Rodent Exclusion: Sealing Rats Out, in the Order That Works
Trapping ends the rats you have. Sealing ends the ones you'd have next month — but only if it happens in that order. Here's the seal-up I do on San Gabriel Valley houses: the openings I close, the material I close them with, what the one-year warranty actually covers, and why fall is the month this visit is worth the most.
ExterMetro seals rodents out of San Gabriel Valley homes in the order that works: trap the animals already inside, then close every entry point with metal and mesh, with attic droppings cleanup where it's needed and a one-year written warranty. Owner-led from Arcadia. CA SPCB Reg. #8828 · (626) 409-1584.
Why the Order Matters: Trap First, Then Seal
Exclusion means physically closing the openings a rodent uses to get into a building. It's the half of rodent work that actually changes the outcome — but only if it happens second.
Here's the job I get called out to fix. Somebody spends a Saturday on a ladder, finds six gaps, and closes all six. What they've built isn't a sealed house; it's a sealed-in colony. Rats that can't get out do one of two things: they chew a new exit, usually somewhere worse than the one you closed, or they die in a wall void and you learn about it a week later through the smell. Bait ends the same way, one step slower — which is why I don't reach for rodenticide as a matter of course, and why California has pulled back hard on the strongest ones after what they did to the owls and hawks that eat poisoned rats.
So the sequence is fixed, and on my jobs it isn't negotiable:
- Inspect. I walk the roofline, eaves, vents, utility penetrations, garage and crawl space access, and map every opening — not the first one. All of them.
- Trap. Snap traps set in the runs the animals are actually using, checked and reset until the catch goes to zero and stays there. This stage has to finish before the next one starts.
- Seal. Every mapped opening closed with material a rodent can't chew through.
- Verify. I come back up and re-walk the list with you, because a seal-up you've seen is a seal-up you can hold me to.
Trapping without sealing is a subscription — the yard keeps sending replacements. Sealing without trapping is a mistake you can smell. Run in that order, it's the fix that holds. If what brought you here is scratching over the bedroom ceiling, start there; the broader service is rodent control.
What I Actually Seal: The Openings, Top Down
Our rat is the roof rat, and it's a climber, so I inspect a house the way the rat approaches it — from the top down. The gap it needs is about the size of a quarter. A mouse needs about the width of a dime.
Up high, the recurring offenders are attic vents with screens gone rusted, torn, or chewed open at a corner; roof returns, that open pocket where an eave dies into the roof edge, which framers left unclosed on a lot of the older housing stock here; and lifted tile edges, where the wavy first course of an S-tile roof leaves half-moon channels aimed straight into the attic. Before any of that, though, I look at the trees. A citrus or ficus limb resting on the roof is an on-ramp, and ivy on a block wall is a ladder that gets climbed every night.
Down low it's simpler and easier to find: the garage door, whose bottom corners flare with age until you can see daylight from inside with the door shut; the stucco penetrations where cable, gas, AC and irrigation lines were drilled generously and never closed; foundation vents with bent or missing screens; and the pet door that swings free all night.
If you want the full walk-through — what each one looks like from a ladder, and the dusk walk-around you can do yourself before you call anybody — I wrote it up separately: the entry points I check first.
What I Seal With, and Why It's Metal Instead of Foam
This is what separates a seal-up that holds from one that gets reopened in November, and it's almost entirely material choice. A rat's incisors grow continuously and it gnaws to manage them. Anything softer than its teeth isn't a barrier — it's a speed bump.
What doesn't hold: expanding spray foam, which a rat chews through in a night and which mostly succeeds at hiding the hole from the next person who looks. Window screen and fiberglass mesh, built to stop insects and torn like paper. Steel wool, which packs beautifully and then rusts out and drops. Caulk on its own, with nothing structural behind it. Plastic vent covers. And every repellent on the shelf — ultrasonic plugs, peppermint, mothballs. In twelve years I've never once opened an attic and found a repellent had done anything.
What does hold is metal, cut to the opening and fastened, with sealant finishing the joint rather than doing the work:
| Opening | What I usually find | What closes it |
|---|---|---|
| Attic vents | Screen torn, rusted through, or chewed at a corner | Heavy galvanized hardware cloth, secured at the edges — not window mesh |
| Roof returns | Open pocket where the eave meets the roof edge | Sheet metal cut to the pocket and fastened down |
| Lifted tile edges | Half-moon channels under the first course of S-tile | Formed eave closures fitted under the tile |
| Garage door corners | Daylight at the bottom corners of a closed door | New bottom seal plus metal corner guards |
| Pipe and cable penetrations | Oversized holes around lines through the stucco | Packed with metal mesh, then sealed over |
| Foundation and crawl vents | Bent, rusted, or missing screens | Sturdy new screen in a fastened frame |
| Pet doors | A flap swinging free all night | A locking cover after dark — a habit, not hardware |
None of it is exotic. It's ordinary hardware-store material used correctly, in every opening rather than the obvious three, by somebody who's been up on enough valley rooflines to know where the fourth one is.
