Los Angeles County Public Health describes rats as broadly distributed throughout the county. Two species do almost all the damage to homes: the roof rat and the Norway rat. They look similar at a glance, but they live very differently.
Roof rats: the climbers
- Look: slimmer, darker (often black or dark gray), with a tail longer than the head and body together.
- Where they live: up high. Palm trees, ivy, bougainvillea, fruit trees, attics and the upper parts of walls.
- How they get in: along fences, power lines and branches onto the roof, then through gaps at the eaves, torn vent screens or openings around pipes and cables.
- Where in Los Angeles: the main problem in inland and hillside neighborhoods with mature trees and older homes.
- Signs: noises overhead at night, droppings in the attic, fruit eaten on the tree.
Norway rats: the burrowers
- Look: heavier and stockier, brown, with a tail shorter than the body.
- Where they live: low. Burrows in soil, under decks and slabs, in crawlspaces and around sewers.
- How they get in: through foundation and crawlspace vents, gaps under doors and around plumbing at ground level.
- Where in Los Angeles: more common near the coast, downtown and wherever there are sewers and storm drains.
- Signs: burrows along foundations or garden beds, gnawing at ground level, droppings in the garage or crawlspace.
Why it matters
The species tells you where to seal. Roof rats mean the roofline, vents and anything touching the roof. Norway rats mean the foundation, crawlspace and ground-level gaps. Many Los Angeles homes have openings at both levels, which is why a full inspection checks the house from the roof to the crawlspace.
How small a gap they need
A rat can get through an opening of about half an inch. LA County Public Health recommends sealing gaps with quarter-inch hardware cloth or sheet metal, because rats chew through foam, plastic and caulk.
What keeps them away
- Trim branches and palm fronds back from the roof.
- Pick up fallen fruit and bring pet food in at night.
- Clear dense plants within about three feet of the house.
- Keep crawlspace and foundation vent screens intact.
More guides
This guide is general information, not a substitute for an on-site inspection. Sealwell is a referral service, not a contractor.
