February 11, 2026
If you hear strange noises coming from the attic of your Marin County home, look for early signs of rodent activity, such as the times you hear noises, where animals might be getting in, and any physical traces along their likely paths. Daytime running and thumping are usually caused by squirrels, while nighttime scratching is more common with rats or mice. Each species leaves distinct patterns of attic damage, especially in insulation and wiring, and the fix depends on the species you are dealing with.
Rats, mice, and squirrels call for different removal methods and attic exclusion repairs. Squirrels often create or enlarge roofline openings by chewing at soffits, fascia, roof vents, or shingles. Whereas rats and mice usually use existing gaps and spread contamination by tunneling through attic insulation and using the same runways every night.
If you don’t identify which animal is in your home, you may try removal tactics that probably won’t work, and the infestation will continue. Sealing a dime-sized opening might help with mice, but it will not solve a squirrel problem, as squirrels tend to enter through larger roof openings. Trapping approaches designed for nocturnal rodents are also less effective for squirrels, because they are active during the day. Cleanup needs vary, too. While rats typically leave a stronger urine odor than mice, squirrel damage is often concentrated near nests and food stashes.
| Sign | Rats | Mice | Squirrels |
|---|---|---|---|
| Active hours | Night | Night | Day (early morning, late afternoon) |
| Typical entry size | About quarter-size gaps | Dime-size gaps or smaller | Larger openings, often created by chewing through the roofline |
| Droppings | 1/2–3/4 inch pellets, often seen along runways | 1/8–1/4 inch pellets, usually scattered around | Oval pellets, typically found near nests |
| Insulation damage | Tunnels in attic insulation; compressed runways | Tunneling below the surface; shredded nesting pockets | Flattened on top; pulled or shredded near nests |
| Chewing | Wires, wood, and plastic | Wires and soft materials | Wood, rafters, wires, vent covers |
| Nesting materials | Insulation, paper, fabric | Shredded insulation and soft materials | Leaf and twig nests; nut or acorn stashes |
Rat noises from attics are usually more noticeable at night, when rats are active. Look for droppings along walls, pipes, and beams where rats may travel. You may also see dark brown or black rub marks where their bodies repeatedly brush framing, ducts, or rafters. Rats can enter through quarter-size gaps, often starting at the lower parts of the home before moving up into the attic space.
Gnawing is constant. Rats chew electrical wires, PVC, and wood, creating fire hazards and water damage. Fresh shavings, chewed edges on stored items, and damaged duct wrap are obvious signs of active travel. Rats can also cause a strong urine smell because they mark their routes with urine.
Rat-induced insulation damage can look like tunnels and compacted tracks. Compressed insulation loses loft and insulates poorly, leading to uneven temperatures throughout your home and higher energy use. When rat urine in attic insulation goes untreated, the odor can spread into your living space.
If droppings and urine are widespread, attic cleanup after a rodent infestation typically involves removing insulation rather than simply spot-cleaning to avoid potential health risks. Even after trapping, contaminated insulation can retain odors and may attract future infestations if rodent entry points are not properly sealed.
Mice are nocturnal, so activity tends to happen at night, but the noise they create is much quieter compared to rats and easier to miss. Mouse droppings are smaller and may appear scattered instead of concentrated along one obvious runway.
Because mice can squeeze through very small gaps, they tend to enter around utility penetrations, vents, and seams where materials meet. Once inside your home, they shred paper, fabric, and insulation to build nests and can even chew wiring.
Damage to attic insulation caused by mice is often hidden within loose-fill insulation. They tunnel beneath the surface, so the top layer can appear normal from the attic hatch while contamination spreads below. If odors persist or droppings are found across multiple areas, replacing insulation after a rodent infestation is often the cleanest way to remove contaminated material and restore coverage.
Mice also reproduce quickly. If entry points remain open, a minor issue can develop into a major problem within a short time because rodent populations increase rapidly.
If you have squirrels in your attic, they usually make noise during the daytime. Homeowners often hear running, rolling, or jumping sounds coming from the ceiling, especially early in the morning and late in the afternoon. Squirrels typically need larger access points and may chew through roof vents, soffits, fascia edges, or shingles to get inside your home. Once they have an opening, they are likely to keep making it bigger.
Squirrel attic damage can include chewed wood, torn vent covers, damaged ducting, and chewed wires. You can find their nests by looking for materials like leaves and twigs. You may also find nut or acorn stashes, which can attract insects or other pests after squirrels are gone.
Squirrels often stay above the insulation and flatten it around their nesting areas instead of tunneling underneath. Flattened areas lose loft and can create hot or cold spots in the rooms below. Urine odor can accumulate near nests, though it is often less concentrated than heavy rodent tunneling.
Because squirrels create larger roofline openings, squirrel-exclusion attic work may require repairing shingles, soffits, or vents, as well as screening. If insulation is heavily soiled or crushed near nests, insulation replacement in those zones can restore performance and reduce odor.
We recommend calling for help if you find chewed wiring, a persistent odor that does not clear, widespread droppings, or recurring activity. Visible roofline holes, ceiling stains, or noises after sealing entry points can mean that animals are still inside or that other access points were missed.
A thorough inspection should confirm the species, identify entry points, and estimate the contamination level to ensure the scope aligns with the problem.
North Bay Rat and Rodent provides free inspections in Marin County. The team combines exclusion and repair work with insulation replacement after a rodent infestation, restoring the attic once the animals are out.
We determine whether the issue is caused by rats, mice, or squirrels, then locate entry points and document insulation and structural damage.
We use trapping and removal methods that are appropriate for the species and the situation.
Droppings, nesting materials, and contaminated insulation are removed, and then we disinfect the area using dust-control practices.
We seal off entry points with rodent-resistant materials and repair larger openings at the roofline, vents, or soffits.
We remove damaged material and install new insulation to restore coverage and energy performance.
Tree coverage and roof access routes can make attics easier for squirrels to reach. Rats and mice may reach upper areas by following utility lines, fences, or dense landscaping. Older homes can also develop gaps over time as vents wear and exterior seals fail, allowing rodents and squirrels access into the home.
If you suspect that rats, mice, or squirrels are living in your attic, schedule a free inspection with North Bar Rat and Rodent. With our services, you will receive a clear plan for exclusion, attic cleanup after rodent activity, and insulation replacement if the insulation is contaminated.
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