The Fall Seal-Up: Why September and October Are the Ones That Count
You can seal a house any month of the year and it works. But there's one window where the same work is worth more, and here it runs roughly from Labor Day to the first real rain.
The pattern is the same every year. Through summer, rodents live outside and do fine — the yard has fruit, water and cover, and there's no reason to be in your attic. Then the nights cool, the fruit drops and gets cleaned up, the first storm soaks the ivy and the wash, and the whole population starts testing structures for somewhere warm and dry. September is when they begin pushing in. October and November are when they're already in. That's the entire calendar behind the line on my pest calendar: the fall seal-up is the single highest-value pest visit of the year.
The value is in the timing, not the work. A house sealed in September never hosts them — no nesting in the insulation, no chewed wiring, no droppings to clean out of the attic, no scratching over the bedroom at 2am. The identical job in December is remedial: now there's a population inside that has to be trapped out first, and there's usually cleanup on the other side. Same ladder, same metal, a much bigger job.
If you've already heard something overhead, this isn't a seal-up call yet — that's a trap-first call, and the sealing is stage three. If you've heard nothing and you're near the foothills, the canyon mouths or the river wash, this is the month.
Send me a photo of the roofline or the vent you're worried about and I'll tell you what I'm looking at. Quotes are free, in person or from photos.
Droppings, Nesting and the Attic Cleanup
If rodents have been living up there, sealing the house doesn't finish the job — there's material left behind. Insulation gets matted and soiled, nesting gets built into corners and stored boxes, and droppings collect along the runs.
Removal and disinfection of droppings and nesting is part of my rodent work, handled with professional disinfectants and proper protective methods, in the attics, garages and storage areas where it actually accumulates. Whether your job needs it depends entirely on how long they were in and how much they left.
One rule before you go up there with a broom: don't sweep or vacuum rodent droppings dry. Ventilate the space, keep people and pets out of it, and read the hantavirus page first — it explains exactly why dry sweeping is the wrong move and what to do instead. That page exists so I don't have to re-explain it here, and it's worth the four minutes.
What the One-Year Warranty Covers, and What Exclusion Can't Promise
Rodent work I do carries a one-year warranty, terms in writing before the work starts, the same way my termite side works. If rodents get back in through something I sealed inside that year, I come back and deal with it.
Now the honest part, because a seal-up is easy to oversell and I'd rather you hear the limits from me than discover them.
A house isn't a sealed box, and nobody can make it one. What I can do is close every opening I can find and reach, with material that holds, and re-walk the finished work with you. What I can't do is promise that a building with a roof, vents, a garage and utility lines running through its walls will never present a new opening. Stucco cracks. Tile shifts. A trencher opens a line. A roofer lifts a course and sets it back a quarter-inch high. Trees grow back into the roofline. All of that is ordinary building behavior, and any of it can create a doorway that wasn't there when I left.
That's exactly why the coverage is a year rather than an open-ended promise. What exclusion does is take a house that was being entered and stop it from being entered — and leave you a documented record of what got closed, so next year's question is "has anything changed?" instead of "where do we even start?"
The maintenance that keeps it holding is short, and most of it is yours: keep limbs and vines cut back off the roof, pick up fallen fruit, don't leave pet food out overnight, and once a season close the garage door, kill the lights and check the bottom corners for daylight. If you'd rather I look at it on a schedule, say so and we'll set one.
When Exclusion Is the Right Call, and When It Isn't
Exclusion is the right call when the animals are rats or mice and the structure is the problem — you're hearing them overhead, finding droppings in the garage, or you live somewhere the yearly push is a certainty and you'd rather get in front of it than behind it.
It's the wrong call, or at least the wrong first call, in a few specific situations, and I'll tell you so instead of selling you a seal-up:
- Something is up there right now. Then we trap first. Sealing an occupied attic is the mistake this whole page is about.
- The noise happens in daylight. Daytime rolling and thumping is usually squirrels; daytime chirping in a vent is usually birds. Those are wildlife-removal jobs, not exterminator jobs. Sending you to the right trade costs me a sale and spares you a month.
