Birdhouse Dimensions
A bluebird house needs a floor of about 5 × 5 in (127 mm) inside, 8–12 in of height and a 1 1/2 in (38 mm) entrance hole about 6 in above the floor. Wrens and chickadees take a smaller house: a 4 × 4 in floor and a 1 1/8 in (29 mm) hole. The hole size matters most: a hole just big enough for the bird you want keeps bigger birds out.
Birdhouse dimensions chart
| Bird | Inside floor | Inside height | Hole diameter | Hole above floor | Mount height |
|---|---|---|---|---|---|
| Eastern bluebird | 5 × 5 in (127 mm) | 8–12 in | 1 1/2 in (38 mm) | 6–7 in | 5–10 ft |
| Mountain bluebird | 5 × 5 in (127 mm) | 8–12 in | 1 9/16 in (40 mm) | 6–7 in | 5–10 ft |
| Tree swallow | 5 × 5 in (127 mm) | 6–8 in | 1 1/2 in (38 mm) | 5 in | 5–15 ft |
| House wren | 4 × 4 in (100 mm) | 6–8 in | 1 1/8 in (29 mm) | 4–6 in | 5–10 ft |
| Carolina wren | 4 × 4 in (100 mm) | 6–8 in | 1 1/2 in (38 mm) | 4–6 in | 5–10 ft |
| Chickadee | 4 × 4 in (100 mm) | 8–10 in | 1 1/8 in (29 mm) | 6–8 in | 5–15 ft |
| Titmouse | 4 × 4 in (100 mm) | 10–12 in | 1 1/4 in (32 mm) | 6–10 in | 5–15 ft |
| White-breasted nuthatch | 4 × 4 in (100 mm) | 10 in | 1 1/4 in (32 mm) | 7–8 in | 12–20 ft |
| Downy woodpecker | 4 × 4 in (100 mm) | 8–10 in | 1 1/4 in (32 mm) | 6–8 in | 6–20 ft |
| Purple martin (one room) | 6 × 6 in (150 mm) | 6 in | 2 1/8 in (54 mm) | 1–2 in | 10–20 ft |
| Northern flicker | 7 × 7 in (180 mm) | 16–18 in | 2 1/2 in (64 mm) | 14–16 in | 6–20 ft |
| Screech owl, kestrel | 8 × 8 in (200 mm) | 12–15 in | 3 in (76 mm) | 9–12 in | 10–30 ft |
These are the sizes most bird societies recommend; birds are not strict about the inside height, but they are about the hole. Purple martins nest in colonies, so they need a house with many rooms on a tall pole, not a single box.
Bird house hole size
The entrance hole decides which birds move in, and different birds need different sizes:
- 1 1/8 in (29 mm): house wrens and chickadees. Too small for house sparrows.
- 1 1/4 in (32 mm): titmice, nuthatches and downy woodpeckers.
- 1 1/2 in (38 mm): eastern bluebirds, tree swallows and Carolina wrens. House sparrows fit too, starlings do not.
- 1 9/16 in (40 mm): mountain and western bluebirds.
Drill the hole with a spade bit or a hole saw before assembly, and cut a few shallow grooves inside the front below it so the young birds can climb out.
Details every birdhouse needs
- Drainage: clip the corners of the floor or drill four 6 mm (1/4 in) holes, and set the floor 6 mm up inside the walls so the end grain stays dry.
- Ventilation: two or three holes, or a 6 mm gap, under the roof on each side.
- A roof that overhangs the front by 2–3 in (50–75 mm) keeps rain out of the hole.
- A side that opens for cleaning after each brood: two pivot nails at the top and a screw at the bottom.
- Bare wood inside: untreated cedar or exterior plywood 3/4 in (18 mm) thick, never pressure-treated wood, and no paint or stain inside.
Building a birdhouse
Our birdhouse plan builds the classic bluebird box above: a back that doubles as the mounting board, sloped sides, a recessed floor and an overhanging roof. Type the floor size and the front height from the chart, and every part follows. It covers every bird in the table up to a 7 in floor; owls, kestrels and flickers need a bigger box.
Frequently asked questions
What size hole does a blue bird house need?
1 1/2 in (38 mm) for eastern bluebirds and 1 9/16 in (40 mm) for mountain bluebirds, with the bottom of the hole about 6 in (150 mm) above the floor.
What hole size keeps sparrows out?
A 1 1/8 in (29 mm) hole keeps house sparrows out, which suits wrens and chickadees. Bluebird holes are big enough for sparrows, so watch bluebird boxes and remove sparrow nests.
How high should a birdhouse be mounted?
About 5–10 ft (1.5–3 m) for bluebirds, wrens and chickadees, on a post with a baffle rather than on a tree, which cats and raccoons climb.
Should a birdhouse have a perch?
No. Cavity-nesting birds do not need one, and a perch helps predators and house sparrows reach the nest.