Mice in Your Basement? How They Get Into Philly Row Homes

Video transcript

On-screen captions: This is the dark, dusty, drab basement the client employed us to clean and brighten. In row houses or twins, mice frequently travel between floor joists from house to house. For our special mice mix we use concrete sand, lime, cement and we integrate glass and fine metal fibers to prevent mice from penetrating through our concrete. Mice can fit through small holes therefore we use a sponge and a paint brush to create an airtight seal between the floor joists and the cement. And now it's time to apply paint to the walls and brighten the basement. First coat white primer, second coat bright white semi-gloss. Now see how this basement is coming together, it's brighter, it's livelier. Our client can now enjoy their bright, clean, dust and rodent free basement. On screen: a Philadelphia row house basement before and during the work — sealing gaps at the joists and floor, coating the walls, finishing the floor — then the finished room with white walls and a smooth gray floor. End card: Dependable Concrete LLC, doing concrete in Philadelphia since 1984. Your written estimate within 24 hours of our visit. dependableconcrete.com, 215-821-9779, Book Your Estimate.

Why Mice Show Up in the Fall

Mice live outside all summer without much trouble. When it gets cold, they want warmth and shelter, and a basement gives them both. A row house basement is also dark and quiet, and it's often full of storage boxes to hide behind.

They don't need much room either. A gap you'd brush off as nothing can be plenty for a mouse. So the question isn't really whether your house has an opening. Most older homes have a few. It's whether you've found them.

1. Under the Garage Door

A lot of Philly row homes have a garage at basement level, opening onto the back driveway. That's a common way in.

Over the years the concrete at the bottom of the door wears down, cracks, or sinks. The door closes but doesn't sit flat on anything solid anymore. You end up with a gap along the bottom, sometimes just at one corner.

What to check: Close the garage door and look from the inside with the lights off on a sunny day. If you can see daylight along the bottom, something smaller than your hand can get through. Also look at the slab right outside the door. Is it broken up, chipped at the edge, or lower than the floor inside?

How we fix it: We cut out the broken concrete and pour a new apron or threshold so the door closes down on a flat, solid surface. When the slab is level and whole, the door's bottom seal has something to press against.

2. Cracks and Holes in the Basement Floor

Old basement floors in this city take a beating. Some were thin to begin with. Some have been patched a few times. Some are broken around an old drain or along the edge where the floor meets the wall.

Mice will use a crack that's opened up, a hole where a chunk of concrete broke out, or a spot where the floor has pulled away from the wall. Bare dirt sections, which you still see in some older basements, are even easier.

What to check:

• Cracks you can fit a pencil tip into
• Spots where the floor has broken into loose pieces
• The joint where the floor meets the wall, all the way around the room
• Any patch of dirt that was never covered

How we fix it: Small cracks get cleaned out and filled. When the floor is broken in a lot of places, patching usually isn't worth it, so we either resurface the old floor or tear it out and pour a new one. A new floor runs tight to the walls all the way around, so there's no gap left along the edge.

3. Where the Floor Joists Meet the Party Walls

This one's specific to row homes, and most people never look at it.

Your first floor sits on wooden joists. In a row house, the ends of those joists rest in pockets cut into the party walls, the shared walls between you and your neighbors. Over a hundred years, the mortar around those pockets dries out and falls away. That leaves gaps at the top of the basement wall, right where the joists go in.

Those gaps can run into the wall cavity and toward the house next door. If your neighbor has mice, this is one of the ways they get to you.

What to check: Take a flashlight up to the top of the basement wall where the joists meet it. Look for open space around each joist end, missing mortar, or crumbling spots. Droppings along the top of the wall are a giveaway.

How we fix it: We clean out the loose material and pack the open spots around the joist pockets with mortar so the gaps are closed off. We also seal other openings we find in the foundation, like holes where old pipes or wires used to run.

4. The Walls Themselves

A lot of Philly basements have stone or brick walls. When the old cement coat cracks and falls off, the joints behind it open up. Over time that leaves holes and soft spots that run back into the wall.

What to check: Look for places where the wall coat has flaked off, where you can poke into the joints with a screwdriver, or where sand and grit keep piling up on the floor along the wall.

How we fix it: We fill the open joints, then parge the wall, which means putting a new cement coat over it. You get a solid wall face again, with nothing open for a mouse to get into.

What Concrete Work Can and Can't Do

Let's be straight about this. Sealing up your basement closes the openings. It doesn't get rid of mice that are already inside, and we don't do pest control. If you already have mice, call an exterminator for that part.

What we do is close the gaps in the floor, walls and slab so it's a lot harder for them to get in. If you're doing both, it usually makes sense to seal up first, or right after the exterminator's done, so you're not just making room for the next batch.

A Quick Fall Checklist

Grab a flashlight and give your basement 15 minutes:

1. Garage door closed, lights off. Any daylight at the bottom?
2. The slab outside the garage door. Broken, sunk, or chipped?
3. The basement floor. Cracks, holes, loose pieces, or dirt patches?
4. The edge where the floor meets the walls, all the way around.
5. The top of the walls where the joists go in. Any open space?
6. Old pipe and wire holes in the foundation walls.
7. Droppings or chewed stuff anywhere along the walls.

If you find a couple of these, it's worth having someone look at them before winter really sets in.

Common Questions

How do mice get into row homes?

Mostly through the gap under a basement garage door, cracks and holes in the basement floor, and gaps around the floor joists where they sit in the party walls between houses. Open joints in old stone or brick walls are another common route.

Can you seal basement floor cracks in winter?

Yes. The work is inside the basement, so cold weather outside doesn't stop us.

Will sealing my basement get rid of mice I already have?

No. Sealing closes up the ways in. Mice already inside are a job for pest control.

Do I need a whole new floor?

Not always. A few cracks can be filled. If the floor is broken up in a lot of spots or has dirt sections, resurfacing it or pouring a new one usually makes more sense. We'll tell you which one your floor needs after we see it.

Get Your Basement Sealed Up

Dependable Concrete LLC is family-owned and has been pouring concrete in Philadelphia since 1984. We mix our own concrete, and we handle the floor, the walls, the joist pockets and the garage apron ourselves.

Your written estimate within 24 hours of our visit.

Dependable Concrete LLC
215-821-9779
dependableconcrete.com

Book OnlineCall 215-821-9779dependableconcrete.com

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