Rodents come in from fields and outbuildings where they find food and shelter. Alabama Extension's approach is exclusion first: block or seal every area where they can enter, then remove food and cover. A rat can use an opening about half an inch wide, and a mouse one about a quarter inch wide.
Key takeaways
- Rats get through gaps about half an inch wide, and mice get through gaps about a quarter inch wide.
- Hardware cloth with half-inch mesh excludes rats, and hardware cloth with quarter-inch mesh excludes mice.
- Steel wool, copper gauze and packed screen wire are temporary plugs, and patching plaster or a similar material is the permanent repair.
- Sheet-metal cones or guards on pipes and cables help stop rodents climbing into a building.
- Refuse and litter should be picked up and stored in a rodent-proof container.
- Poisons alone will not give long-term relief, because the openings and the cover have to be dealt with as well.
Why do rodents move from fields and barns into houses?
Rodents come in from fields and outbuildings where they have cover, food and water. The move indoors tends to pick up as nights cool, and any opening that a rodent can use becomes a route.
Rodents do not need a farm to be a problem, but farmsteads give them what they want. A barn, a machinery shed, a chicken house or a feed store is a building where grain, litter and waste can collect, and where walls and doors have gaps. The areas around the building can give enough cover for rodents to stay close by. For anyone with an outbuilding, the useful question is how many routes lead from it to the house, and how many of those routes can be closed.
The move indoors tends to happen as the weather changes and the nights cool. Rodents that have been living in fields and outbuildings look for warmth and food, and a house with a gap at the foundation or a worn door sweep can offer both. The timing is not something a homeowner controls, but the routes can be closed. Alabama Extension's guidance treats this as the central task: block or seal every area where rodents may enter, and do it before the cooler months draw them in.
How big a gap does a rodent need?
Rats can get through a gap about half an inch wide, roughly a pencil's diameter, and mice can get through one about a quarter inch wide. If a gap is wide enough for a pencil, a rat may be able to use it.
Extension guidance gives the gap sizes that matter. Rats get through openings about half an inch wide, and mice get through openings about a quarter inch wide. Those are small numbers, and they are easy to miss from the outside of a building. The gap around a pipe, the crack where a wall meets the slab, the space under a door and the place where a cable enters a wall are all candidates. Any of them can be big enough once it is measured against a pencil.
The check is simple. Walk the building at night with a torch, look for light coming through, and feel for drafts. Look for droppings near the walls, gnaw marks on the edges of doors and boards, and smears where rodents have rubbed along a wall. Mark each opening you find. A written list of gaps is more useful than a general sense that the building is probably fine, because each gap on the list can be dealt with one at a time.
Which mesh and material should be used?
Hardware cloth with half-inch mesh keeps out rats, and quarter-inch mesh keeps out mice. Steel wool, copper gauze and packed screen wire are temporary plugs, and patching plaster or a similar material is the permanent repair.
Mesh size matters more than the look of the material. Half-inch by half-inch hardware cloth excludes rats. Quarter-inch by quarter-inch hardware cloth excludes mice. A rodent cannot squeeze through an opening smaller than its body, so the mesh should be sized for the smallest animal you need to keep out. Where a gap is covered with mesh, fix the mesh firmly and check it from time to time, since a loose edge invites gnawing.
Temporary plugs have a place. Steel wool, copper gauze or packed screen wire can close a gap quickly while the permanent work is planned. They are temporary, and a proper repair should follow. Patching plaster or a similar material is the lasting repair for a wall or masonry gap. A homeowner who uses plugs should replace them with a proper fix rather than leaving them in place for a season, and should keep a note of which openings were plugged and which were repaired.
How do you guard pipes, cables and drains?
Sheet-metal cones or guards on pipes and cables stop rodents climbing into a building. Floor drain grates should have openings no larger than a quarter inch.
Rodents climb. Pipes and cables that run up from the ground or along a post into a barn or a house give them a ladder, so sheet-metal cones or guards on those lines help stop the climb. Extension guidance treats the guard as part of the exclusion, not an extra. A pipe that is sealed around its base but left unguarded above can still be a route. Look at every line that enters the building from outside, and treat each one on its own terms.
