How to Get Rid of Bats in Your House (DIY Exclusion Guide)

Bats roost in attics, wall voids, soffits, chimneys, and behind shutters. The two most common house-dwelling species in the US are little brown bats and big brown bats. They enter through gaps as small as 3/8 inch — about the width of a dime — and a single colony can number anywhere from a handful to several hundred.

Why exclusion, not extermination? Three reasons:

• It's the law. Most bat species are protected under state and federal wildlife laws. Killing bats can result in significant fines. Some species (like the Indiana bat and northern long-eared bat) are federally endangered.
• It's the only thing that works. Repellents, ultrasonic devices, and mothballs do not work on bats. Period. Exclusion is the only proven method.
• Bats are ecologically critical. They consume massive quantities of insects, including mosquitoes and agricultural pests. One colony can eat tens of thousands of insects per night.

Critical timing rule: NEVER exclude bats from May through August. This is maternity season — flightless pups are inside the roost. Sealing adults out during this period traps babies inside, where they die and create a much worse problem. Exclusion should happen in early spring (March–April) or late summer/fall (September–October).

• One-way exclusion devices — You can buy commercial bat exclusion tubes (like the Batcone II) or make your own from 2-inch PVC pipe or flexible polypropylene netting. The idea: bats can crawl out but can't find their way back in.
• 1/4-inch hardware cloth or metal mesh — For permanently sealing entry points after bats have left.
• Polyurethane caulk — For sealing small gaps (under 3/8 inch).
• Expanding foam + steel wool — For filling larger gaps in combination with mesh.
• Staple gun or screws — For attaching mesh and netting to your home.
• Ladder (extension ladder for multi-story homes) — Most entry points are at the roofline.
• Flashlight and binoculars — For evening observation of bat exit points.
• Caulk gun — For sealing work.
• Heavy work gloves — Never handle bats with bare hands (rabies risk, even from dead bats).

Step 1: Confirm You Have Bats (Not Birds or Mice)

Signs of a bat roost:

• Guano (bat droppings) — Small, dark, pellet-shaped droppings that crumble when crushed and contain shiny insect fragments. Found below entry points, often in small piles on the ground, windowsills, or attic floor. Mouse droppings are similar in size but don't contain insect parts and don't crumble the same way.
• Staining — Dark, oily rub marks around entry holes from bat fur oils.
• Squeaking or scratching sounds — Especially at dusk and dawn. Bats are most vocal when leaving and returning.
• Visual confirmation — At dusk (about 20 minutes after sunset), watch your roofline. You'll see bats emerging from their entry points. This is also how you identify exactly which gaps they're using.

Step 2: Identify ALL Entry Points

This is the most critical step. Miss one entry point and the entire exclusion fails — bats will just use the gap you missed.

Do an evening watch: On 2–3 warm evenings, position yourself where you can see the roofline and watch for 45 minutes starting 15 minutes before sunset. Note every spot where bats emerge. Have a second person watch a different side of the house if needed.

Do a daytime inspection: With a ladder, inspect every inch of the roofline, soffits, fascia boards, gable vents, ridge vents, chimney flashing, and where different building materials meet. Look for:

• Gaps at the junction of soffits and walls
• Loose or missing fascia boards
• Gaps around chimney flashing
• Open or damaged gable vents and ridge vents
• Gaps where dormers meet the roof
• Construction gaps where additions meet the original structure
• Any gap 3/8 inch or wider — remember, that's all it takes

Mark every potential entry with tape or chalk. You will likely find 5–15+ potential entry points on a typical home.

Step 3: Install One-Way Exclusion Devices at Primary Exits

At the 1–3 main entry points you identified during your evening watch, install one-way exclusion devices:

Option A — Commercial bat cones (Batcone II): These are clear plastic tubes that insert into the gap. Bats crawl through and drop out the bottom but can't fly back up into the tube. Attach with caulk or staples around the flange.

