How to Make a Bird House
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Learning how to make a bird house is mostly a matter of getting a few measurements right, and the sources agree on most of them. This guide covers a bluebird box, because the NABS and NestWatch figures are written for that box. The points that matter most are the wood, the entrance hole, the roof, the drainage, the access door and the predator guard. Where the sources give different numbers, this guide shows each one.
Quick answer
- Use untreated, unpainted wood or exterior grade plywood, never pressure-treated plywood, and fasten it with galvanized screws or nails.
- Drill a 1 9/16 inch round entrance, about 4 1/2 to 6 inches above the floor, with a rough or grooved surface below it.
- Build a roof that overhangs the front and sides, add drainage holes and vents, and make one panel open for cleaning.
- Mount the box on a pole with a predator guard, since the sources treat a guard as a key protection against climbing predators.
Choose wood and fasteners that will last
NestWatch recommends untreated, unpainted wood, preferably cedar, pine or cypress. The NABS recommendations say solid wood about 3/4 to 1 inch thick works well, and that exterior grade plywood made with water-resistant glue is also suitable if it is sealed. The NABS FAQ says redwood often splits as it dries, and that most pine boards will warp over time, so the choice of wood is a trade-off between weather and stability.
Some materials are ruled out. The NABS recommendations say pressure-treated plywood must not be used, because some preservatives could be toxic to birds, and they list flimsy materials such as cardboard as easily destroyed by weather and predators. Metal overheats in hot weather, and clay or ceramic breaks and holds heat.
Fasteners matter for the seal. NestWatch’s advice is short: “Use galvanized screws for the best seal.” It adds that “Nails can loosen over time,” which can let rain into the box. Screws are also easier to remove for repairs, and NestWatch advises against staples. The NABS FAQ accepts screws or galvanized nails, and it notes that screws cost more but make building and later repairs easier.
Know the measurements the sources give
The table below collects the figures for a bluebird box from the NestWatch features page and the NABS recommendations and plan. Where the sources differ, every value is shown.
| Feature | Figure the sources give | Source |
|---|---|---|
| Entrance hole | 1 9/16 inch round works for all three bluebird species | NABS recommendations |
| Floor size | 4 by 4 to 5 1/2 by 5 1/2 inches | NABS recommendations |
| Entrance to floor | 4 1/2 to 6 inches | NABS recommendations |
| Wall thickness | At least 3/4 inch | NestWatch features |
| Floor recess | At least 1/4 inch (NestWatch); 1 inch (NABS recommendations feature list); 3/4 inch (NABS plan) | Three sources |
| Drainage | At least four 3/8 to 1/2 inch holes (NestWatch), or 1/4 to 1/2 inch holes or cut corners (NABS) | Two sources |
| Vent holes per side | Two 5/8 inch holes (NestWatch); three 3/8 inch holes (NABS recommendations); three 1/2 inch holes (NABS plan) | Three sources |
| Front roof overhang | 2 to 4 inches (NestWatch features); 3 to 5 inches (NABS recommendations); about 6 to 6 1/2 inches (NABS plan); five inches (NestWatch predator page) | Four sources |
| Side roof overhang | 2 inches | NestWatch and NABS |
The vent and roof figures disagree the most, so a builder who follows one page will get a different box from one who follows another. The draft does not choose a winner, because none of the sources explains why its figure suits every site.
Cut the walls, floor and roof
The NABS plan’s materials list calls for standard 1 inch boards, with 6-inch widths for the body and a 10-inch board for the roof, plus about twenty galvanized nails or 1 5/8 inch deck screws. The plan suggests a cut order: start with the floor piece and work toward the back piece, because the back length is the least critical measurement.
The plan also calls for two pivot screws for the door and one holding nail, a double-headed nail about 1 1/2 to 2 1/2 inches long. Pivot points let the door swing open for monitoring. Pre-drill the holes so the boards do not split. The plan says to drill 3/16 inch holes for the outside screws and 1/8 inch holes into the inside board.
The walls need to hold heat. NestWatch asks for at least 3/4 inch thickness and notes that boards sold as 1 inch are actually 3/4 inch thick. Check the real thickness with a rule before you cut, since the label on a board is not always its true size.
