Why roof rats own the attics in San Diego
The roof rat is built for this coast. It is lighter and longer-tailed than a Norway rat, it climbs well, and it prefers to nest above ground rather than dig. In a neighborhood of mature palms, walls covered in bougainvillea and fruit trees in half the yards, everything it needs is stacked vertically. The route rarely varies. The animal climbs a trunk, a vine or a utility line to the roof, then works the edge looking for a way in. That way in is a soffit gap, a gable vent with rusted screening, a lifted shingle course at a valley, or a plumbing vent boot gone brittle in the sun. Inside it finds insulation to nest in, no predators, and top plates that lead to every room in the house. So the work belongs at the roofline. Traps in the kitchen catch nothing when the animals never come down that far, and a ground-level bait station answers a question the rat is not asking. Trim the bridges, screen the vents in metal, close the fascia gaps, and the route stops existing.
What the state's bait restrictions change about your plan
If you pictured a technician arriving with bait boxes and calling it finished, the plan looks different in California. UC IPM lists the prohibition on most uses of second- and first-generation anticoagulants, which takes brodifacoum, bromadiolone, difethialone, diphacinone, chlorophacinone and warfarin off the table in most areas. Bromethalin, cholecalciferol and zinc phosphide remain, with their own constraints. What replaces them across San Diego is mechanical: snap traps set in numbers, checked on a schedule, moved based on what catches. Slower for a couple of days, better for everything after. You get a count of animals removed rather than a guess, nothing dies inside a wall cavity you cannot open, and there is no secondary risk to the hawks, owls and cats that eat rodents. Use this when you compare bids. A company leading with exclusion and trapping is working the way both the rules and the biology point. One leading with bait volume is either behind on the regulations or selling a recurring visit that never closes the entry.
In a 10-inch rainfall climate, follow the water
San Diego gets around 10 inches of rain in an average year, and almost all of it lands in a handful of winter months. For most of the calendar, the only dependable water on a residential block is water somebody put there. That changes where you look. Drip irrigation running at dusk, a weeping hose bib, condensate off an air handler, a pet bowl left out overnight, a pool filter that seeps, the saucer under a potted lemon: each is a small reliable supply, and rat activity clusters around them. Norway rats especially will burrow within a short walk of a drink, so a line of holes in a planter bed usually points at an emitter leaking a few feet away. House mice are the exception worth knowing. They take most of what they need from food and can go a long time without free water, which is why a pantry mouse problem does not answer to the same logic. For rats, though, walking the irrigation at dusk with a flashlight is twenty of the most productive minutes available to you, and it costs nothing.
What a first inspection should actually produce
You are buying a diagnosis, so judge the visit by what you hold at the end of it. Someone should get into the attic and the crawl space or slab perimeter rather than only walking the interior, looking for rub marks, droppings on top plates, disturbed insulation, chew damage on wiring, and daylight at the eave. Outside, the walk should cover the full roof edge, every vent and vent boot, the penetrations where cable and refrigerant lines enter, the garage door seal, the weep screed along the stucco, and any burrows in planter beds. Where a lot has a detached garage or a casita, each building earns its own list, because sealing the house alone just moves the colony forty feet. The deliverable is a numbered list of openings with a material proposed for each, a species call with the evidence behind it, a trapping schedule with a visit count, and a plain yes or no on attic cleanup. A company that will not put that in writing before quoting is asking you to buy a number instead of a plan.
Renters, landlords and who pays for the sealing
With a median home value around $880,000, a large share of San Diego rents, and rodent duties split fairly predictably. Closing openings in the building envelope is a structural repair, which normally belongs to the owner. Sealed food containers, taken-out trash and no cardboard stacked against a wall belong to whoever lives there. Document from day one. Photograph droppings with something for scale, write down the dates and times you hear activity, and report it by email or through the management portal rather than a phone call nobody logs. If the building is a duplex, a fourplex or a stacked condo, say so, because rodents move through shared walls and utility chases and a single-unit fix seldom holds. For small landlords the arithmetic favors sealing once and doing it right. Recurring trapping with no exclusion is a bill that returns every year, and insulation contaminated over three or four seasons eventually costs several times what metal work at the eave would have.