Crawlspace Repair & Rodent Exclusion, San Juan Island

This is the most under-served job in the San Juans and it is not close. Every house here has a crawlspace or a low basement, most of them are wood-framed and cedar-sided, a large share of them sit empty for six to ten months a year, and the county is full of deer mice, roof rats in the more settled areas, and squirrels that treat a soffit as a door. An empty house on Waldron or Decatur in October is a heated, dry, undefended cavity with nobody in it. The rodents are not making a mistake.

Trapping is a separate trade and a separate service. What I do is exclusion, which is the part almost nobody does properly: physically closing every opening a rodent can use, in materials they cannot chew through, and then repairing the damage they already did. If you trap without excluding, you have signed up for trapping forever. If you exclude properly, the population inside collapses because nothing new gets in.

The survey is the real work. A mouse needs a gap the width of your little finger, a rat needs about an inch, and island houses hand them dozens. Foundation vent screens are the classic — galvanized mesh that has rusted through in salt air, or the original quarter-inch hardware cloth that a rat simply widened. Crawlspace access hatches with a warped plywood door and no gasket. The gap where a cedar base course meets the foundation and the shingles have curled away. Cut siding around a hose bib, a dryer vent, or a cable penetration where nobody backfilled the hole. Rim joist gaps behind the siding. Soffit and gable vent screens that a squirrel opened. Open eave blocking on older cabins. Chimney chases. Under a deck where the ledger meets the wall and nobody could see the framing. And the roof, which matters more here than people expect, because a fir or madrona limb overhanging a roof is a rodent bridge and the branch is the actual entry point.

Sealing has to be done in materials that hold. Stainless or galvanized hardware cloth over vents, mechanically fastened, not stapled loosely and painted. Sheet metal or hardware cloth backing behind foam where a gap has to be filled — expanding foam alone is a rodent snack. New solid, gasketed, latching crawlspace access doors. Copper mesh packed into irregular masonry gaps. Proper flashing and trim closures where wood has moved. Rodent-rated door sweeps on garage and outbuilding doors, because a garage is usually the first room they take.

Then there is the inside of the crawlspace, which is where the money is. Under a house that has had a rodent population for two or three seasons you typically find batt insulation pulled down out of the floor bays and nested in, a vapor barrier shredded and dragged around, contaminated nesting material, and sometimes chewed ducting. All of that is repairable carpentry and materials work: haul out the ruined insulation and barrier, put down new sheeting, re-support and reinstall floor insulation with proper stays, and re-block where the framing allows. A crawlspace with a clean, continuous vapor barrier and dry, supported insulation is also just a better crawlspace for island humidity, which swings hard here and is what makes floors cold and doors stick in the first place.

Two limits, both firm. Chewed wiring is an electrician. I hold a Washington general contractor registration, not an electrical or plumbing license, so if a rodent has been into conductors I stop, photograph it, and get a licensed electrical contractor out — and I will tell you plainly that this is the failure mode that burns island houses down. Same for any supply line or drain a rodent has damaged: that is a licensed plumber. I do the openings, the screening, the barrier, the insulation, and the framing repairs, and I coordinate the rest.

You get photographs of everything, which is the only way any of this is verifiable from off-island. Every entry point found, every one sealed, the crawlspace before and after. That set is also what makes the difference at sale time, because a buyer’s inspector will go into that crawlspace and a documented exclusion is a far better answer than a bucket of traps.

For a house that sits empty, exclusion is the one-time fix and a scheduled look is the maintenance. Screens rust in salt air, wood moves, and a new limb grows over the roof every few years. That is exactly the kind of thing a property care visit exists to catch in month two rather than in year three.