Bats are so threatened by toxic insecticides that they need all the help they can get. A bat box can be made from untreated, preferably rough-sawed timber.
Directions for Making a Bat Box
There is no front entrance hole, but instead a 3/4″ (2 cm.) base entry slit.
Back: 16″ x 6″
Front 5″ x 6″
Side: 8″ x 25 cm
Side: 10″ x 20 cm
Roof: 9″ x 12.5 cm
Base: 3 3/4″ x 4-5 cm
Before fixing the wooden sections together, panel-pin or drill and screw two bat perches against the inside of the back wall. These are made of wood 1/2″ (1.25 cm) square and 4″ (10 cm) long.
The hinge is once again made from a strip of rubber cut from an old wellington boot and tacked on to the roof and back panel, forming a weatherproof joint.
Two hooks and eyes should be used to secure either side of the roof against wind and squirrels. Bats are protected by law, and so although a hinged roof is useful, casual inspections should not be carried out.
Bats prefer to roost high off the ground (think of a church belfry, for instance). So a position about 6 yards high on a wall or tree trunk would be ideal. However, if this is not possible, it is worth experimenting at lower levels. When siting the bat box, avoid facing it due east or west.