Bats are super cool. They eat loads of insects every night and some studies even suggest that the mere presence of bats is enough to keep annoying mosquitoes away. Plus, they’re fun to watch! Bat boxes are a great way to attract bats and keep them coming back to your yard, but some commercial options cost hundreds of dollars. We’re walking through the steps to build your own DIY bat box for $20 or less!
Happy Halloween! While bats are synonymous with the spookiest of holidays, they’re not spooky at all! They’re incredibly mosquito-gobbling machines that you actually want on your property! We see bats pretty frequently at our Michigan Tree House, but we love the idea of attracting them and encouraging them to stick around. When we saw a pitch for beautifully designed bat boxes on a recent episode of Shark Tank, we were inspired to try our hand at building a DIY version!
Bat Box Mounting Location Requirements
Before we get started on the tutorial, a functional bat box that will attract (and hopefully retain) bats requires a few key mounting location features:
- The location should receive direct morning sunlight. East or Southeast facing is best. Bats prefer temps from 85 – 100 degrees Fahrenheit so the sunlight helps them stay warm and comfortable!
- Mounting position should be 10+ feet from the ground with no obstructions below the box to allow for free flight into and out of the box.
- There should be a water source (lake, pond, river, stream) within 1/2 mile of the box.
Bat Box Construction Requirements
Ideally, there should be…
- … a narrow opening of around 3/4″ across the bottom to provide security and deter predators.
- … a ‘landing pad’ with a grooved or textured surface.
- … dark stain or paint for better heat retention, however, a lighter finish is OK in warmer climates.
- … caulked/sealed joints to keep out drafts and elements.
- … a sloping roof to allow for drainage.
- … ventilation to allow for internal temperature regulation.
Note: Bat boxes can be built in many shapes and sizes. Some even have multiple chambers inside that can accommodate hundreds – yes, hundreds! – of bats. We started small with a single chamber box that uses minimal supplies. With the exception of the exterior-rated plywood, we had everything else on hand!
Tools + Supplies Used for 18″w x 24″h Box
- Drill + Coated 1 1/4″ deck screws (Option 1, our anticipated construction method): preferred if painting box
- Nail gun + 1 1/4″ nails (Option 2, our final construction method): preferred if staining box
- 2 x exterior grade plywood sheets – 1/2″ x 2′ x 2′
- 1 x cedar or pressure treated 2″ x 4″ x 6′ board
- 1 x cedar fence picket (or use leftover plywood)
- Tape Measure
- Table Saw (optional)
- Miter Saw (can also use hand saw)
- Aluminum mounting cleat
- Speed square
- Sanding block
- Stain of your choice (+ Polycrylic) or exterior grade paint; darker finishes should be used in cooler climates
- Aluminum French cleat (for mounting)
Prepping the Front + Back Panels
We started by cutting each of the 2′ x 2′ panels down to an 18″ width. Once we were happy with the size of the front and back panels, we were ready to provide traction for our flying friends! For aesthetics and durability, we chose to cut shallow grooves on the interior surfaces of the plywood. Think of it as a tiny lil’ bat ladder!
We set our table saw blade so it protruded 1/8″ above the table surface. We then passed the plywood over the saw every 1/2″ until both interior plywood surfaces were completely grooved horizontally from top to bottom. Making 48 cuts in each piece of plywood was pretty labor intensive, but the results were great.
Now that we were fully grooved, we decided on the final design and cut the angled bottom of the front panel. This diagonal angle provides visual interest and gives the bats a secure place to land before they climb up the grooves into the box. Next, we cut this front panel into two pieces near the bottom. This allows for a 1/16″ vent for temperature regulation inside the box.
Tip: Have fun with your bat box design! We wanted to keep ours pretty simple since it will be mounted to horizontal vinyl siding.
Building the Walls and Floor
With the front shape finalized, we were able to make the cuts for the vertical ‘walls’ of the box. We used leftover cedar 2’x4′ pieces from our lumber pile and ripped them down on the table saw to a final thickness of about 2″. If a table saw isn’t accessible, 2″ x 2″ lumber would work perfectly here. We then traced the outline of the front panel and cut the bottoms of the walls to match. Next, we stubbed in a ‘floor’ that helps to keep the cavity of the box open, but reduces the size of the opening to deter predators from entering. Remember, bats prefer an opening of around 3/4″. Extra caulk was applied and everything was nailed into place at this point.
Note: The ‘floor’ piece should not be attached to the back panel, where it would block access from the ‘landing pad’. It should be attached to the front of the box to allow the bats free upward motion.
We then applied liberal amounts of caulk to the surface of all cedar shown above and used our air nailer to fasten the front panel (grooves facing in!) and roof onto the box. We also opted to cut cedar side panels (using the optional cedar fence picket) that finish off the box nicely and should help keep drafts from making their way inside. The step is likely unnecessary, but we love the finished look!
Sanding + Finishing
We gave everything a half hour of dry time to allow the caulk to cure, then gave the entire box a thorough sanding. This smoothed things out and provided a uniform surface for stain application.
With construction and sanding complete, it was time to wipe on our stain. We keep a small box of old rags, tattered socks and torn t-shirts on hand for projects like this. Stain can really ruin your day if you’re not careful! We used Minwax Special Walnut for a medium brown finish that will blend nicely into our wooded surroundings.
The last step was to apply two thin coats of matte Polycrylic to protect the wood further. If exterior paint were used in place of stain, this step would be unnecessary.
The Finished Product
Done! The final dimensions ended up around 19″w x 25″h x 4.5″d. This should provide enough cavity space for bats to cling to the interior of the front and back walls while keeping them warm and cozy!
The photo below illustrates our note from above regarding the ‘floor’. Notice how it’s attached to the front panel of the box as opposed to the rear? Remember to maintain vertical access from the landing pad.
The beauty of this design is its potential to be tweaked for simplicity! We added the diagonal cuts for visual interest, but if access to a table saw and miter saw isn’t available, all cuts could be made at 90 degrees with a hand saw. Most big box hardware stores will also cut plywood for free on their panel saw, leaving only the walls, roof and floor to be cut at home.
Happy bat box making and again, Happy Halloween!