Rats do not hibernate. Through a Puget Sound summer they live perfectly well outside on blackberry, fallen fruit, bird seed, pet food, and whatever the compost bin gives up. Then the first long cold rain arrives, usually in the last week of September, and most of those food sources go quiet at once. A heated house with a kitchen in it becomes the best address on the block.
That is why rat exterminator calls stack up across Everett, Marysville, and Lake Stevens from late September through October. Nothing changed about your house. The weather changed, and your house was already open.
The practical consequence is about timing. Exclusion work done in August is a walk-around on a dry roof. The same work in November happens in the rain, after the rats are already in the wall, and it has a trapping job attached to it. We broke the seasonal pattern down further in why rats get into Snohomish County homes every fall.
Rodent exclusion is the physical sealing of every opening a rodent can use, done with materials a rodent cannot chew back through. It is the difference between a rodent control account that quietly runs forever and one that finishes. Bait and traps are population management. Exclusion is the repair.
Four places account for nearly every entry we find on a Pacific Northwest house:
- 01
The roofline: gaps where the gutter meets the fascia, open rafter tails, lifted shingles at a valley, and gable or ridge vents with rusted screen. This is roof rat territory
- 02
Foundation penetrations: the sleeves around water, gas, electrical, and irrigation lines, plus the sill gap on older post-and-beam stock
- 03
Crawl-space vents: the screen is the first thing to go, and a torn vent is a doorway straight into the space under your floor
- 04
The utility chase: the vertical run carrying plumbing and wiring from the crawl space up to the attic. A rat that gets under the house uses it as a staircase and comes out in an upstairs wall
We seal with hardware cloth, sheet metal, mortar, and copper mesh where an opening has to stay ventilated. Expanding foam on its own is not exclusion, it is an afternoon's work for a rat. If the crawl space is the entry point and the barrier under there is already torn up, the sealing usually rides along with crawl space cleanout and vapor barrier replacement so the space gets closed and cleared in one trip instead of two.
A quarter inch is the number because that is what a house mouse fits through, and Washington's Department of Health uses the same figure in its rodent-proofing guidance. A rat needs closer to a half inch, but we survey to the smaller measure, because sealing to rat size on a house that also has mice just means you will be calling a mouse exterminator in the spring.
The survey runs the building elevation by elevation, north wall through west wall, then the roof plane, then the crawl space from the inside. Every opening gets photographed and located before anything gets sealed, so what you approve is a list rather than a promise.
Before anyone starts work, the scope you are handed should name:
- 01
Each opening by elevation and height, not just a count
- 02
What material closes it, and why that material for that gap
- 03
Which openings have to stay ventilated and get screened rather than filled
- 04
What is out of scope, including roofing, siding, and framing repair we are not the trade for
- 05
Whether the crawl space needs clean-out before sealing, because sealing contamination in is worse than leaving it open
If a scope does not list openings, nobody has surveyed the house yet. Every job here is quoted after that inspection, and you can ask us for a rodent inspection before you commit to anything.
What you hear at two in the morning tells us more than you would think. Scratching that travels horizontally across the ceiling and then stops is almost always a roof rat running a joist bay in the attic. A heavier thump with a drag to it is a rat in a wall cavity between studs. Fast, light, ticking activity that stays low near the floor in short bursts is a mouse.
Rats do not wander a wall at random. They run cavities the way you use a hallway, and the route is fixed: the utility chase up from the crawl space, along the stud bay behind the plumbing wall, out at the top plate into the attic. So when people ask how exterminators get rid of rats in walls, that is the answer. We do not open the wall. We find both ends of the run, seal the top plate and the chase, and set traps in the runway the rat is already using.
Cutting drywall is a last resort and it is almost never the faster route. The rat already has a way out. Take away the way in, put the trap on the road it uses every night, and it comes to you.
Three animals, three working heights, three fixes. Getting the identification right before anyone seals anything is what keeps you from closing up the foundation while the problem is coming in over the gutter. Here is what separates them:
- 01
Roof rats are the climbers: slim body, long tail, big ears. They enter high, nest high, and around Edmonds, Lynnwood, and Lake Stevens they are the most common rat call we get. Fix the roofline first
- 02
Norway rats are the burrowers: heavy body, blunt nose, short tail. They come in low through foundation gaps and crawl-space vents, and burrow under sheds and slabs. Fix the ground plane and the vents
- 03
House mice need a quarter-inch gap and a garage door that does not quite seal. A mouse exterminator job is rarely one mouse, and it almost always includes the garage
- 04
Deer mice turn up in detached garages and outbuildings more than in houses, and they are the hantavirus carrier in Washington, which changes how the cleanup gets handled
This is also why rat removal and mouse control get handled off one inspection rather than two. Most houses that have one have the conditions for the other, and the gap survey is the same walk either way.
Order matters more than product. Seal first, then trap. A house that is still open is a house that refills, and trapping into an open house is how rodent removal turns into a subscription nobody meant to buy.
Once the building is closed, trapping is fast and it is finite. Snap traps go in confirmed runways, on the greasy rub marks and along the joist bays where the droppings already are, never scattered on a guess. We check them, remove what we catch, and reset. Most homes go quiet inside a couple of weeks.
We do not close a job on one empty check. Two consecutive checks with nothing in the traps and no fresh droppings is the bar, and if activity comes back inside your warranty window we are out within 48 hours at no charge. What a rodent exterminator is really selling is the verification, not the trap.
Rodents leave far more behind than they weigh. A season under the floor means droppings through the vapor barrier, urine staining, insulation pulled down and shredded for nesting, and sometimes a carcass in a wall you smell before you find. If you have not been under there yet, the signs of rats in a crawl space are worth knowing before you open the hatch.
Do not sweep it and do not run a shop vac over it. Washington's Department of Health is direct about this, and so are we: dry sweeping and vacuuming stir contaminated dust into the air you are standing in. The state's guidance is to open the space up and air it out for at least 30 minutes, wet the material down with a 10 percent bleach solution instead of dry-brushing it, then bag it. Deer mice are the hantavirus carrier in Washington, and hantavirus is rare but it is not worth gambling a Saturday on.
In a crawl space that has been lived in, the barrier itself is usually the thing that has to go. That is a haul-out rather than a wipe-down, and it is the point where rodent work and crawl space vapor barrier replacement become one job.
Sealing a house does not take the pressure off it. The greenbelt behind the fence, the neighbor's bird feeder, and the blackberry along the alley are all still there, and rodent pressure in the PNW never really drops to zero because the winters are mild. That is what recurring rodent pest control is for.
Tamper-resistant bait stations sit around the exterior, locked, anchored, and keyed so only a rodent reaches what is inside. Nothing loose, nothing indoors, nothing a dog or a kid can get into. On recurring service we refill and re-check every station on every visit, which is the part that separates a station that works from a station that is decoration. A bait box dropped once and never opened again is an empty plastic box.
The interval most homes here settle into is quarterly, with the fall visit weighted heaviest because that is when the population moves. Homes backing onto a greenbelt or a creek line, and anything with a history of roof rats, usually run bi-monthly through the wet season. We cover the same interval on every route we run, including rodent control in Everett and the rest of the north sound.