Floor drains need the same attention. A grate with openings larger than a quarter inch can let mice through, so the grate should be chosen to keep the openings small. Check the drains in workshops, feed rooms and any space where water is washed down. A drain that looks sealed from above may still have a gap around its edge. The point is to close the entry, not only the hole that is visible from the floor.
How do you stop rats digging under a foundation?
Rats dig, and a buried curtain of half-inch hardware cloth extending 12 inches down gives them a barrier below the surface. Digging is often the route for a rat that cannot find an opening above ground.
Rats can dig under a slab, a skirting or the edge of a building. Extension guidance describes a buried curtain of half-inch hardware cloth that extends 12 inches down, which gives the rat a barrier below the surface. The curtain goes where the digging would otherwise happen, usually along the edge of a foundation or a slab that sits on the ground.
A curtain closes that route without changing the look of the building. It is easier to put in during a repair than after a rat has been using a burrow for a season. A technician will look at the edges of the building, the slab and any gaps at the ground, and say which of them need a curtain and which need a plug. The rodent control and exclusion service covers the exclusion work in more detail.
What about refuse, feed and clutter?
Food and cover keep rodents in place. Pick up litter and refuse, and store it in a rodent-proof container, so the building is less attractive to the animals that have found it.
Exclusion alone does not finish the job. Extension guidance pairs it with sanitation, which means removing what rodents eat and the places where they nest. Pick up all refuse and litter around the barn, shed or house. Store refuse in a container that rodents cannot get into. Keep feed in sealed containers, off the floor. Move piles of stored material away from the walls, so there are no hiding places close to a gap.
Traps can be part of the work. Extension guidance notes that peanut butter sticks to a trap trigger, which is a useful detail when the bait has to stay put. Poison alone will not give long-term relief, though. A rodent that still has food and cover will come back, and a poison that kills one animal does nothing about the route the next one takes in. Any poison use should be part of a plan that closes the openings and removes the cover at the same time.
When should you call a technician?
Call when droppings keep appearing, when rodents are getting inside the house, or when the outbuildings are large enough that the gaps are hard to find. A visit should end with a list of openings.
A technician is most useful when the building is large or the routes are hard to read. A barn, a machinery shed or a chicken house can have many gaps, and some of them will be behind equipment, stored material or at the edge of a slab. The visit should produce a list of openings, a plan for each one, and a clear statement of what the homeowner can close alone and what needs more work. Ask for that list at the end of the visit.
Call (855) 974-4733 to ask for a visit. Phones are answered 24/7, and a visit the same day is possible only when a technician is free, so no arrival time is promised. When you call, describe the buildings and how each one is used, whether there is stored feed or refuse, and where you have seen droppings or gnaw marks. That information lets the technician plan the visit around the gaps rather than guessing at them.
Frequently asked questions
Which mesh should I use on a barn?
Half-inch hardware cloth excludes rats, and quarter-inch hardware cloth excludes mice. Quarter-inch mesh keeps out both, so it is the one to use where the smaller animal is a concern. Fix the mesh firmly and check it, since a loose edge invites gnawing.
Do steel wool plugs work?
They work as a temporary plug. Steel wool, copper gauze or packed screen wire can close a gap for a while, but a permanent repair such as patching plaster or a similar material is the lasting fix. Keep a note of which openings were plugged so they can be repaired later.
Is poison enough to get rid of rodents?
No. Extension guidance says poisons alone will not give long-term relief. Exclusion, sanitation and chemical control are used together, with the openings closed and the refuse removed, so that the building stops being a place rodents want to stay.
How do I stop rats digging under a barn?
A buried curtain of half-inch hardware cloth extending 12 inches down addresses rats digging under a slab or foundation. A technician can say where a curtain would go on your building, since the edges and the ground contact vary from one structure to the next.
Do rodents climb pipes?
Yes. Pipes and cables give rodents a ladder, so sheet-metal cones or guards on them help stop the climb. Treat every line that enters a building from outside, not only the ones that are easy to see.
Does this site publish a price for rodent work?
No. This site does not publish prices. The technician confirms the price on site before any work starts, and the cost guide on this site explains what moves a quote for this kind of work.
Sources
This guide is general information for Bibb County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.