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How to Get Rid of Squirrels Under a Deck

A one-way door and a buried L-footer in hardware cloth. The exclusion sequence, the two months when sealing kills young, and the mesh spec that holds.

By Salma 4 min read Save to Pinterest — opens Pinterest in a new tab
A squirrel foraging at ground level in a daisy-studded lawn
Photo: Ralphs_Fotos, Pixabay Content License, via Pixabay
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The sequence is one-way door first, permanent screen second. Trapping on its own fails, because the space under the deck is what attracted the squirrel — remove one and another arrives.

Step 1: work out what is under there, and when

Squirrels under a deck are usually using it as a den or a cache store rather than a nest, but not always.

  • Listen at dawn and dusk — squirrels are diurnal, so daytime activity fits. Night noise points to a skunk, raccoon or flying squirrel instead
  • Look for the entrance — a worn hole at the base of the skirting, often at a corner or where the ground has eroded
  • Check for more than one. There almost always is
  • Note the season. Roughly February to April and August to October are the litter windows

The timing matters more than anything else here

Sealing a deck with unweaned kits inside walls them in. They die in the cavity, and resolving that means lifting decking. If you find young, wait seven to eight weeks from birth until they are moving in and out on their own.

Step 2: make the space unattractive

While you prepare the exclusion, cheap pressure helps the animals decide to leave:

  • A work light shone into the cavity
  • A radio on talk programming, left running
  • Opening up the skirting on one side so it stops feeling enclosed
  • Removing the food. Clear spilled birdseed and fallen fruit, and secure bins

None of these is a solution. They tilt the odds while you fit the door.

Step 3: the one-way exclusion door

A one-way door is a hinged flap or a wire cone fitted over the main entrance that lets an animal push out and not back in.

  1. Screen every other opening first with hardware cloth, so there is one way out
  2. Fit the door over the remaining entrance, firmly, with no gap round the edge
  3. Leave it three to five days — longer in cold weather, when squirrels stay in more
  4. Watch for activity around the flap

Step 4: verify it is empty

Do this even after the door has been in place, because an unfound second entrance is the usual reason a sealed deck still has a squirrel in it.

  • Stuff the entrance loosely with crumpled newspaper. Leave it two to three days. Undisturbed means nothing is passing
  • Dust flour at the opening and look for tracks
  • Listen again at dawn and dusk

Step 5: screen it permanently

elementspec
Meshhalf-inch galvanised hardware cloth, 19 gauge or heavier
Fixingscrewed to the deck frame with washers, not stapled to the skirt alone
Below grounddown 8–12 in, then turned outward 12 in just under the soil
Cornersoverlapped and wired together, not butted
Accessleave one screwed panel you can remove, for future maintenance

The outward L is the part people skip. Squirrels, like rabbits and groundhogs, dig at the point of resistance and follow it down — a barrier that goes straight down just tells them how deep to go. A horizontal apron is what stops it, because there is no cue to back off a foot and start again.

What does not work

  • Mothballs and ammonia rags — a pesticide and a folk remedy respectively; one is illegal used this way, the other does nothing
  • Ultrasonic devices — no reliable evidence
  • Trapping as the whole plan — legal in some places and not others, relocation often prohibited, and the vacancy refills
  • Poison — not legal for squirrels in many jurisdictions, and it kills what eats the carcass
  • Filling the hole and hoping — reopened within a day

Afterwards

Fix what made the space attractive: regrade the soil so water does not scour a gap under the skirt, replace rotten skirting boards, and keep the perimeter clear of leaf litter and stacked material. A deck that is dry, lit at the edges and screened properly stops being a den site.

Common questions

How do I get squirrels out from under my deck?

Fit a one-way exclusion door over the main entrance so the animals can leave but not return, leave it in place for several days, then permanently screen the whole perimeter with half-inch hardware cloth buried in an L-shape. Trapping alone does not hold, because the space stays attractive and another squirrel moves in. The exclusion plus the screen is what ends it.

When should I not seal under a deck?

Roughly February to April and August to October, the two periods when squirrels have unweaned young. Sealing then traps kits that cannot leave, and they die in the cavity — which becomes a smell problem you have to dismantle decking to resolve. If you find a nest with young, wait until they are mobile and leaving on their own, usually seven to eight weeks after birth.

What mesh keeps squirrels out from under a deck?

Half-inch galvanised hardware cloth, 19 gauge or heavier. Chicken wire is too soft — squirrels chew through it and the thin galvanising rots where it is buried. The mesh needs to run from the deck frame down into the ground and then turn outward in an L about 12 inches wide just under the soil surface, because squirrels dig at the base of a barrier rather than backing off from it.

Will mothballs or ammonia drive squirrels out from under a deck?

No. Mothballs are a registered pesticide and using them this way is illegal in many jurisdictions as well as hazardous to children and pets. Ammonia-soaked rags are sometimes suggested and rarely work. What does shift a squirrel short-term is light, noise and a radio in the cavity — enough to make it unattractive while you fit the exclusion door, not enough to be a solution on its own.

Is it legal to trap squirrels?

It varies by region and by species, and relocating trapped wildlife is restricted or prohibited in many places. Where it is legal it also does not solve the problem — the vacancy is filled within weeks because the space under a deck is what attracted the animal, not that particular squirrel. Check with your state or regional wildlife agency before trapping anything.

How do I know the squirrels have left before I seal it?

Loosely stuff the entrance with crumpled newspaper and leave it two or three days. If it stays undisturbed, nothing is going in or out. Add a dusting of flour at the opening and look for tracks. Do this check even after a one-way door has been in place, because a second entrance you have not found is the usual reason a sealed deck still has a squirrel in it.

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