How California's rodenticide rules changed the job in San Francisco
For years the standard first move on a rat call was a ring of bait stations. California's prohibition on most first and second generation anticoagulants, described by UC IPM, took that off the table for most situations. Brodifacoum, bromadiolone, difethialone, diphacinone, chlorophacinone and warfarin cannot be applied in most areas, and the remaining options, bromethalin, cholecalciferol and zinc phosphide, are not a drop-in replacement. The practical result is that a competent San Francisco plan looks like construction work with traps attached. Someone walks the roofline and the foundation, lists the openings, and closes them with metal, then traps out what is stuck inside and comes back to confirm the count fell to zero. That is slower and more physical than a bait route, and it is better. Bait never fixed the hole; it just intercepted animals on their way through. It also carried real risk to dogs, cats and the hawks and owls that catch a poisoned rat. If a provider quotes you a monthly station service and nothing else, ask what the plan does to the building itself, because in this state that is where the result comes from.
Roof rats overhead, Norway rats underneath
The single most useful thing you can work out early is which animal you have, because the two rats in San Francisco use opposite halves of the building. Roof rats climb. Fences, cables, downspouts, ivy on a wall and any branch within a few feet of the eave are all ladders, and once at the top a chewed vent screen, a soffit gap or a junction between roof planes is enough. They nest above ceilings, which is why so many calls start with running noises overhead after dark. They also raid fruit trees, so stripped fruit in a back garden is a decent early warning. Norway rats are heavier and stay low. They dig burrows two to three inches across in soft ground against a foundation, under a deck or beside a garage slab, and they come in at grade, often under a door with more than a half-inch clearance. In a wet winter with 24 inches of rain arriving over a few months, saturated ground pushes them toward drier crawl spaces and basement garages. A plan that only addresses one height leaves the other route open.
Shared walls, flats and who is responsible
In a city where much of the housing is stacked or attached, a rodent problem is rarely confined to the unit that reports it. Animals travel between flats through plumbing chases, shared basements, garage ceilings and the light wells that serve several units, so trapping in one apartment often just moves the traffic next door. If you rent, the use is documentation. Photograph droppings and gnaw damage with dates, put your request in writing, and ask specifically for exclusion at the building envelope rather than another round of traps inside your unit. Note where you hear activity and at what time, since that helps a crew find the runway. If you own or manage the building, the sequencing matters. Seal the shared envelope first, then trap unit by unit, then check the trash and recycling area, which in San Francisco is often an alley or a garage bay serving several buildings at once. With median home values around 1.3 million dollars, the sealing work is small relative to what chewed wiring and ruined insulation cost to put right across multiple units.
What to expect on the first inspection
A useful first visit spends most of its time on ladders and in tight spaces, not standing in your kitchen. Outside, the circuit should cover the foundation, hose bibs, gas and electric penetrations, garage and service door clearances, basement window frames, and any point where a deck, stair or addition meets the original wall. Then upward, which is the half people skip: eave and soffit gaps, attic and gable vents, dryer and bath exhaust terminations, roof plane junctions, and any tree limb, cable or vine offering a route to the top of the building. Inside, the attic and crawl space carry the evidence. Droppings, rub marks, flattened insulation and urine staining show where animals travel and roughly how long they have been there. You should end up with a list of specific openings and the material proposed for each, a trap plan with locations and a follow-up schedule, and a clear line between what is included and what is extra. A one-page price with no punch list is not an inspection result.
A twelve-month rhythm instead of a season
Cities with hard winters get a clear autumn spike. San Francisco does not, and planning as though it does is how buildings stay infested. With summer highs around 67F and winter lows near 46F, nothing forces a population crash, so the useful calendar is about weather rather than temperature. The rain window is the pressure point. As storms saturate the ground, burrowing rats look for drier shelter, and that is when garages, crawl spaces and basement storage start producing droppings. Doing your sealing before the first significant rain is worth more than doing it in January with water running past the foundation. The drier months are the working window. Metal work goes in more easily, roofs are safer to walk, and yard access is better for cutting limbs and pulling ivy off walls. Throughout, the maintenance habit UC IPM recommends is periodic checking. Twice a year, walk the perimeter and look up at the eave line, then look down at door clearances. Most reinfestations begin at an opening that was fine last time you looked.