Rodent articles · Updated
Steel wool vs copper mesh for sealing out mice and rats
Both block rodents when packed tight, but plain steel wool rusts, stains and crumbles in humid weather. Copper or stainless steel mesh holds up much longer. Pack it in, then seal over it with exterior sealant.
Both work for a while, but copper or stainless steel mesh is the better choice for a San Antonio house. Plain steel wool rusts when it gets damp, leaves orange stains on brick and stucco, and slowly breaks apart, so the gap opens up again. Copper and stainless mesh don't rust that way and keep their shape.
Either one should be packed tight and then sealed over with an exterior sealant, so it stays put and doesn't pull out.
Why rodents don't chew through it
Mesh made of fine metal strands is unpleasant and hard to chew. A rodent that gnaws at it gets a mouthful of sharp wire and moves on. Foam, caulk and rubber are easy to chew by comparison. That's why mesh goes in first and sealant goes over it, instead of using sealant alone.
The problem with steel wool here
San Antonio summers are hot and often humid, and outdoor penetrations get wet from rain, sprinklers and AC condensate. Steel wool rusts in those conditions. Rust stains run down brick and stucco, and the steel thins out over a season or two. A pad that blocked a mouse in spring can be a loose, crumbly plug by the next winter.
Steel wool can still be fine for a dry interior gap, like under a kitchen sink. For anything outside, use copper or stainless.
Copper and stainless mesh
Copper mesh comes in rolls, usually sold for pest control. It's easy to cut and stuff into irregular gaps, and it won't rust. Over time it darkens, which doesn't affect how it works. Stainless steel mesh is a little stiffer and also holds up outdoors. Both cost more than steel wool, but you're only buying it once.
Want a local technician to take a look? Same-day appointments are often available.
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How to install it
For pipe, wire and line set holes:
- Clean out loose debris and old foam from the gap
- Cut a piece of mesh a little bigger than the hole
- Pack it in tight with a screwdriver or putty knife, leaving no loose ends
- Seal over it with an exterior-grade sealant
- Check it after a few weeks for gnaw marks
Which material goes where on a San Antonio house
Different gaps need different fixes. A quick guide:
- Weep holes: weep hole screens or inserts, never mesh or mortar
- Pipe, wire and line set holes: copper or stainless mesh, then exterior sealant
- Gaps under doors: door sweeps, and a new bottom seal on the garage door
- Gable and soffit vents: galvanized hardware cloth fastened over the opening
- Crawl space vents and skirting: hardware cloth, buried at the bottom of skirting
- Roof-to-wall joints and soffit returns: sheet metal flashing
- Dryer vents: a vent hood with a working flap or a guard made for dryer vents, not mesh that traps lint
Doing it yourself safely
Low gaps are fair game for most homeowners. Wear gloves and eye protection when cutting and packing mesh, since the strands are sharp. Don't block vents that appliances need for air, like water heater and furnace combustion air, or dryer exhaust. In summer, do any attic or roof work early in the morning, because a San Antonio attic gets dangerously hot by midday.
On pier-and-beam houses, crawl space work is cramped and dirty. Our crawl space rodent control page explains what a provider does under the house.
Signs a repair isn't holding
Check your repairs every few months for the first year. Look for gnaw marks around the edges of the sealant, mesh pulled partway out of a hole, fresh droppings near a repair, or rust stains running down the wall from steel wool. Any of those means the patch needs redoing. A repair that still looks tight and clean after a summer and a winter is usually good for a long while. Take a photo of each repair when it's new, so you have something to compare against later.
When mesh isn't enough
Mesh is for small gaps. Bigger openings need sturdier material. Vents, crawl space openings and gaps at the roofline call for galvanized hardware cloth fastened in place. Roof-to-wall joints and soffit returns often need sheet metal flashing. Weep holes need screens or inserts made for them, since packing them with mesh can block drainage. And never stuff mesh into an electrical box or around live wiring.
On a two-story roof or a large job, a provider can do the high work safely. See rodent exclusion for what a full sealing job covers, and how small a hole mice and rats use for where to look.
Ready to have the gaps found and sealed? Call and describe what you're seeing.
Call (210) 955-2948
Questions from callers
Can I use expanding foam alone?
Rodents chew through foam quickly. Use mesh first and foam or sealant over it if you need to fill space.
Is copper mesh safe around pets?
Once packed and sealed, there's nothing loose for a pet to get at. Keep scraps picked up while you work.
Where can I buy copper mesh?
Hardware and home stores usually carry it in the pest control aisle, sold in rolls. One roll covers a lot of pipe holes.
How long does copper mesh last?
Much longer than steel wool outdoors, since it doesn't rust. Check repairs once a year and after storms for gnaw marks or gaps around the sealant.