Pests in the Crawl Space: Why They Get In and What Helps

An open, damp crawl space can be an easy place for pests to get into and stay. Rodents and insects are drawn to crawl spaces across the Carolinas for the same reasons: gaps and torn vent screens give them a way in, and damp soil, standing water, humid air and softened wood give many of them the conditions they look for.

A crawl space that stays wet through a humid Piedmont summer, or sits damp over a high water table near Wilmington, is usually more attractive to pests than one that is sealed and dry. The same dampness under the floor that softens framing is part of the picture.

Signs often show up in the house first: scratching or movement under the floor at night, droppings near floor registers, and a stronger musty smell. Under the house, the common findings are insulation that has been pulled down or tunneled through, droppings on the liner or soil, chewed duct wrap, and torn vent screens.

Mud tubes on piers or foundation walls can point to termites, and wood that is soft or hollow near damp areas is worth a closer look. If an inspection finds signs of an active infestation, we will tell you, so you can call a licensed pest professional.

Encapsulation is the crawl space work that addresses both reasons pests come in. The foundation vents are closed with fitted, sealed vent covers, gaps at the perimeter are sealed, and a liner covers the ground and runs up the walls. A sealed access door closes the one opening you still use.

With the openings closed, a dehumidifier holds the humidity down and the space stays dry. A crawl space that is sealed and dry offers pests fewer ways in and fewer reasons to stay. Sealing is a preventive step; it does not remove pests that are already living under the house.

An active infestation needs treatment from a licensed pest professional. Sealing a crawl space with pests still inside can trap them there, so treatment usually comes first, and the sealing and drying work follows.

If an inspection finds wood that pests or moisture have weakened, that is a structural question. Joists, beams and posts that have lost strength are repaired through framing repair work.

Homeowners sometimes ask about spray foam insulation on crawl space walls. HydroHelp911 does not install or recommend spray foam in crawl spaces, because it can trap moisture and hide termite activity and wood rot from inspection.

In HydroHelp911's experience, the termite companies it has spoken with will not warranty a crawl space against termites when spray foam is on the walls or floor. If you have a termite bond, ask your provider before any insulation work.

Sealing a crawl space is part of encapsulation, so the cost follows the encapsulation plan: the size of the crawl space, the number of vents and gaps, and whether a dehumidifier or a new door is needed. You receive a written estimate after a free inspection, and our vapor barrier and liner page explains the sealing work in more detail.