Are you in a seemingly never-ending battle with rats or mice getting into your home?
Wondering how to find their entry points, and seal them out for good?
This article will teach you the common rodent entry points and gives you instructions on how to seal them best to keep rats & mice out of the house permanently.
And this will also help you control rodents without killing them.
1. Foundation Vent Screens
Damaged or missing foundation vent screens is the first place to look for when trying to seal off rodent entry points.
This is probably the most common way for rodents to get inside your home, if you have a crawlspace with vents. Sometimes HVAC, cable, electrical, radon, gas, plumbing, or other utlitity contractors breach the foundation vent screens to run their utilities from outside to inside your house.
Then they leave them open for rodents to find…
How to seal foundation vent screens:
• Use 1/4″ hardware cloth, cut to exact size, and firmly placed into the plastic vent screen housing. Then, use lathe or sheet metal screws, and the lowest setting on your electric driver to fasten the replacement screen to the housing.
• To seal around utility pipes going through a foundation vent: Use tin snips to cut lines into the hardware cloth replacement screen at the general position of the utlity pipe, then use a hardening foam to seal any remaining gaps around the utlity at the junction with the screen.
• Sometimes, you may need to fasten the 1/4″ hardware cloth to the foundation wall to seal the vent screen. Use concrete anchors like Tapcon, or a powder actuated tool like Ramset to secure hardware cloth to concrete.
2. Gutter lines
If you’re hearing noises in the attic, that is a clue.
You should start by checking around your eaves & gutters for gaps or gnawed holes.
Oftentimes, there is a gap between the top edge of the gutter, and the bottom edge of the roof.
Use a ladder to climb up to visually inspect for gaps along the the top edge of the gutter.
Wearing gloves, use your hand to feel for gaps if you can’t see because the drip edge hangs over the top edge of the gutter.
How to seal gaps along gutter lines:
• The very best thing to seal rats, mice and squirrels from entering atop your gutters is to have the entire gutter section removed. Then the fascia board (the board the gutter is hung to) should be replaced to close the gap.
Or, you can use long sticks of 90 degree metal flashing to exclude the gap by securing one side to the fascia, and having the other side of the 90 degree bend placed under the roof board. Be careful not to damage the shingles.
• If you cannot remove the gutter, you could try loosening the gutter, and sliding flat pieces of metal flashing behind the gutter (between the fascia board and the back of the gutter) to exclude the gap. Leave enough material on the bottom so that it extends under the bottom of the gutter, so you can handle and secure the flashing.
**DO NOT rely on spray foam to exclude rodents and mice, they will easily gnaw through it!
3. Dormer corners & Roof junctions
If the gutters look good, and you’re still hearing noises in ceilings or second story walls, check any dormers or intersecting roof lines.
Oftentimes, gaps in construction are left at the seams.
Where two roof lines intersect, they create a shadowy space where rodents like to hide. If there is a gap, they have easy access to your attic & wall voids.
For this, you might need to get on the roof.
If your roof is steep and you’re not comfortable with that, you’ll want to reach out to a roofer or a licensed wildlife control operator.
Explain your situation, and ask if they are able to inspect & work on roofs.
How to seal gaps at dormer corners & roof junctions:
• As pictured above, use a piece of metal flashing (comes in rolls from the hardware store).
• Measure the distance from the inner wall, and the outer edge of the roof or barge board. With tin snips, cut the metal flashing to size.
• Fold the metal flashing in a way that fills & excludes the gap.
• Fasten with grommited roofing screws and be sure to cover any exposed penetrations in the roof surface with roofing sealant.
**WEAR gloves when handling metal flashing to prevent cuts & injuries.
Click to Get Rid of Rats. 
4. Burrows
Rats and mice are great burrowers. Sometimes they tunnel underground into your crawlspace.
If any part of your house is on a crawlspace, with an earthen floor, you might have rodent burrow entries.
In some situations, you can dig a trench along the area where the burrow enters, and place a mesh “skirt” around the area to exclude the burrow entry.
Installing mesh skirting to seal out mice & rats is helpful for the following situations:
- Rodents burrowing under concrete block foundations or slabs,
- Rodents entering at gaps along the mud sill, or foundation,
- Rodents entering underneath the bottom sill of your crawlspace entry (pictured above).
- Keeping rodents out from under porches, sheds, and additions
Some rodent burrows are too deep, or to active to be able to effectively exclude with mesh skirting. Rats and mice can excavate their burrows around the skirting. And it’s not recommended to try to skirt a whole foundation. You could risk destabilizing your entire home.
In those cases, leave traps in the crawlspace at all times, and check them regularly.
How to seal rodent burrows:
• Dig a trench that is at least 18″ deep, and 18″ wide along the area of burrowing activity.
• Using 1/4″ hardware cloth (important: not 1/2″), cut to size and bend into an L-shape to create the skirting.
• Place the mesh skirting flush along the foundation wall, and level ground, and fasten to the foundation or house as needed.
• Backfill the trench to bury the skirting. Compact the soil as best as possible.
**Consider leaving traps in your crawlspace at all times, and check them regularly. This way you can monitor rodent activity, and help prevent them from getting out of control.
5. Gaps in Construction
This category is a catch-all for any other gaps or holes where rodents could enter.
Rats and mice don’t usually enter through solid walls.
They almost always find an existing gap, at the intersection of two construction elements, and enter through that way.
Some of these common gaps are described above; gaps along the gutter and roof intersection, gaps along roof junctions, etc.
Other junctions & intersections may be unique to your home’s architecture.
How to seal rodent entry points:
• Check all around the perimeter of your house;
- Under the edge of the siding,
- Where porches & additions meet the main home
- Around utilities & pipes,
- Around doors & windows,
- Foundation vents & crawlspace doors,
- Any intersection of different construction elements
- Around the perimeter for burrows,
- And anywhere else you can visually inspect
Use metal flashing or 1/4″ hardware cloth to seal any gaps greater than 1/4″. If the gaps are small or can’t be sealed with metal, use a stainless steel wool exclusion fabric to fill the gaps.
**Check for evidence of gnawing, sebum (dirt rub marks), or the absence of debris and spider webs. These things could indicate an active rodent entry point.
These steps are part of a complete integrated rodent management plan, and will help you keep mice & rats away from your house effectively.
Sometimes a professional inspection can be worth it. They will use their experience to help you find the rodents entry points, and put together a plan to get them sealed up permanently.
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