How to Get Rid of Roof Rats in San Diego

Confirm you have roof rats

Roof rats are slim and dark, with tails longer than their bodies. You rarely see them. You see what they leave behind. The county lists these signs:

• Droppings
• Gnawed fruit or nuts, and stripped tree bark
• Rub marks from greasy fur along beams, pipes and walls
• Sounds in the attic, walls or floors, mostly at night
• Gnaw marks on wood, cardboard, plastic or wires
• Piles of empty snail shells under garden plants

Rat droppings are much larger than mouse droppings, roughly half an inch or longer. If the droppings are the size of a grain of rice, you likely have mice instead. See rat droppings identification.

Take away food and cover

Roof rats move into San Diego yards for food and shelter, and both are easy to find here. Start outside:

• Pick ripe citrus and avocados, and clear fallen fruit every day during the season
• Bring pet food in at night and store it in metal or hard plastic bins
• Take bird feeders down for a few weeks, or clean up spilled seed daily
• Keep green bin and trash lids closed
• Trim palms of dead fronds and thin dense ivy, bougainvillea and hedges along fences
• Stack firewood at least 18 inches off the ground and 12 inches from fences and walls, as the county advises
• Cut back branches so nothing is within 4 feet of the roof

That last step matters most. Roof rats travel along branches, fences and utility lines to get onto the roof. Take away the bridge and many of them never reach the house.

Seal the gaps

The county's rule of thumb is to seal any opening larger than a quarter. On a typical San Diego house, check:

• The open ends of barrel tiles at the eaves, where bird stops are missing
• Gable and foundation vents with torn or loose screens
• Gaps where two rooflines meet, and where the roof meets a wall
• Openings around AC line sets, plumbing, cable and solar conduit
• The garage door seal and the side door sweep

Use hardware cloth, metal flashing, or steel or copper mesh packed tight and backed with sealant. The county's hantavirus brochure recommends 1/4 inch, 18 to 22 gauge wire mesh for repairs. Foam alone is easy for rats to chew through.

Do not seal the last gap while rats are still nesting inside, or they will chew a new hole or die in the attic. Seal most gaps, trap until catches stop, then close the last one. See steel wool vs copper mesh for materials.

Trap the rats inside

Snap traps are the standard tool for roof rats in homes. Set them in the attic along runways, where droppings and rub marks show the rats travel. Place them along walls and beams, with the trigger end facing the path. Bait with something sticky and strong-smelling, like peanut butter or a bit of dried fruit, and tie it to the trigger if rats keep stealing it.

Rats are wary of new objects, so some people leave traps unset for a night or two with bait on them, then set them. Check traps every day. Wear gloves to handle dead rats, spray them with disinfectant, and double-bag them, following the CDC cleanup steps.

California has banned most uses of second-generation anticoagulant baits since 2020 and most uses of diphacinone since 2024. Poisoned rats also tend to die in walls and attics. Traps avoid both problems. See best rat and mouse traps.

Clean up safely

Once catches stop for a week or two, clean the droppings. Do not sweep or vacuum them. The CDC says to air the space out for 30 minutes, wear gloves, spray the droppings with a solution of 1 part bleach to 9 parts water, let it soak 5 minutes, and wipe up with paper towels. Large attics with soiled insulation are better left to a crew with respirators. See attic and crawl space cleanup.

When to call a provider

Call for help if you hear rats in the attic after a week of trapping, if you cannot reach the roof safely, if the attic is too tight to move through, or if you find chewed wiring. Also call if the house backs onto a canyon, since the pressure from outside will keep testing your work. Ask for an inspection, a written list of entry points and a price for sealing as well as trapping. See rat control.

Why San Diego makes it harder

Mild weather lets roof rats breed most of the year here. Palms, fruit trees and ivy are everywhere, and the city's canyons hold large populations right behind many homes. That is why trimming and sealing matter more in San Diego than trapping alone. If your neighbors have rats too, working on the problem together, with trimming and sealing on the same weeks, gives everyone better results.