Using recycled wood – such as mushroom wood – not only provides a beautiful finish but also increases the odds of luring bats to live in a bat house. While one may not think attracting bats to the backyard is a good idea, bats are an excellent way to reduce mosquito populations. And as they are primarily nocturnal, bats do the work while you sleep.

Mushroom wood refers to hemlock or cypress boards used as shelves for growing mushrooms at farms in Western New York State and Pennsylvania. The mushrooms grow in a sterilized substrate laid directly on the shelves. As the mushrooms grow, they produce an enzyme that eats away at the soft tissue of the wood; leaving behind most the durable and rot-resistant part of the wood. Periodically the shelves are replaced and the old wood – with its unique and beautiful patina – is reused for furniture, paneling, and other indoor or outdoor projects.

Attracting bats is a mixture of know-how and luck. Bats like to live in a relatively small enclosed space that will help capture their body heat and prefer to enter through a small opening in the base of the structure. Bat houses are best placed away from the home – on a garage or barn – at least 15 feet above ground. Hanging more than one bat house will increase the odds of attracting bats to roost.

Since heat is an important factor in bats’ choosing to move into a bat house, location is important. In areas where the average summer temperature is below 85F, a bat house should face south and southwest to take advantage of the warm sunlight. Where the average summer temperature is above 85F, a bat house should be positioned in a more northerly direction and out of direct sunlight.

This project can be easily made with other lumber (preferably recycled) if mushroom wood is not at hand. Again, studies have shown that recycled lumber is more likely to attract bat tenants.

Materials:

Antique cypress mushroom wood:
One 1”x8”x6’ board, brushed (more rustic look)
One 1”x8”x8’ board, planed
Stainless steel shank nails 1 ¼” & 1 ½”
Fiberglass screen
3/8” staples
Translucent exterior caulking

Tools:

Table Saw
Miter saw
Tape measure
Hammer
Staple Gun
Pencil

Directions:

1. Cut planed 1”x8”x8’ board into four 15 ½” lengths and two 22” lengths.

2. Create back wall of bat house, 15 ½” wide x 24 ¾” tall. Use table saw to rip down 15 ½” lengths into three 6” widths. Set blade of table saw to 15 degree bevel to rip fourth board into 6 ¾” width, to accept pitch of roof.

3. Return table saw blade to 90 degrees and set blade to 1/8” depth. Make a series of grooves lengthwise on bottom 3” of one 15 ½”x6” board to be a landing pad for bats to cling to. Space grooves ¼” apart. This board will be the bottommost board on the back wall, with grooves at bottom end.

4. Use table saw to rip down 22” piece into three 1 ½” widths and one 1” width. Set aside 1” board.

5. Using miter saw, create side walls of bat house by cutting a 15 degree angle on one end of two of the 1½”x 22” pieces with miter saw. Cut other ends at right angle to create two 21 ½” lengths.

6. Place side walls on work surface parallel and about 15 ½ inches apart. Position the back side of the four boards of back wall on side walls. Line up beveled edge of top board with angled edge of side walls. Position landing pad grooves at the bottom of the back wall, facing toward the front. Sides of bat house will be shy of bottom edge of back wall, leaving landing pad grooves exposed. While attaching pieces together, apply thin layer of caulk between boards to waterproof seams and fasten the back boards to the side walls with 1 ½” stainless steel nails.

7. Use miter saw to cut one 1 ½”x22” board to a length of 14”, to be ceiling of bat house interior. Turn structure over and attach ceiling to top end of back wall, just below the lowest point of side wall angles. Fasten with nails, using think layer of caulk to waterproof structure.

8. Use 3/8” staples to attach a piece of fiberglass screening to the inside of back wall. Screening will provide a surface for the bats to grab onto once inside the house.

9. Install front panels of house. Use miter saw to cut brushed 1”x8”x6’ into four lengths of 15 ½”. Use table saw to rip three panels into widths that will cover entire face of house and stop flush with bottom edge of side walls, leaving grooved overhang exposed. Bevel top panel 15 degrees along its top edge to line up with roof line. Position boards on house, caulk, and fasten top two boards of the front wall.

10. Use miter saw to cut remaining 1”x22” piece (from step 4) into a 14” length. Set table saw blade to 45 degree and create bevel on 1” side. Fasten this piece to inside bottom center of remaining board for front wall, such that it will fit snugly between the two sidewalls when the third board is attached to the front of the bat house. Also, ensure that the bevel will face up when the third front board is attached.

11. Position third front board on face of bat house, creating a ¾” opening for bats to enter on underside of the bat house above the grooved landing pad. Caulk and fasten with nails.

12. Create roof by ripping down the final remaining brushed-finish board to 5” wide with a 15 degree bevel on the top edge. Caulk and fasten to the top of bat house. Hang in appropriate location.