How to Build and Install a Bat House

Having bats in your yard will help keep mosquitos and other bugs at bay. One bat house can host up to 50 brown bats who eat thousands of bugs each night! Bats are also effective pollinators, especially for tropical plants like guava and agave. Use these bat box plans to encourage them in your landscape.

You might be surprised to know that the minimum size for a functional bat box is larger than most birdhouses. The finished overall size of this piece is 18 inches wide x 26 inches high x 2-3/4 inches deep, with the accessible inside space measuring 16-1/2 inches wide x 22 inches high x 1-1/2 inches deep.

1. Trim Cedar Boards to Size

Natural cedar is ideal for a bat roost. We used three 1 x 6 fence panels. Fence panels are typically less expensive than finished cedar boards that are typically used for interior woodwork.

Use a pencil and a speed square to mark 26 inches from the end on one board then stack all three boards to be cut on the chop saw at the same time. Measure 22 inches on the remaining length and then use the chop saw to cut all three boards down to size. These boards will compose the front and back of the bat roost.

2. Attach Boards Using Simple Joinery

Use a wood joiner to attach the two sets of three boards together. The biscuits and wood glue used here work together to create a very strong connection, though there are many joinery options to consider depending on your resources, including pocket screws.

The three shorter boards will align to create the front of the bat house (22 inches long) and longer boards will form the back panel of the bat house (26 inches long).

On the 22-inch boards, avoid placing joinery around 6 inches from the bottom of the boards. A ventilation channel will be routed at this mark and could damage the joint. Place joinery higher and lower on the boards.

3. Create Grooves on the Inside

A rough texture inside the bat box is necessary, making it easy for bats to grab on and nest comfortably in their dwelling. There are a few different ways to create that texture. One method is to staple plastic mesh on the inside of the panels. The alternative — which we used — is to cut small 1/4-inch horizontal grooves in the wood, making a ladder on which the bats can climb and cling.

A palm router with a 1/4-inch straight bit is perfect for creating horizontal grooves. Use a piece of clamped wood as a straight edge and set the router depth to plunge 1/4-inch deep (the grooves will be 1/4 x 1/4 inch). Continue routing these lines from the top of each panel, towards the bottom.

4. Cut Ventilation Strip

Adjust the router depth to 3/4 inch and use the tool to create a ventilation strip 6 inches from the bottom on the front panel. You may find it easiest to mark the location of the ventilation strip and then re-route the opening once the house is assembled so the straight bit can plunge through easily.

5. Cut and Install Side Walls

Now that you’ve finished the front and back panels of the house, trim the remaining lengths of cedar to size. Use the circular saw to rip the boards in half lengthwise and the miter saw to cut them to size. Use these pieces as the side walls and the roof of the bat house. You will need two 22-inch pieces and one 18-inch length.

Pre-drill the cedar and use galvanized screws to assemble the walls. Lap the corners of the wood and screw through into the front and back panels.

6. Paint or Apply Stain

Dark colors like medium-brown, dark brown or black are recommended for bat houses because they help generate and retain heat from sunlight. Use only latex paint or a natural stain. Bats prefer warmer temperatures, 85 to 100 degrees Fahrenheit. Choose and apply a stain or exterior paint for the bat house.

7. Find the Right Spot and Prep

Location is a big factor to consider when it’s time to install the bat box. The ideal placement is 15 to 10 feet off the ground, mounted on a pole, stand-alone tree or on the side of a building. Position the box to get maximum sun exposure. If you’re installing on a building, be sure there is ground beneath for the droppings to collect (as opposed to allowing them to sit on the roof). If installing on a pole or tree, place a two-foot-wide metal piece below the box, so raccoons, cats and other critters can’t jump over it, but you also have to make sure to place it at least a few feet away from the bat house to allow the bats to drop and fly out of the house.

Use appropriate mounting materials to attach the bat box. To mount it on a tree, attach a T-plate bracket to the back panel and then drill two additional holes for screws in the bottom of the house.

8. Install the Bat House

Use an extension ladder and exercise caution while you install the house. Use a level for accuracy, and a drill to attach the 3-1/2 inch galvanized screws into the tree.