Bats need a rough surface to claw into and use to climb up into the shelter. It is recommended that you score grooves onto the inside surfaces (and landing section) every 1/4 inch. Polyethylene plastic mesh (1/8 inch) can also be stapled to the inside surfaces to achieve a similar (possibly better) design element. Bats also need at least 15 feet of elevation to sail down and get enough speed to start flying. Warmth is also a must so the house needs to be placed in a south or southeasterly facing direction and get at least 6 hours of sunlight a day. If you live in a very warm climate you will need to consider strategic ventilation holes or slots to keep the box from getting too hot. If you live in a cool climate, consider painting the exterior (do not paint the interior) with a non-toxic black paint to absorb heat from the sun.

The sides of the chamber should be about 2 inches deep with a one inch strip of wood attached to the inside of the front panel making the entrance about 3/4 to one inch wide to prevent any predators from gaining access. Your box can have multiple chambers if you like but it is fine to build the first box with only one chamber. Calk the seems to keep out drafts and any moisture. Use exterior grade screws to prevent rust and deterioration. Plan to incorporate an exposed landing strip (with mesh or grooves) at the back base of the of the box extending about 2 inches or so.

Having stated the basics above, the material should be made of exterior grade plywood or cedar. The exterior dimensions should be roughly 24 inches tall, 12 inches wide and 3 inches deep. A ventilated ceiling can also be added to create an important inner temperature variation.

Mounting sites can be on the side of a barn, garage, house, on a pole or in a tree. Bear in mind that bats need to see the house to find it. Try to eliminate obstacles from the flight paths and entrance to the box. Below are pictures to use as a rough guide and for construction ideas. The pictures are of my first bat box project and did not include all the parameters listed above.

Below is a drawing of what the box will look like. I am in the process of building another one for a better picture. I will also design the plans along with a step-by-step procedure and a bill of materials.