Option B — DIY netting exclusion: Attach a piece of lightweight polypropylene netting (1/4-inch mesh or smaller) above and to the sides of the entry point, leaving the bottom open and hanging at least 2 feet below the gap. Bats crawl down and out under the netting but can't find their way back up and behind the netting to re-enter. Secure the top and sides with staples — the bottom must hang freely.

Option C — PVC pipe excluders: Insert a 10-inch length of 2-inch PVC pipe into the gap at a slight downward angle. Bats crawl through and out but can't navigate back through the tube. Seal around the pipe with caulk so the pipe is the only way out.

Step 4: Seal ALL Secondary Entry Points

While the one-way devices are on the main exits, seal every other potential entry point you identified. Use:

• 1/4-inch hardware cloth — Screwed or stapled over gable vents, ridge vents, and larger gaps.
• Caulk — For gaps under 3/8 inch.
• Steel wool + expanding foam — For gaps between 3/8 inch and 1 inch.
• Metal flashing — For gaps along the roof edge and chimney.

Important: Do NOT seal the main exit points yet. Those still have the one-way devices on them.

Step 5: Wait 5–7 Days

Leave the one-way exclusion devices in place for at least 5–7 warm nights (above 50°F). Bats won't leave on cold or rainy nights. During this period, continue doing evening watches to confirm bats are exiting through the one-way devices and not finding alternative entry points you missed.

After 5–7 nights with no bats observed re-entering, the roost should be empty.

Step 6: Remove Exclusion Devices and Permanently Seal

Remove the one-way devices and permanently seal those final entry points with hardware cloth, caulk, or metal flashing. Your home is now bat-proof.

Step 7: Clean Up (If Needed)

If guano has accumulated in the attic, clean it up wearing a respirator (N95 minimum), goggles, and gloves. Bat guano can harbor Histoplasma capsulatum, a fungus that causes histoplasmosis, a respiratory infection. Mist the guano with water first to reduce dust. Bag it in heavy-duty trash bags. For large accumulations (more than a few square feet), consider professional cleanup.

• Annual roofline inspection — Check soffits, fascia, ridge vents, and chimney flashing every spring for new gaps. Homes settle and materials deteriorate over time, creating new entry points.
• Screen all vents — Gable vents, ridge vents, and attic vents should have 1/4-inch hardware cloth screening. Standard window screen is too flimsy — bats can push through it.
• Maintain chimney caps — A properly fitted chimney cap with mesh screening prevents bats (and birds and raccoons) from entering through the chimney.
• Install a bat house — If you want the insect control benefits of bats without them living in your attic, install a bat house on a pole or the south-facing side of your house, at least 12 feet up. Bats may relocate to the bat house after exclusion.
• Seal construction gaps on new builds and additions — The junction where an addition meets the original structure is a common bat entry point. Address this during construction, not after.

• Excluding during maternity season (May–August) — This is the most serious mistake. Flightless bat pups will be trapped inside and die. Besides being inhumane, dead bats in your walls create a terrible odor and attract other pests. In many states, excluding during maternity season is also illegal.
• Missing entry points — If you seal 14 out of 15 gaps, bats will find the 15th. Multiple evening watches from different angles are essential to identify every exit point.
• Using repellents instead of exclusion — Mothballs, ultrasonic devices, bright lights, peppermint oil — none of these work. Bats have been studied extensively, and no repellent has been shown to reliably deter them. Exclusion is the only method.
• Sealing entry points without one-way devices — If you just seal bats in, they'll die inside your walls (odor, flies, disease risk) or desperately find their way into your living space through gaps in interior walls. Always let them leave first.
• Handling bats without gloves — Even a seemingly healthy bat can carry rabies. Never touch a bat with bare hands, alive or dead. If you find a bat in your living space, contain it under a container and slide cardboard underneath, then release it outside (or contact animal control if someone may have been bitten).