Rats in the Attic:Signs, Entry Points & Removal

You can tell rats are in the attic by the size of what they leave behind. Rat droppings are blunt, about the size of a small raisin according to Penn State Extension, and Cornell University measures roof rat droppings at about 1/2 inch and Norway rat droppings at 3/4 to 1 inch. Mouse droppings are 1/8 to 1/4 inch, so anything clearly longer than a grain of rice points to a rat.

Gnaw marks are the second check. Cornell puts the paired tooth grooves of an adult rat at 3.5 to 4 millimeters wide, against 1 to 2 millimeters for a mouse. Look on the edges of the attic hatch, joists near the eaves, stored boxes and the plastic jackets on cable runs.

Then look for these:

• Nests of shredded material near the eaves or in an undisturbed corner
• Droppings collected along rafters and beside stored boxes
• Noises above a ceiling or in the attic, which UC IPM lists as a warning sign

Photograph droppings with a coin beside them for scale instead of picking them up. That photo answers most of the species question before anyone climbs a ladder.

Roof rats use attics because they are climbers that nest off the ground. UC IPM describes them as “very agile climbers” that “usually live and nest above ground,” favoring attic spaces, walls and false ceilings. To a roof rat, a dry attic is the indoor version of a tree canopy.

That does not mean every attic rat in Chesapeake is a roof rat. A Virginia Tech and Virginia State University IPM guide names two main pest rats in Virginia: the roof rat and the Norway rat. Virginia’s Department of Wildlife Resources adds that the black (roof) rat is “on the decline in Virginia, with displacement by R. norvegicus,” the Norway rat.

Norway rats “generally build their nests in subterranean or ground level locations,” according to the same Virginia Tech guide. Because the same guide says rats can climb almost any vertical surface, a Norway rat colony living under a deck or along the foundation can still send animals up into the roof space.

Species changes the plan. Droppings near 1/2 inch with activity concentrated high in the house suggest a roof rat. Droppings closer to an inch, plus burrows by the foundation, suggest Norway rats using the attic as an upper floor. Those colonies need the ground-level work described on our rat control service page as well as the attic treatment.

Rats get into the roofline by traveling along lines, fences and branches, then squeezing through a gap at the eaves, a vent or a roof penetration. The Internet Center for Wildlife Damage Management notes roof rats “use their tails for balance while traveling along overhead utility lines” and “frequently enter buildings from the roof or from accesses near overhead utility lines.”

The common routes onto a Chesapeake roof are:

• The overhead service line running from the pole to the house
• Fence tops that run close to a wall, which UC IPM notes rats travel along at dusk
• Branches that touch or hang over the roof, and vines on walls
• Downspouts and rough siding or brick

Distance does not stop them easily. Virginia Tech’s guide says rats can jump vertically at least 24 inches and horizontally at least four feet.

Once on the roof, the opening can be small. Texas A&M AgriLife Extension says a roof rat can get in through “a hole the size of a quarter,” and lists “venting and flashing on the roof” among the most likely entry points. With 81.0% of Chesapeake’s housing units single-family homes, per Census estimates, most roofs we inspect are detached houses with exposed edges on every side.

Rats damage attics by gnawing, nesting and fouling everything they live on. The gnawing is the serious part: Virginia Tech’s IPM guide states that “the gnawing on wire insulation can result in electrical shorts and fires.” The same guide lists wood and plastics alongside wiring as materials rats gnaw.

Stored belongings suffer next. Cornell’s IPM program photographed rats “nesting in this and other file boxes that were undisturbed near a reliable food source,” which is exactly what holiday decorations and archive boxes in an attic become.

Insulation takes the rest. Rats pull it into nests and foul it with urine and droppings, and the soiled patches usually have to come out once the colony is gone.

If you find chewed cable, keep clear of it and have it checked before anyone handles it. For what to check on a gnawed cable, read how rodents damage electrical wiring.

Professionals remove attic rats by trapping them on the elevated routes they already use, treating nesting sites and adding exterior bait stations, then checking back. Placement is everything. UC IPM recommends setting roof rat traps in “off-the-ground locations such as ledges, shelves, branches, fences, pipes, or overhead beams,” and Texas A&M advises placing them where droppings are found, “usually along rafters or next to stored boxes.”

Trap size matters too. NC State Extension warns that mouse snap traps are not effective for rats, so a hardware-store mouse kit is the wrong tool for an attic rat.

Texas A&M also advises checking traps often, “daily is best.” That is the practical hurdle for most homeowners, because it means a ladder trip into the attic every day.

That daily check, plus knowing which runs to trap first, is where a professional visit earns its cost. How Chesapeake Rodent Control handles it, step by step and with prices, is on our attic rodent removal page.

Seal the attic after removal by closing every roofline gap with materials rats cannot chew, starting only once the population is being removed. Sealing too early traps a live colony inside the house.

Virginia Tech’s guide lists the best materials for large holes as hardware cloth, “19-gauge or thicker sheet metal, plaster, or mortar,” with caulk or copper wool for smaller holes. The same guide says to look for holes “not only in the first three feet above the ground,” because rats will use a gap at roof height as readily as one by the foundation.

Priorities on the roofline:

• Gaps where the service line and cables enter
• Roof and gable vents with torn or missing mesh
• Flashing gaps around chimneys and plumbing vents
• Gaps around the garage door, which Texas A&M lists as a likely entry point

For the full exterior seal, see our rodent proofing service.

Cleanup is needed whenever rats leave droppings, urine or nests behind, and that is the norm once a colony has nested overhead. Removal and sealing stop new damage, but they do nothing about what is already in the insulation.

Health is the reason. The CDC says people get hantavirus from contact with rodents, “especially when exposed to their urine, droppings, and saliva,” and that symptoms usually appear 1 to 8 weeks after contact, starting with fatigue, fever and muscle aches.

If the attic has more than a few droppings, our rodent droppings and nest cleanup service handles it after removal. When you are ready to deal with the rats themselves, start with a call about getting rats out of your attic.