The crawl space is usually the whole story
In a lot of Seattle houses the rodent problem lives in a space the owner has never entered. A vented crawl space under a heated floor is warm on top, sheltered from 38 inches of annual rain, and lined with fiberglass insulation that tears into perfect nesting material. From a Norway rat's point of view there is no better address on the block. Getting in is easy because crawl space vents are the weakest part of most foundations. Original screens rust, get bent by a lawnmower or simply have a quarter-inch mesh gap at one corner, and rats enlarge what they find. Once under the floor they follow plumbing and duct penetrations up into wall cavities, which is how a crawl space problem becomes a kitchen problem. What to do about it is unglamorous. Every vent gets covered in hardware cloth screwed and washered rather than stapled, every pipe and duct entry gets closed, the vapor barrier gets repaired, and drainage gets fixed so the space is not holding water. Then trapping clears what is left underneath, and the follow-up counts tell you whether the seal actually held.
Roof rats in Puget Sound attics
State wildlife staff single out Puget Sound attics as roof rat territory, and anyone who has stood in a Seattle yard at dusk can see why. Laurel hedges grown into the eaves, big-leaf maples reaching over rooflines, utility lines, fences and ivy climbing a wall all work as ladders, and a roof rat will use any of them. At the top they look for the usual weak points: a gable vent with torn screening, a gap where two roof planes meet, a soffit corner that never got closed properly, a dryer or bath fan termination with a broken flap. None of these are visible from the ground, which is why a homeowner can seal a whole foundation and still hear running overhead. The access reduction matters as much as the metal. Cutting branches back several feet, stripping ivy off walls, and thinning hedges that touch the roof removes the route rather than the animal. Do the pruning first, because a rat that can no longer reach the eave has to find another building, and there is usually an easier one nearby.
A working calendar for a city with no freeze
Places with hard winters get one clean autumn spike. Seattle gets a long soft one, so the useful way to plan is around rain and daylight rather than temperature. Late summer and early fall are the repair window. The ground is as dry as it gets, crawl spaces are workable, roofs are safe to walk, and pruning can happen before the wet arrives. This is when sealing should be done, and it is also when the outdoor population starts testing buildings ahead of the rain. October through March is when complaints peak. Saturated soil pushes burrowing rats toward drier shelter under floors and into garages, and cold nights around 37F make a heated structure attractive without ever forcing a die-off outside. Spring is the discovery season. You open the shed that has been shut since October, or crawl under the house for the first time in months, and you find the droppings. That is the moment to remember the ventilate-and-wet cleanup routine rather than reaching for a broom, and to book the exclusion work while the weather still cooperates.
What a first visit should cover
A good first appointment is mostly inspection, and most of it happens in places you would not choose to go. Outside, expect a full circuit at grade: foundation vents, hose bibs, gas and electrical entries, garage and service door clearances, basement window frames, and the seams where a deck, porch or addition meets the original structure. Then the low space. Under the floor is where droppings, rub marks, footprints and shredded insulation show the actual routes, and where daylight through a gap is easy to spot from inside but invisible from the yard. Then upward: eave and soffit gaps, gable and attic vents, exhaust terminations, and any hedge, limb or cable offering a route to the roof. You should end with a punch list of openings and the material proposed for each, a trap plan with placements and a return schedule, and a clear statement of what is not included. If the visit produces a monthly price and a couple of stations by the driveway, ask what part of the building it actually changes.
Renters, landlords and shared buildings
In a converted house or a small apartment building, rodents move between units through the same crawl space, stair chase and plumbing runs that serve everyone, so a trap line in one unit usually redirects the traffic instead of ending it. If you rent, keep a record. Dated photos of droppings, notes on what time you hear activity and where, and a written request are far more effective than a phone call. Ask specifically for exclusion at the building envelope, meaning the crawl space vents, the foundation and the roofline, because that is the work a tenant cannot do and the work that ends the problem. If you own the building, the sequence saves money. Seal the shared envelope first, then trap unit by unit, then deal with the garbage and recycling area, which in Seattle is often a shared enclosure that feeds the whole population. With median home values around 850,000 dollars, a few hundred dollars of hardware cloth is cheap next to chewed wiring, wet insulation and repeat service calls across several winters.