Rodent exclusion
Why We Seal Out Rodents Before Installing New Insulation
New insulation in an attic rats can still reach gets ruined fast. Here's how we clean, sanitize, seal and monitor an LA attic, and why we wait 12–15 days before insulating.
Short answer: if rodents can still get into your attic, new insulation becomes their new nest. So we clean the attic out, sanitize it, air seal it and rodent-proof it first. When rodents are active, we check back over about two weeks and only install insulation once we're sure the attic is secure, typically 12–15 days.
What goes wrong when you insulate first
Fresh insulation is warm, soft and easy to tunnel through. If a single roof rat is still inside, or the gap it came through is still open, it will move into the new layer within days. You end up with the same droppings and odor problem, plus a second insulation bill.
That's why the order of the work matters more than any single product.
Our process, step by step
1. Inspect and photograph
We go through the attic, crawlspace and roofline and photograph droppings trails, nests, damaged insulation and every gap we find. You see the photos before we recommend anything.
2. Thorough cleanup and insulation removal
We remove the old insulation, droppings and nesting material with a large industrial vacuum. The hose runs from the attic to bags outside, so nothing comes through the house.
3. Sanitize
With the attic bare, we sanitize the framing and attic floor to deal with odor, urine and bacteria.
4. Air seal and ventilate
An empty attic is the best time to seal the gaps between your living space and the attic: top plates, wiring and plumbing holes, can lights. Where an attic runs hot, we add solar attic fans to pull the heat out.
5. Rodent-proof and monitor (when rodents are active)
We rodent-proof the attic and crawlspace by closing every vent, gap and roof or pipe penetration so rodents can't come and go, and any still inside are trapped. Then we come back on periodic visits to check for activity. We only move on once we're certain the attic is secure, typically after 12–15 days.
6. Install fresh insulation
Blown-in or batts, to your target R-value and Title 24 compliant. If your home qualifies for a utility rebate, we file it.
Where rodents usually get in on LA homes
- Gaps around roof vents, roof edges and where different rooflines meet
- Openings around pipes, wires and A/C lines going into the house
- Damaged or missing screens on attic and foundation vents
- Gaps under eaves and around the garage
Rats can get through an opening about the size of a quarter, so exclusion means finding and closing all of them, not just the biggest one.
Signs you have rodents in the attic
- Scratching or running sounds in the ceiling at night
- Droppings in the attic, garage or storage areas
- A stale, musky smell that gets worse on hot days
- Tunnels or flattened trails in the insulation
Want to see our full process? It's on our Westside Attic Reset page.
Common questions
How long after rodent proofing can I install new insulation?
When rodents are active, we typically wait 12 to 15 days after sealing the attic and crawlspace, with periodic visits in between, and only insulate once we're certain the attic is secure.
Can I just add new insulation on top of the old, contaminated insulation?
We don't recommend it. Droppings, urine and nesting material stay underneath, the smell stays, and rodents that are still getting in will simply move into the new layer.
How small a gap can a rat get through?
Rats can squeeze through openings roughly the size of a quarter, and mice through even smaller gaps. That's why exclusion means closing every vent, gap and roof or pipe penetration, not just the obvious holes.