Bats in walls are harder to detect and remove than attic bats, but the exclusion process is similar. When bats roost inside wall cavities, they access the wall from the attic or roofline and climb down between the studs.
Wall-roosting bats are often discovered by scratching sounds inside walls, droppings accumulating at the base of walls, or bats emerging from gaps around windows, doors, or siding. This guide covers how to identify, locate, and exclude bats from wall cavities.
Key Takeaways
- How bats enter walls: Bats climb down from the attic into wall cavities through gaps at the top plate. They usually enter from the roofline.
- Signs of wall bats: Scratching sounds inside walls, guano at wall baseboards, bats emerging from siding gaps, musty odor.
- Exclusion challenge: Wall cavities are harder to seal than attics. Bats may have multiple entry points along the wall.
- One-way valves for walls: Install exclusion valves at the top of the wall cavity (in the attic) where bats exit to the roofline.
- Professional help: Wall bat exclusion is more complex than attic exclusion. Professional help is often recommended.
How Bats Get Inside Walls
Bats do not chew through walls like rodents. They exploit existing gaps in the building envelope. The most common wall entry points are:
- Gaps at the top plate where the wall meets the attic floor , this is the #1 entry point for wall-roosting bats
- Loose siding or trim that creates a gap between the wall and the exterior
- Gaps around windows, doors, or utility penetrations in exterior walls
- Chimney chases (the framed enclosure around a chimney) that have gaps into wall cavities
- Gaps where eaves, soffits, or fascia boards meet exterior walls
Once inside the wall cavity, bats climb down using their claws on the rough interior surface of the wall sheathing. They can travel several stories down within a wall cavity. Big brown bats (Eptesicus fuscus) are the species most commonly found in wall cavities because of their climbing ability.
Signs of Bats in Walls
Detecting bats in walls requires careful observation. Here are the most common signs:
- Scratching and rustling sounds , Most noticeable at dusk and dawn when bats are active. The sound of bats moving inside walls is often mistaken for mice, but it is louder and more deliberate.
- Guano at wall baseboards , Bat droppings accumulate at the bottom of wall cavities. If you see guano along baseboards, it is falling from within the wall.
- Bats emerging from siding gaps , Watch the exterior walls at dusk. If bats emerge from under siding, trim, or around windows, they are roosting in the wall.
- Musty odor , Bat guano and urine inside wall cavities produce a distinctive musty or ammonia smell that may be noticeable near the wall.
- Staining on walls , Urine staining may appear on interior walls, particularly near the top of the wall or around windows.
Pro Tip
To confirm bats in a wall, tape a clear plastic sheet over the suspected entry point on the exterior wall. If bats push through the plastic, you will see the disturbance. Alternatively, use an endoscopic camera inserted through a small hole in the wall cavity to look for bats.
How to Exclude Bats From Walls
Excluding bats from wall cavities follows the same principles as attic exclusion, but with some important differences:
- Locate all entry points , Use the dusk survey method to watch where bats exit. Mark every exit point. Check the top plate in the attic where the wall meets the roofline.
- Install one-way exclusion valves , Install valves at the top of the wall cavity (accessible from the attic) where bats exit. This is the most effective location because bats naturally climb up to exit.
- Seal all other gaps , Seal every gap along the wall except the valve locations. Use copper mesh, caulk, and expanding foam. Pay special attention to the top plate, siding gaps, and window trim.
- Wait 5-7 days , Allow bats to exit through the valves. Verify the wall is empty by listening for scratching and watching for exiting bats at dusk.
- Remove valves and seal permanently , Once the wall is confirmed empty, remove the valves and seal those openings permanently.
Critical Warning
Never attempt to flush bats out of walls by using smoke, noise, or chemicals. These methods are ineffective, inhumane, and illegal in many states. Bats trapped in walls will die, causing odor problems and attracting pests. Always use one-way exclusion.
Challenges With Wall Bat Exclusion
Wall bat exclusion presents several challenges compared to attic work:
- Visibility , You cannot see inside wall cavities. You must rely on sound, exit observations, and droppings to locate colonies.
- Multiple entry points , Bats in walls often use multiple entry points along the same wall. Missing even one can allow re-entry.
- Difficult access , Wall cavities may be difficult to access from the attic. You may need to remove siding or trim to access entry points.
- Guano accumulation , Guano inside walls can attract dermestid beetles and other secondary pests. After exclusion, consider having the wall cavity cleaned by a professional.
- Structural complexity , Walls with fire blocks, diagonal bracing, or multiple stories are more complex to exclude.
Because of these challenges, wall bat exclusion is one of the few bat removal tasks where professional help is strongly recommended. See our DIY vs Professional Wildlife Removal guide for help deciding.
Frequently Asked Questions
How long can bats live in walls?
Bats can live in wall cavities indefinitely if they have access to the outside. They exit at dusk to feed and return to the wall cavity to roost. Wall colonies can persist for years.
Will bats in walls cause structural damage?
Bat urine can damage drywall and wood over time, particularly in large colonies. Guano accumulation can also attract pests. Long-term wall roosts should be addressed.
Can bats in walls enter my living space?
Yes. Bats in walls can enter living spaces through gaps around electrical outlets, light switches, baseboards, or window trim. This is how most unexpected bat-in-bedroom situations occur.
How much does wall bat exclusion cost?
Wall bat exclusion typically costs $500 to $2,000 depending on wall complexity and colony size. See our bat removal cost guide.
Related Resources
🔗 Bat in the Attic Guide · 🔗 Bat-Proofing Your Home · 🔗 How to Inspect for Bats · 🔗 DIY vs Professional Wildlife Removal
Why Trust Us
WildAnimalsCentral.com provides expert-verified guidance on bat exclusion based on NWCOA best practices, state wildlife agency regulations, and consultations with licensed wildlife exclusion professionals. Our wall exclusion methods are reviewed for safety and effectiveness.
