Bat houses: how to choose, place and maintain one

Why bat houses

Bats are major predators of night-flying insects across the United States, and many species have lost roosts to tree loss, building changes and disease. Bat houses offer a roost for summer colonies. Occupancy is never guaranteed, but a well-built house in the right spot has a better chance. Bat Conservation International, or BCI, publishes the most widely used guidance, and the numbers below follow it.

What to look for in a house

• Multiple chambers. BCI recommends houses with at least two chambers, and more is better, because bats move between warmer and cooler spots as the day changes.
• Roost spacing of about 3/4 to 1 inch. Narrow gaps give bats a good grip and keep heat in.
• Rough surfaces. Bats need to hang on. Screen or grooves on interior walls help.
• Proper ventilation and a landing area. Look for a landing platform at the bottom, with a place for bats to cling and crawl into the chambers.
• Durable, untreated materials. Exterior wood is typically sealed with water-based stain or paint on the outside, while the interior stays unpainted.
• Size. Larger houses are more stable in temperature and hold more bats.

Use our bat house checker to test a location, and read the placement guide for full detail.

Sun, color and temperature

Bats choose roosts for warmth. BCI recommends at least 6 hours of direct sun in places where July average highs are below 100°F, and 10 or more hours in cooler regions where July highs are 80°F or lower. Color then needs to match your climate. Common guidance, based on July average highs, is:

In very hot places such as parts of Texas and Oklahoma, heat is the problem rather than cold, and a house that heats past a bat's tolerance can be abandoned or can kill pups. Read BCI's regional guidance if your summer highs routinely exceed 100°F.

Height, mounting and clearance

• Height. At least 12 feet above ground, and 15 to 20 feet or more is better.
• Mount on a pole or building. Trees tend to put houses in shade, let predators climb to them and sway in the wind. Metal siding can get dangerously hot.
• Clearance. Keep 20 to 25 feet of open space below and in front of the entrance, free of branches and wires, so bats can drop and fly.
• Water. Bats forage near water, and a stream, pond or lake within about a quarter mile helps.
• Timing. Install before the bats return in spring. Occupancy can take time, and there is no fixed time frame that is reliable.

Safety and health

Never handle a bat with bare hands. Bats can carry rabies, as can other wild mammals. If a bat bites or scratches someone, or you find one in a room where people or pets slept, contact your local health department or a physician right away rather than waiting. Do not touch fallen bats. Do not try to relocate or evict bats from a building in summer; many states restrict exclusion during the pup season, when young bats cannot fly. A licensed wildlife professional can advise.

Bat droppings (guano) can carry fungal spores, so wear gloves and a well-fitted dust mask when cleaning up under a house, and do not stir up dust in enclosed spaces.

Expectations

Some houses fill within a year, while others stay empty for several years or never get used. Good placement matters most. If a house is empty after two seasons, look at sun, color, height, nearby roosts and whether the house itself is sound before moving it. Our troubleshooting guide explains how.

Bats you might host

Across the Plains and Midwest, big brown bats and little brown bats are among the species most likely to use houses, with others, such as evening bats and, in the southern Plains, Mexican free-tailed bats, in some places. Eastern red bats and hoary bats roost in trees and rarely use houses. Our bats of the Midwest and Plains guide covers who lives where.

Common mistakes

1. Mounting on a tree.
2. Too little sun or the wrong color.
3. Hanging a single-chamber house too low.
4. Putting it too close to branches or wires.
5. Choosing a house with wide interior gaps or no rough surfaces.