Build the roof so rain runs off
The roof is where the sources most often describe the same goal in different numbers. NestWatch asks for a sloped roof that overhangs the front by 2 to 4 inches and the sides by 2 inches, and it adds 1/4 inch deep cuts under the roof on all three edges to channel water away. The NABS recommendations ask for a roof that extends 2 inches on each side and 3 to 5 inches in front, with more being better. The NABS plan describes a front overhang of about 6 to 6 1/2 inches and a 20 degree slope from back to front.
Some roof choices are ruled out. NABS says a single sheet of plexiglass or a galvanized metal roof is not recommended because of overheating, and that a box with a hole through the roof is not recommended because the contents are too exposed to weather and predators. Plastic, Hardie Board or roofing shingles can work, if there is sufficient insulation underneath.
The roof should cover the back edge of the box, unless other features keep rain out of the back joint. NABS also asks for tight seams, sealed with exterior grade silicone or latex caulk, and for floor drainage through corner cuts or small holes.
Drill the entrance, vents and drainage before assembly
The NABS plan says to drill the ventilation and entrance holes before you assemble the box. Vent holes drilled at an upward angle reduce the problem of water entering the box, according to the NABS recommendations. The plan says three 1/2 inch holes on each side, just below the roof, can be drilled safely with a 10-inch roof and about 2 inches of overhang. The NABS recommendations describe three 3/8 inch holes per side under the eaves, and NestWatch describes two 5/8 inch holes per side near the top. The sources do not agree on the size, so check the vent figure against your own roof before you drill.
Smooth the entrance with sandpaper after drilling. The NABS plan says to chisel the sides flat if you cut an oval entrance. The NABS recommendations accept a 1 9/16 inch round hole for all three bluebird species, and the plan notes that the same hole also works for Eastern bluebirds.
The inside of the front wall needs a rough surface below the entrance so young birds can climb out. NABS recommends cutting shallow saw kerfs in a horizontal line, like a ladder, if the wood is smooth, and it says the distance from the bottom of the entrance to the floor should be between 4 1/2 and 6 inches. It advises against hardware cloth as a climbing surface, because birds can catch their feet in it. NestWatch describes the same idea as rough or grooved interior walls.
Drainage comes last. NestWatch says to add at least four drainage holes of 3/8 to 1/2 inch in the floor, or to cut away the corners of the floorboard. NABS recommends cutting dog-ears at each corner or drilling 1/4 to 1/2 inch holes in the floor. Both sources ask for a recessed floor so the nest stays dry, though they disagree on the depth, as the table shows.
Make the front open for cleaning
A box you cannot open is a box you cannot clean or monitor. NABS says all nestboxes must be openable from the side, front or top, and that a bottom opening box should not be used. NestWatch lists a hinged side with a sturdy latch as a feature of a good birdhouse, and it says a latch or nail keeps the box closed until you are ready to open it. The NABS recommendations say the cleanout door should have a pivot point at the top or bottom, so that it opens without disturbing the nest.
The door needs something to hold it shut. NABS recommends a screw or a down-angled nail in a pre-drilled hole. If vandalism is a concern, NABS suggests galvanized screws that need an uncommon bit. The NABS plan adds a hole drilled through the front board and the side of the door, so a nail holds the door closed.
Extend the back panel for mounting
Plan the back before you assemble the box. NestWatch says a few extra inches at the top and bottom make it easier to mount the box on a metal pole. NABS recommends extending the back panel below the box body, so the box can be attached to the pole with screws, nails, pipe hangers, wire or U-bolts. For the pole itself, NABS recommends a smooth, sturdy support, such as half to three-quarter inch electrical metal conduit, or a T-post with 1 1/2 inch conduit on top.
If you want a simpler project first, our guide to a DIY bird feeder made from a plastic bottle covers a feeder, not a nest box, so the measurements in this guide do not apply to it. For ready-made bluebird boxes, see our roundup of bird houses for bluebirds.
Add a predator guard
The box needs protection once it is on a pole. NestWatch describes three time-tested options: cone baffles, stovepipe baffles and Noel guards. A cone baffle is a metal collar about 3 feet in diameter around the pole below the box. A stovepipe baffle is generally about 8 inches in diameter and 24 to 36 inches long. A Noel guard is a wire mesh tube on the front of the box, which NestWatch says to use with another guard or on boxes installed on trees.
