build a bat conservation International's bat box

A bat house designed by Bat Conservation International combines relative ease of construction with the varied crevice sizes most often used by American bats and temperature buffering features.  Western red cedar is recommended for its ability to withstand outdoor exposure, though many other woods are suitable.  Six feet of 1 X 12-inch board are sufficient for construction (Actual board sizes normally are about 3/4 X 11 1/4 inches.)  Overall dimensions may be varied to allow for slight differences in board widths or personal preferences, but spacing between partitions should remain approximately the same.  Use rough lumber and turn the rough sides inward.  The rough side of the roof, front, back, and sides inward.  The rough side of the ceiling should face down.  Cut 1/16-inch horizontal grooves at 1/2-inch intervals ont he smooth sides of all partitions.  This will enable bats to climb and roost.  Apply a bead of silicone caulk along each exterior joint to prevent heat loss.  The estimated cost of materials is less than $20, and a single house may be occupied by a hundred or more bats.  A small bat house design used in Europe.  These are usually 10 or 12 inches wide; the exact dimensions are unimportant.  As many as 30 bats have been found occupying this type of house.

DIMENSIONS

A           ROOF 16 1/2" X 11 1/4"
B            FRONT 18 3/4 X 9 1/
C           BACK 27" X 9 1/4"
D           CEILING 9 3/4" X 9 1/4"
E            PARTITIONS              9 1/4" WIDE X 8" HIGH
F            PARTITIONS              9 1/4" WIDE X 14" HIGH
G           SIDES 11 1/4" WIDE X 27" AT BACK, 18 3/4" AT FRONT

SPACING BETWEEN PARTITIONS FRONT TO BACK 3/4", 3/4", 3/4", 1", 1 1/2", 1 1/4" 

from Tuttle, Merlin D.  1988.  America’s neighborhood bats.  Univ. Texas Press.  Austin.    96 pp.