What a birdhouse plan sheet shows
A plan sheet here is a single page that carries everything needed to cut one box: a front elevation with the hole, a side section with the interior depth, and a cut list that names each part, its size and the board it comes from. The drawings and the table are generated from one set of numbers, so they cannot disagree. A switch above the drawings changes all labels between inches and millimeters.
The dashed line on the front elevation is the floor level inside the box. The dashed frame is the band in which the center of the entrance hole may sit, measured up from that floor. The side section dimensions the interior depth, from floor to the underside of the roof.
Each sheet sits on its own page, with the sources for its figures, the features every box needs and a short note on how the numbers were set. The wider picture, including how entrance sizes keep House Sparrows and starlings out, is on the birdhouse plans and placement page.
The three boxes compared
| Box | Entrance | Floor | Interior depth | Mount height |
|---|---|---|---|---|
| Eastern bluebird house plans | 1 1/2 in | 5 1/2 x 5 1/2 in | 9 in | 4 to 6 ft |
| Black-capped chickadee house plans | 1 1/8 in | 5 1/2 x 5 1/2 in | 8 in | 5 to 15 ft |
| House wren house plans | 1 in | 5 1/2 x 5 1/2 in | 8 in | 5 to 10 ft |
All figures come from the Cornell Lab NestWatch species pages. Entrance height above the floor is not in the table because it is the one dimension where sources differ: the sheets draw it as a range, 6 to 8 inches for the bluebird and chickadee and 4 to 6 inches for the wren.
Choosing a box for the bird in view
The bird decides the box, and the habitat decides the bird. A pole in an open field or on a lawn beside open woodland suits the eastern bluebird, which NestWatch pairs with grassland and open woodland and a mount of 4 to 6 feet. A box on a tree or building wall in a wooded yard or town suits the black-capped chickadee, which accepts anything from 5 to 15 feet. A yard with shrubs and woody cover close by suits the house wren, with the box within 100 feet of that vegetation and 5 to 10 feet up.
The hole is the main filter. A 1 inch hole admits a wren and little else; 1 1/8 inches admits a chickadee; 1 1/2 inches admits a bluebird. A hole larger than the plan shows will let in birds the box was not built for, so the sheets never make the entrance size adjustable. Anyone uncertain which species nests nearby can look at which small birds visit a feeder in spring, and then pick the plan that matches.
Lumber for the plans
Every plan is built from two ordinary boards. By the Southern Pine Inspection Bureau, a 1x6 measures 3/4 by 5 1/2 inches actual and a 1x8 measures 3/4 by 7 1/4 inches. The 3/4 inch thickness also meets the wall minimum NestWatch states. The sides and floor come from a 1x6 at its full width. The front and back are 7 inches wide, which means ripping a 1x8 down by a quarter inch.
Lumber lengths are listed before saw kerf, at the foot of each cut list. The bluebird box takes about 24 inches of 1x6 and 18 1/2 inches of 1x8; the chickadee and wren boxes take about 22 inches of 1x6 and 16 1/2 inches of 1x8.
How these figures were set
Entrance hole, floor, interior depth and mount height come from NestWatch species pages. Lumber widths come from the Southern Pine Inspection Bureau. Panel sizes are arithmetic on those figures for one standard construction: sides between front and back, 3/4 inch boards, floor recessed 1/4 inch. The roof is not dimensioned. Conflicting sources are shown as ranges. Boxes perform differently by region, and a local nest-box program may advise changes. Reviewed 2026-10-06.
Common questions
What is on a plan sheet?
A front panel drawing, a side section and a cut list, all computed from the same sourced figures, with a switch between inches and millimeters.
Why do all three boxes share a 5 1/2 inch floor?
That is the floor NestWatch gives on each of the three species pages. Smaller floors published by some state agencies are minimums that it also satisfies.
Do the plans include a roof?
No. The roof is not dimensioned; the overhang rule is stated instead, 2 to 4 inches at the front and 2 inches at the sides.
Which lumber do the plans use?
Ordinary 1x6 and 1x8 boards. A 1x6 is 3/4 by 5 1/2 inches actual and a 1x8 is 3/4 by 7 1/4, according to the Southern Pine Inspection Bureau.
Why is the entrance height drawn as a range?
Where sources disagree, the sheet shows the band in which every stated height fits. The wren is the exception in that two agencies agree on 4 to 6 inches.