundations.
• The joint between an addition and the original house, common on older city homes.
• Openings around a sump pit or drain line.

University of Nebraska extension notes that rats can enter through openings larger than 1/2 inch, and the CDC says mice can fit through a 1/4 inch hole.

Signs of rodents under the house

You may not want to go down there, but you can often tell from above:

• Scratching or thumping under the floor at night.
• Mouse droppings in kitchen and bathroom cabinets next to pipes.
• A musty or urine smell coming through floor registers.
• Pets interested in a floor vent.
• Burrows along the outside of the foundation.

If you or a technician go in, look for droppings along the sill and pipes, tunnels in insulation, torn vapor barrier, chewed flexible ductwork and nests in insulation batts.

Cleaning up a soiled crawl space

Do not crawl in and start pulling insulation. The CDC warns against sweeping or vacuuming droppings and nests because it can put virus particles into the air, and recommends extra precautions for heavy infestations. A crawl space with months of rodent activity is usually a job for a provider with respirators, disposable suits and bags.

A typical cleanup removes droppings and nests after wetting them with disinfectant, pulls soiled insulation, disinfects joists and pipes, and replaces a torn or soiled vapor barrier. See attic and crawl space cleanup for what to ask for.

Sealing the crawl space

• Replace vent screens with heavy wire mesh. The Richmond City Health District recommends screening vents and windows with heavy wire mesh, preferably in a sheet metal frame.
• Fix the access door so it latches tight, and add a metal strip where rodents have gnawed the frame.
• Seal pipe and line penetrations through the foundation with mortar, metal or hardware cloth.
• Seal the holes where pipes and wires go up into the house with copper mesh and sealant, or metal patches. The health district suggests covering openings around pipes with sheet metal or filling them with concrete or mortar.
• Fill gaps in brick and block with mortar.

Do this after trapping, so rodents are not sealed inside. Our exclusion page covers timing and materials.

Moisture matters too

A damp crawl space keeps odors active, makes insulation sag and gives rats water. If you see standing water, wet insulation or a torn vapor barrier, mention it to the provider. Gutters that dump water by the foundation and grading that slopes toward the house make crawl space moisture worse. Some homeowners add a new vapor barrier or dehumidification after a rodent cleanup; that is a separate trade, so ask who handles it.

Questions people ask

Related reading

• Attic and crawl space cleanup
• Rodent exclusion and sealing
• How to get rid of mice in Richmond
• Dead rodent smell