How to build a BCM Three Chamber Bat House

Building a Three Chamber Wooden Bat House
Using Bat Conservation and Management's Kit

Three Chamber Bat House
Box parts.
These pre-cut pieces comprise a Three Chamber BCM Bat House (buy an assembled box or kit here now):

1- TOP FRONT: Roughened on the inside face and a beveled top edge to accommodate the sloping roof.

1- BOTTOM FRONT: Roughened on the inside face.

1- BACK: Roughend on the inside face.

1- ROOF: Roughened on the inside face and one edge is beveled to form a sloped roof.

2- SIDES: These parts have the top edge sloped to form the roof. Near the bottom rear edge of each side is a cut out vent. The inside face of each side is grooved to accommodate baffles.

2- ROOF STRIPS: These strips have a beveled edge to accommodate the sloping roof.

3- BAFFLES: This plywood should already be densely roughened on each side.

1- ROOFING MATERIAL
1- SCREEN to be installed over the landing plate on the BACK.
1- tube of roofing cement (not included in Four Chamber Kit) and 35 exterior grade screws

Bat roosting requirements are strict, necessitating adherence to construction details.

You may also be interested
in these instructions:

BCM Bat House Manual

Download a replacement bat house manual that came with your BCM kit.

Pole Mount
(for wooden bat houses)

1: INSPECT FRONT(s), BACK, and each BAFFLE
Lay out all materials and inspect the roughened sides of each BAFFLE, FRONT, and BACK. These surfaces have already been roughened to give bats footholds inside the box. These scratch marks should be no more than 0.25'' apart. Young bats need as many footholds as possible, so use a utility knife to add more scratches on any area which seems neglected. More footholds in the box will make it easier for bats to use the site, which in turn increases the likelihood they will use the box for years to come. NEVER USE A SAW to roughen baffles, as this will cause the plywood to delaminate.
2: ATTACH FRONT to SIDES
Stand the two SIDES up on a workbench along the edge containing the vents. Apply a bead of caulk to the front edge of one SIDE and attach the box TOP FRONT with four screws. The sloping edge of the SIDE should match the sloping edge at the top lip of the TOP FRONT. With one SIDE securely attached, caulk the remaining SIDE and attach with four additional screws. The TOP front is now attached to the SIDES.

Place the BOTTOM FRONT in it's place on the SIDES but leave a 0.5 inch gap between the TOP FRONT and BOTTOM FRONT. Secure the BOTTOM FRONT with six screws, three in each side.

Excess caulk should have squeezed from the joint between the FRONTs and the SIDES, assuring a good seal. Wipe off excess caulk from edges.

3: ATTACH BACK
Caulk back edge of SIDES, but do not caulk the vents. Lay the BACK on to the sides, roughened side in. The top edge of the BACK should extend 2'' beyond the top of the SIDES. This will form an important lip which will be used to mount the finished box to a pole or structure. Securely attach ONE SIDE to the BACK using six screws. Due to minor warping of the wood, the unattached SIDE may not be aligned with the BACK. Manually align the remaining SIDE to the BACK as best as possible without breaking off the SIDE and install the remaining screws.

Extra sealant oozing from the joints is exactly what should happen to ensure a good seal. Wipe off excess caulk from edges.

4: INSTALL rear ROOF STRIP
Center the ROOF STRIP on the inside of the BACK. Align the angled edge of the ROOF STRIP with the angled top edge of the SIDES. Place a straightedge across the top of the SIDES along the BACK. Secure the ROOF STRIP using three screws. Important: angle the screws enough so that screw tips do not protrude out the BACK. Be careful not to overtighten screws or the roof strip may split.

5. INSTALL front ROOF STRIP to FRONT
Center and align a ROOF STRIP along the inside top edge of the TOP FRONT . Make sure the beveled edge of the ROOF STRIP matches the beveled edges of the SIDES and FRONT. Attach with three screws from the front of the FRONT. Angle the screws so tips do not protrude into the bat house interior.

6. ATTACH ROOF
Apply a bead of caulk to top of SIDES, FRONT, two ROOF STRIPS, and angled back edge of ROOF. Lay ROOF in position and attach with three screws into each the back and the front. By angling the back screws, the BACK can be "pulled into" the ROOF forming a tight seal. If too much angle is applied screws will poke out the BACK. Cut off screws using a rotary tool or wire cutters and dab caulk on the screw ends to prevent corrosion. Two additional screws should be placed through the ROOF and into each SIDE. Wipe off excess caulk from edges.

7: INSPECT SEAMS
Caulk back of roof top where it butts against the BACK and smooth with a damp towel. Inspect all seams and add caulk if necessary. Top of box MUST be airtight to hold morning heat.

8: ROUGHEN EXTERIOR
Use the utility knife to roughen around each of the vents as some bats will use the vents as entrances. Also roughen the interior bottom of each SIDE, as bats will use the sides to enter the box. Lastly, the landing plate itself needs to be severely roughened in case the screening (to be installed during step 11) should ever fall off. If the screening is ever lost, DO NOT replace with aluminum screen. Bat excrement reacts to aluminum and the result is poisonous to bats.

9: INSTALL BAFFLES
Slide baffles into grooves in the SIDES. Baffles should not be flush with the roof, but rather stop 1'' from the roof. This void will allow bats to change roosting chambers. Secure the each baffle with one screw in each SIDE. Bats would rather be left in the dark. To help cut down excess stray light from entering the box, use the black spray paint to darken the bottom of the baffles. DO NOT paint the entire baffle, only the bottom few inches is necessary.

10: APPLY STAIN or PAINT
Apply two or three coats of stain or paint to exterior of entire box including the landing plate.

11: FINISH ROOF
Apply thin bead of caulk around roof edges, and form an "X" pattern on ROOF to serve as glue. Lay the roofing material on ROOF, black side up. Staple in place, then caulk all exposed staples. Apply a final bead of caulk along top of roofing material where the roofing material meets the BACK. Check all edges and seams and add additional caulk if necessary.

12: FINISH LANDING PLATE
Place fiberglass screening over landing plate and staple securely. Normally about 20 staples are used all over the screen. Trim excess with utility knife once screen is securely fastened. Coat the staples with black paint.

The box is now complete, but must be placed properly to attract bats.

Note: more detailed plans and instructions are included in actual kits.

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