Roof Rats: Roof Entry Points and How to Seal Them

It's about the roof and its edges: how rats get up there and in, and what closes the openings. Rotted fascia and eaves, which leave openings of their own, are covered in dry rot in fascia, eaves and roof sheathing, and what vents need in a fire zone is in ember-resistant roof vents.

• Trees and plants. Branches that touch or overhang the roof. Los Angeles County says roof rats can jump as far as 4 feet from branches to rooftops, and often shelter in Algerian ivy, bougainvillea and the dead fronds of palm trees.
• Wires and fences. UC IPM says they're often seen at night running along overhead utility lines or fence tops.
• Pipes and walls. The county says they climb pipes and wires.
• Food nearby. UC IPM says roof rats routinely travel up to 300 feet or more for food and favor fruit and nuts, including avocados and citrus, so they may live in one yard and feed on the fruit trees of another.

At each opening, look for what the county lists as signs of use: rub marks, the darkened patches or streaks left where dirt and oil from rodent fur rub off at entrance and exit points, and chips of gnawed material. The tile row comes from a wildlife-damage handbook chapter (Baker, Bodman and Timm, 1994), which says tile or shake roofs let rodents in where the roof isn't solidly sheathed and the tile isn't properly fitted and grouted; the tile industry's manual calls for closures at the eave on high-profile tile, as covered in Spanish tile roof care.

• Metal, not foam or caulk. UC IPM recommends steel wool, wire screen or sheet metal, because rats can chew through plastic, foam, wood and caulk. The county names 1/4-inch mesh metal hardware cloth and sheet metal.
• 1/4 inch is the line. The county says openings as small as 1/4 inch can admit mice and a 1/2-inch gap lets young rats in, and tells owners to eliminate all gaps greater than 1/4 inch. UC IPM says the same: holes larger than 1/4 inch should be sealed to exclude both rats and mice.
• No chicken wire. UC IPM says never to use lightweight chicken wire, since rats pass through its openings.
• Vents still have to breathe. Screen a vent; don't seal it shut. The code already limits attic vent openings to between 1/16 and 1/4 inch, or requires a screen to that size (CRC 2025, R806.1), and sets a minimum vent area that counts only the open area left after screens (R806.2). A screen added over a vent reduces that area, so check it against attic ventilation requirements. In a fire zone, vents on the roof need 1/16- to 1/8-inch metal mesh, finer than the county's 1/4-inch line.

• Branches 6 feet back. The county says limbs should be trimmed at least 6 feet from roofs, attic vents, eaves and utility wires, and UC IPM says overhanging limbs within 6 feet of a roof should be removed, which keeps tree squirrels off the roof too.
• Palm fronds and vines. The county says to remove dead palm fronds and thin ivy and other thick vegetation. UC IPM names climbing ivy, star jasmine and honeysuckle on fences or buildings as plants to thin or remove.
• Utility wires. If roof rats travel along overhead utility wires, UC IPM says to contact a pest professional or the utility company. Leave any branch near a power line to the electric utility.
• Fruit. The county says to remove ripe and fallen fruit.

• Noises from the attic or ceilings; UC IPM says rats are mostly active at night.
• Droppings, shredded insulation or nests in the attic.
• Rub marks and gnawing at openings along the roof edge.
• Rats running along utility lines or fence tops at dusk.
• Hollowed-out oranges or eaten lemon rinds still hanging on the tree, which UC IPM describes as roof rat feeding.

It's worth acting on early: UC IPM says roof rats living in an attic can cause considerable damage and safety concerns, including electrical sparks and fires, from their gnawing and nest building.

So when you hire out the trapping and the rodent-proofing, they go to a registered pest control company; its license can be checked through the Structural Pest Control Board. A roofer's part is the roof: replacing broken vents, adding closures at tile eaves, replacing rotted fascia and eave boards, and flashing at walls and chimneys, as roof repairs.

If you rent a home in Los Angeles County, the county's public health department takes rodent complaints at 888-700-9995 or online; an inspector may visit and determine whether there's a problem the property owner is required to address.

Trapping. The county says snap traps are preferable inside a building in most cases, because a poisoned rodent may die where it can't be reached and cause odors and flies. Outdoors, it says nearby buildings should be rodent-proofed before any baiting, and UC IPM gives the same order, so poisoned rats don't come inside to die.

Cleaning up. The county's health advisory says rodents in Los Angeles County can carry the bacteria of plague and murine typhus and hantaviruses, spread by flea bites, contact, or breathing in particles from urine, droppings or nesting material. Its steps for cleaning a rodent area:

• Wear rubber, latex, vinyl or nitrile gloves, and don't stir up the droppings and nests.
• Air out an unoccupied space before going in to clean.
• Wet droppings, urine and nests with a household disinfectant, wipe them up with a towel dampened with disinfectant, and seal them in a plastic bag inside a second bag.
• Disinfect and rinse the gloves before taking them off, then wash your hands with soap and water.

The advisory says a dust mask can't be relied on against airborne pathogens, and that for a heavy infestation, especially in a confined space with little ventilation, you should contact the county's Vector Management Program.

Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 9, 2026.

1. University of California Statewide Integrated Pest Management Program, Pest Notes: Rats, UC ANR Publication 74106 (N.M. Quinn; updated June 2025)
2. Los Angeles County Department of Public Health, Environmental Health, Rats/Mice
3. Los Angeles County Department of Public Health, Environmental Health, A Practical Guide to Rodent Control
4. Los Angeles County Department of Public Health, Environmental Health, Are You Attracting Rats and Mice to Your Yard?
5. Los Angeles County Department of Public Health, Environmental Health, Health Advisory: Rodent-Borne Diseases: Risk Reduction Recommendations
6. Structural Pest Control Board, Structural Pest Control Act (Business and Professions Code §8505, §8550, §8555), updated July 2025
7. California Residential Code 2025, Chapter 8, Roof-Ceiling Construction (R806.1, R806.2)
8. Rex O. Baker, Gerald R. Bodman and Robert M. Timm, Rodent-Proof Construction and Exclusion Methods, in Prevention and Control of Wildlife Damage…
9. Tile Roofing Industry Alliance, Concrete and Clay Roof Tile Installation Manual, 2024 edition