Every rodent inspection is the same question: how are they getting in? Traps and bait manage the animals already inside; the entry points decide whether you're solving the problem or subscribing to it. And in Southern California, with roof rats as the main characters, the answer is usually above your head.
Read it like a rat would
Rats travel along edges — fence lines, utility wires, tree branches, the top of block walls. From any of those highways, the roofline is a menu: gable vents with chewed or missing screens, eave gaps where the roof meets the wall, tile roof edges, plumbing and AC line penetrations, and garage door corners that never quite seal.
- The quarter-inch rule: if you can fit a pencil through it, a young rat or mouse can get through it. Walk the perimeter with that gauge in mind.
- Follow the grease: rub marks along beams, pipes, and entry edges are travel receipts — they show the routes actually in use.
- Trees are bridges: branches within jumping distance of the roof get a trim recommendation every time. Six feet of clearance changes the whole equation.
- Check the attic for confirmation: droppings, tunneling in insulation, and gnawing tell you whether the entry is historic or active.
The order that works
Seal first (with materials they can't chew through — hardware cloth, metal flashing, proper sealant, never foam alone), then trap the residents you've sealed in, then monitor. Skip step one and steps two and three repeat forever. I document every entry point with photos in the service note, so the exclusion work — whoever does it — starts from a map, not a guess.