What's inside
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A cedar bat house is a manageable first woodworking project: the cuts are mostly straight, the materials are easy to find, and the build can be done with basic tools. The details that matter most are the interior grip, a dark and warm location, and a mounting system that keeps the house stable. This plan uses exterior cedar boards and vertical mounting rails, so the box can be attached to a pole or a suitable flat surface.
Contents
Plan and materials
Make a single-chamber house with an interior width of about 14 inches, a height of 24 inches, and a cavity around ¾ inch deep. That depth gives bats room to roost while discouraging wasps from filling a larger void. Use rough-sawn cedar for the landing area if available; smooth lumber is harder for bats to grip. If your boards are planed smooth, score the inside surfaces with closely spaced horizontal cuts about ⅛ inch deep.
You’ll need ¾-inch cedar for the front, back, sides, roof, and rails; exterior-rated screws; and exterior caulk or wood glue rated for outdoor use. Cedar is naturally rot-resistant, but avoid cedar treated with preservatives. A cedar board search can help you check local sizes and prices. Actual board dimensions are smaller than the nominal size: a 1×8 is typically about ¾ by 7¼ inches, so the back will need to be made from joined boards or cut from wider stock.
Tools and buying choices
A circular saw, drill, tape measure, square, and clamps are enough. A table saw makes the narrow side pieces easier to rip accurately, but it is not essential. For a beginner, the main trade-off is control versus convenience: a circular saw with a straightedge guide is usually cheaper and perfectly adequate for these few cuts. A straightedge guide for a circular saw is useful if you do not own a table saw.
| Choice | Good for | Trade-off |
|---|---|---|
| Exterior screws | Most first-time builders | Easy to install and repair; use corrosion-resistant screws. |
| Staples or brads | Fast assembly with a nailer | May loosen over time; still seal joints and use screws where rails carry the load. |
| Rough-sawn cedar | Grip-ready interior | Can be harder to find and less uniform in thickness. |
| Smooth cedar with scoring | Readily available boards | Requires extra work; shallow or widely spaced grooves may not provide enough grip. |
Cut list
Dimensions below assume a finished interior width of roughly 14 inches. Adjust the front and back widths to match the boards you buy, keeping the cavity at least 12 inches wide and the chamber depth close to ¾ inch.
- Back: 24 inches high, about 14 inches wide, assembled from boards if needed.
- Front: 24 inches high, about 14 inches wide.
- Sides: two strips, 24 inches long by ¾ inch deep.
- Roof: about 16 by 4 inches, with enough overhang to shed rain.
- Mounting rails: two cedar strips, 24 to 30 inches long, at least 1½ inches wide.
Check your actual lumber before cutting. If the side strips are deeper than ¾ inch, the bat house cavity will be wider front to back. That is not a reason to start over, but a cavity much deeper than 1 inch can make the house less suitable for the intended roosting space.
Build the house
1. Cut the back, front, sides, and roof square. Mark the top of each panel to avoid reversing parts during assembly. On the inside face of the back, cut horizontal grooves from near the bottom to within about 2 inches of the top. Space them roughly ¼ inch apart. Add similar grooves to the inside face of the front panel.
2. Lay the back flat. Run a thin bead of exterior glue along each side strip, position the strips along the back’s long edges, and fasten them with exterior screws. Drill pilot holes near board ends to reduce splitting; cedar is soft, but screw tips can still split narrow strips. Use screws about every 6 inches.
3. Place the front panel over the sides and fasten it the same way. Leave the bottom open for the landing area. Do not caulk the bottom edge shut: trapped water can soak the interior and lead to rot.
4. Fasten the roof across the top, with a modest overhang at the front and sides. Seal the top and side joints with exterior caulk, but keep the interior free of paint, stain, and caulk. A small gap at an upper edge can admit rain; an unsealed bottom is intentional drainage.
5. If you want added protection, paint or stain only the outside with a dark, non-toxic exterior finish, keeping it off the landing surface and interior. Dark finishes can help absorb heat in cooler climates, but they may overheat a box in hot, sunny locations. Leave the surface unfinished if local conditions are warm or you are unsure.
Add the mounting rails
Attach one rail vertically to each outer edge of the back, using screws long enough to pass through the rail and into the back without entering the cavity. Keep the rails flush with the back’s outer edges. They create a gap behind the box, help reduce direct contact with a mounting surface, and give you solid points for fastening. Predrill the rails and use at least three screws per rail, spaced along the height.
Mount the rails to a sturdy post or wall with galvanized or stainless exterior fasteners. For a post, use two horizontal straps or appropriately long structural screws through the rails; don’t rely on a single screw at the top. A search for exterior structural screws can help you compare lengths and coatings. The cheaper general-purpose drywall screw is a poor choice outdoors: its coating can fail, and its brittle shank may snap under movement.
Choose a location and check the result
Choose a warm, sunny location that is protected from strong prevailing wind, often on a pole or the side of a building. A height of 12 to 20 feet is commonly used, but secure access for installation matters more than chasing an exact number. Keep the entrance clear of branches and other obstructions, and do not place the house where people, pets, or predators can easily reach it. Local wildlife groups may offer region-specific placement advice.
Before hanging it, check that the box is rigid, the rails do not wobble, and the cavity is close to ¾ inch deep. Look for protruding screw points, open side seams, and a roof that sheds water away from the entrance. A poorly sealed side joint can let in rain; an overly smooth interior can leave bats unable to climb; and a loose mount can sway enough to discourage use. Do not open or disturb an occupied bat house. Give a new house time, and remember that careful construction improves the odds but cannot guarantee that bats will move in.