Bat boxes are artificial roosts designed to encourage bats into areas where there are few roosting sites. There are various designs of bat box from wooden boxes you can make yourself to ready-assembled boxes and even integrated bat boxes that can be built into walls. Different bat species need different spaces.
Wooden bat boxes are usually cubic or wedgeshaped, with a grooved ‘bat ladder’ and a narrow entrance slit at the bottom. They can be nailed to trees or walls.
Below are examples of the Kent bat box. For printable instructions see bottom of page.
Bats do not like draughts, and prefer well insulated boxes where temperature and humidity remain constant. They also need a rough textured wood to cling to. The wood should not be treated because bats are very sensitive to chemicals. A ‘bat ladder’ or other landing area that leads to an entry slit wide enough to admit bats, but narrow enough to keep out predators is also essential, usually 15 – 20 mm. Once up, a bat box cannot be opened legally without a licence. For more information on bats and the law call the Bat Helpline (0845 1300 228).
Things to remember:
• Make sure joints are well sealed and avoid large, loose-fitting front panels.
• All timber used in bat boxes should be rough sawn (unplaned) and untreated from sustainable sources
• Keep entrance slits small (15 -20mm)
• Removable lids should not be used and the box should not be opened
There are two basic types:
• Cylindrical with an access hole in the front and designed to be hung on tree branches with a wire loop; or
• Brick-shaped, usually with narrow roosting crevices inside and an entry slit at the bottom, designed to be fixed to flat surfaces such as walls of buildings, or into the masonry.
Integrated bat boxes are boxes that can be built into the walls and facade of a building. They have the advantage of offering a permanent space for bats with little maintenance and potentially better thermal properties.
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Boxes are more likely to be used if they are located where bats are known to feed. Ideally, several boxes should be put up facing in different directions to provide a range of conditions. Boxes should be put as high as possible in sheltered sunny places. On buildings, boxes should be placed as close to the eaves as possible.Some bats use a tree line or hedgerow for navigation. Putting boxes near these features may help the bats find the box.
• Where bats are known to feed close to hedges and tree lines
• At least 4 or 5m above the ground
• Sheltered from strong winds and exposed to the sun for part of the day (usually south or south-west)
Bats need time to find and explore new homes, and it may be several years before boxes have residents – be patient! Droppings on the landing area, urine stains around the lower parts of the box and chittering noises from inside on warm afternoons and evenings are signs of occupation.