NABS gives more detail for homemade versions. Its predator factsheet describes a Zeleny cone cut from a 3-foot circle of galvanized sheet metal, with a center hole sized to the post. It also describes a PVC baffle made from 4-inch thin-wall PVC at least 2 feet long. The baffle must swing freely on the pipe, so that it wobbles when a raccoon or cat tries to climb. The same factsheet describes a Noel guard as a rectangle of 1/2 inch hardware cloth placed around the entrance hole.
A guard works only if it can do its job. NABS says the PVC baffle must wobble to discourage climbing, and that sheet metal wrapped around a wooden post should extend at least 3 feet below the box. NestWatch’s predator page adds that a roof extending five inches beyond the front keeps animals from reaching into the entrance from above.
Finish the surfaces with care
Natural or unpainted wood is fine for cedar and redwood, which weather well, according to NABS. If you paint or stain a box, the NABS recommendations ask for nontoxic products, such as water-based latex paint, raw linseed oil or a wood sealer, and for light colors such as earth tones or white to reflect sunlight. The NABS plan says not to paint the outside of the front panel, the one with the entrance hole. The general rule is that the inside of the box should not be painted.
Build with safety in mind
The sources do not list tools. Their one safety point is that anyone building a nest box should use all appropriate safety equipment, including respiratory and eye protection.
How we chose
Our basis is the NestWatch features and predator pages and the NABS recommendations, FAQ, plan and predator factsheet, all opened on 2026-10-22. Each figure in the draft comes from one of those pages, and the table shows each value with its source where the pages differ. We left out retail plans, product pages and blog builds. The NABS recommendations say the organization “no longer approves specific nestbox designs”, so the draft does not describe any plan as the approved one.
What we could not verify
We did not build a box, cut a board or test any dimension, so the draft reports what the sources say and nothing more. The NABS plan’s printed dimensions did not extract cleanly from the PDF, so the draft uses the plan’s materials and drilling steps and avoids the cut-list figures that were not legible in our copy.
The sources also do not say how long a bird house made from untreated wood will last outdoors, or how the wood species sold in a given area compare. They do not give a vent size or roof overhang that suits every climate, and NABS notes that vent holes may not be appropriate where gnats are a serious problem or in colder northern climates.
What the sources do not say
No source opened gives a single correct roof overhang, vent size or floor recess depth for all sites. The sources also do not give a total cost or a build time, and local rules on nest boxes and predator control are not covered.
Frequently asked questions
Should a bird house use screws or nails?
Galvanized screws are the better choice for the seal, according to NestWatch, because nails can loosen over time and let rain in. NABS accepts galvanized nails as well as screws, and it says screws make repairs and tightening easier.
Does a bird house need a perch?
No. NABS says perches should never be used on bluebird nestboxes, because the birds do not need them and House Sparrows use them to harass nesting birds. NestWatch adds that a perch can help predators reach the box.
Can pressure-treated wood be used for a bird house?
No, according to the NABS recommendations. They say pressure-treated plywood should not be used, because some preservatives could be toxic to birds. The NABS FAQ also advises against treated lumber and interior grade wood, including OSB.
What size hole should a bluebird house have?
NABS says a 1 9/16 inch round hole is acceptable for all three bluebird species, and NestWatch gives 1 1/2 inch round for Eastern bluebirds. Where the species overlap, NABS says to use the larger opening.
Does a bird house need a predator guard?
Where climbing predators such as raccoons, cats or snakes live, the NABS recommendations say the nestbox needs a predator-resistant device. Options include a wobbling baffle, a Noel guard or a waxed metal pole. NestWatch describes cone baffles, stovepipe baffles and Noel guards as its three options.
Sources
- https://nestwatch.org/learn/all-about-birdhouses/features-of-a-good-birdhouse/ (opened 2026-10-22)
- https://nestwatch.org/learn/all-about-birdhouses/dealing-with-predators/ (opened 2026-10-22)
- https://www.nabluebirdsociety.org/PDF/NABS%20factsheet%20-%20Nestbox%20Recs.pdf (opened 2026-10-22)
- https://www.nabluebirdsociety.org/PDF/NABSFactsheetFAQs.pdf (opened 2026-10-22)
- https://www.nabluebirdsociety.org/PDF/NABS%202020%20Eastern%20-Bluebird%20Nestbox%20Plans.pdf (opened 2026-10-22)
- https://www.nabluebirdsociety.org/PDF/NABSFactsheetPredatorControl.pdf (opened 2026-10-22)
