Plan it
Board cut schedule
Every panel you'll need to cut, sized to actual milled lumber dimensions. Print this page or download the PDF to take into your workshop.
| Panel | Dimensions | Qty | Notes |
|---|---|---|---|
| Back | 11.25″ × 30″ | 1 | Score horizontal grooves every 1/2 inch to provide a grip for bats; bottom 10 inches serves as a landing strip. |
| Front | 11.25″ × 20″ | 1 | Score the interior side horizontally; leave a 1/2 inch gap near the bottom for ventilation. |
| Side | 1.5″ × 20″ | 2 | These act as spacers between the front and back to create the 0.75 inch roosting chamber. |
| Roof | 11.25″ × 6″ | 1 | Angle the top edges of the front and sides 15 degrees for a sloped, rain-shedding roof. |
| Floor | 11.25″ × 1″ | 1 | Attach as a bottom reinforcement slat across the front, leaving the 0.75 inch entrance slot open. |
Source board layout
All panels are cut from the 1x12 board. The two 1.5-inch side spacers are ripped from the remaining length after the front and back are cut. Horizontal scoring for grip is essential on all interior surfaces.
Get materials
Shopping checklist
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Build it
Construction notes
- Wood: 3/4-inch (19 mm) untreated cedar or rough-sawn plywood. Never use pressure-treated wood.
- Boards: A single 1" x 12" x 8' untreated cedar board provides enough material for the house and internal spacers.
- Hardware: 25x 1-5/8" galvanized deck screws, 1x quart dark water-based exterior stain, 1x tube exterior-grade non-toxic caulk, 2x 3" lag bolts for mounting, 1x roll 1/8" plastic bird netting (optional alternative to scoring)
- Ventilation: Leave a 1/2-inch horizontal gap between the front panel and the bottom reinforcement slat to allow airflow.
- Drainage: The bottom is an open slot, so water naturally sheds; ensure the roof joints are caulked to prevent leaks.
- Predator guard: Mount the house at least 12 feet high on a smooth metal pole or a flat building surface to prevent cats and raccoons from reaching the entrance. Avoid mounting on trees, as branches provide easy perches for owls and climbing paths for snakes.
Install it
Place it & time it right
Mount on a pole or the side of a building to avoid shade and predator access from tree branches. Ensure the house is within 1,500 feet of a water source like a pond or stream and at least 20 feet from the nearest tree canopy.
Seasonal timeline
When to install
Install in late winter or very early spring, before the bats emerge from hibernation in March or April.
Nesting begins
Maternity colonies typically form in April in the Midwest and Northeast. In the Northwest and West, bats may begin occupying roosts as early as March depending on local temperatures.
Eggs & incubation
1 pup (usually born in June) · 50-60 days (gestation)
Fledging & cleaning
3-4 weeks after birth · Unlike bird boxes, bat houses do not need annual cleaning. Guano falls out the bottom, and bats prefer the seasoned scent of an established roost.
Regional considerations
The Little Brown Bat is found throughout most of North America, from the subarctic regions of Canada and Alaska down through the United States to the high-elevation forests of the Southwest.
Roosting begins earlier in warmer coastal climates and later in high-altitude mountain ranges or the far North. Early spring warmth is the primary trigger for bats moving from hibernacula to summer maternity boxes.
The main threats are Great Horned Owls at the entrance and raccoons climbing from below. High mounting heights and smooth pole surfaces are the best defenses against these threats.
Add a camera
Watch it happen
Because Little Brown Bats are nocturnal and highly sensitive to light, interior monitoring requires a high-quality infrared (IR) camera with no visible 'red glow' LEDs. Mount a small, flat-profile USB camera at the very bottom of the chamber, looking straight up. This provides a clear view of the maternity cluster and growing pups clinging to the ceiling without disturbing their sleep cycle.
For exterior observation, a wide-angle outdoor camera should be positioned 4 to 6 feet directly below the bottom entrance slot. This is the best way to capture the spectacular 'emergence' at dusk when bats drop into the air to hunt. Using a camera with a high frame rate will help capture the fast-moving bats clearly as they exit.
Route all camera cables tightly along the exterior of the house and down the mounting pole using weatherproof clips. It is vital that no loose wires are inside the chamber, as bats can easily become entangled. For AI-powered counting, ensure the camera's motion zone is focused on the bottom 6 inches of the landing strip.
A dedicated trail camera or an outdoor security camera like a Blink can be mounted on a nearby structure to monitor the perimeter for predators. This secondary view helps you identify if owls or climbing mammals are showing interest in the colony, allowing you to adjust predator guards if necessary.
Off-grid power with a USB solar panel
Nest boxes are almost always far from a power outlet. A 5V USB solar panel with a built-in battery is the cleanest solution — it powers most interior USB cameras, Blink cameras (via their USB port), and many trail cameras indefinitely.
- Panel position: Mount on the same post as the box, 1–2 ft above, angled 30–45° from vertical and facing south.
- Cable routing: Run inside split loom or 1/2″ conduit so squirrels can't chew it. Enter through the same grommeted hole as the camera cable.
- Battery buffer: Pick a panel with a 5–10 Ah battery so the camera runs through cloudy days and overnight for nocturnal species.
- Weatherproofing: Wrap every cable connection in self-amalgamating rubber tape.
Troubleshoot
Common problems & solutions
Bats not using the box
Ensure the box receives at least 6 hours of sun; move it to a location with better solar exposure if it remains empty for two seasons.
Wasps building nests inside
The 0.75-inch slot width is designed to deter most birds and larger wasps, but if they persist, ensure the interior is rough but clean of old mud.
House getting too hot
In very hot climates, add a second ventilation slot or paint the house a lighter shade of brown rather than black.
Wood warping or splitting
Use exterior-grade caulk on all joints during assembly and apply a high-quality water-based stain to the exterior only.
Common questions
Frequently asked questions
Bats do not use a hole but rather a bottom entrance slot. For Little Brown Bats, this slot should be exactly 0.75 inches (19 mm) wide to keep out larger predators and competitors.
The box should be mounted 12 to 20 feet (3.6 to 6.1 meters) above the ground. This height is necessary to give the bats enough space to 'drop' into flight and to keep them safe from ground predators.
The best time is late winter or early spring (January to March). This allows the house to 'weather' and be ready for female bats looking for maternity roosts when they emerge from hibernation.
In most northern and temperate regions, it should face South or Southeast. This maximizes solar heat gain, which is critical for the survival and growth of the pups inside.
Maintaining a tight 0.75-inch entrance gap is the best deterrent. If wasps become a persistent problem, you can try rubbing unscented bar soap on the interior ceiling where they usually start their nests.
Little Brown Bats only have one 'brood' per year, consisting of a single pup. This low reproductive rate is why providing safe maternity roosts is so important for their conservation.
You generally do not need to clean them out. The bottom-opening design allows guano to fall to the ground, and bats prefer houses that have been occupied before and carry the scent of the colony.
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