- It's a shared wall in a condo or an attached unit. I can seal your envelope, but if the building is connected and the neighbor's side is open, the honest answer involves the association — that's a community property conversation.
- You've got a raccoon or an opossum. Same as squirrels: bigger animal, different trade.
Everything else — roof rats, Norway rats, house mice, in a single-family structure — is squarely my work, and it's the same sequence every time. Not sure which one you've got? The rat and mouse ID guide sorts it in about a minute, or send me a photo and I'll sort it for you.
Ready to get it on the calendar before the nights cool off? Call (626) 409-1584, text me a photo, or book online — either way it goes to me, not a call center.
Quick Answers
Quick Answers.
What is rodent exclusion?
Rodent exclusion is the structural half of rodent control: physically closing every opening a rat or mouse uses to get into a building, with material they can't chew through. Trapping removes the animals already inside; exclusion is what stops the next ones from following them in. On my jobs the two go together in a fixed order — trap until the activity stops, then seal, then come back and verify.
Should I seal the holes before or after trapping?
After. Sealing an occupied house shuts the animals in, and rats that can't get out will chew a new exit somewhere worse or die in a wall void where nobody can reach them. Trap until the catch goes to zero and stays there, then seal every opening, then verify. That order isn't a preference — reversing it is the single most common rodent mistake I get called out to fix.
What is a fall seal-up?
It's exclusion done before the seasonal push instead of after it. In the San Gabriel Valley rodents start testing structures in September as the nights cool, and they're established indoors by November. A house sealed in early fall never hosts them, so there's no trapping stage and no attic cleanup afterward. The identical work in December is remedial. That timing is why the fall seal-up is the highest-value pest visit of the year.
Can you really seal every hole in a house?
I can find and close every opening an inspection reaches, and I re-walk the finished work with you — but no honest company can tell you a house becomes a sealed box. Stucco cracks, tile shifts, trades drill new penetrations, and limbs grow back into the roofline. What exclusion does is take a house that was being entered and stop it from being entered, with a written record of what got closed. That's why the work carries a one-year warranty rather than an open-ended promise.
What materials do you use to seal rodent entry points?
Metal, cut to the opening and fastened: galvanized hardware cloth over vents, sheet metal at open roof returns, formed closures under lifted tile, metal mesh packed into oversized pipe and cable penetrations, and a new bottom seal with corner guards at the garage door. Sealant finishes the joint; it never does the structural work. The test is simple — if a rodent's teeth can go through it, it isn't a barrier.
Will spray foam or steel wool keep rats out?
No. A rat chews through expanding foam in a night, and steel wool packs well but rusts out and drops loose. Both mostly succeed at hiding the hole from the next person who inspects it. Window screen and fiberglass mesh are built to stop insects and tear easily. These openings need metal that's cut to fit and fastened down.
How much does a rodent seal-up cost?
It's priced by the house, not off a menu. What moves it is the size and construction of the structure, how many openings there are, how reachable the roofline is, and whether the attic needs cleanup once the activity stops. Quotes are free — in person, or from photos you text me — and you get the number in writing before anything starts.
Is the exclusion work covered by a warranty?
Yes — rodent work carries a one-year warranty, with the terms in writing before the work begins. If rodents get back in through something I sealed during that year, I come back and handle it. My termite work carries two years; rodent work is one, and I'd rather give you the real number than round it up.
Do you use poison as part of a seal-up?
Not as a matter of course. A baited rat usually dies inside a wall void or under insulation where nobody can reach it, and the odor lasts weeks. It also does nothing about the openings, so the next family walks in the same way. California has restricted the strongest rodenticides with good reason — they move up the food chain into owls, hawks and pets. I trap, and then I seal.
What about the droppings and nesting in the attic?
Removal and disinfection of droppings and nesting material is part of the rodent work where it's needed, handled with professional disinfectants and proper protective methods. Don't sweep or vacuum droppings dry yourself — ventilate the space, keep people and pets out, and read the hantavirus guide before you touch anything up there.
My house is newer. Do I still need exclusion?
Often, yes. New construction still has vents, roof returns, utility penetrations and a garage door, and those are the openings rodents use. What newer homes usually lack is the deteriorated screen and flared garage seal that make an older house obvious, so the gaps are fewer and smaller and the seal-up is a shorter job. Homes against the foothills, the canyon mouths or the river wash see pressure regardless of build year.
How long does a seal-up take?
On most single-family homes the sealing itself is a day's work once trapping has finished. The trapping stage ahead of it runs as long as it needs to — until the catch stops — because sealing early is what causes the problems this whole page is about. You'll get the shape of the schedule with the quote, so there are no surprises.
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