How to Build a Duplex Condo Birdhouse

Updated on October 5, 2017
Anthony Altorenna profile image

Anthony enjoys spending time in the workshop, the kitchen, the garden and out fishing. Many of his projects are featured in his yard.

Birdhouse Condo Plans
Birdhouse Condo Plans | Source

Duplex Condo Birdhouse Plans

Birdhouses are fun and easy projects to build, and you get a warm feeling of satisfaction from watching a pair of birds raise their family in a birdhouse that you built yourself. I've made hundreds over the years and at last count, I have over 30 different birdhouses hanging in the garden and spread out around our yard. Handmade birdhouses make great gifts, and I've given away many to families and friends. I also sell a few online.

After building lots of basic nest boxes, I started looking for ways to make birdhouses that are more fun and interesting to look at, yet are still functional and will attract a variety of cavity nesting birds. Though they vary in shape and size and some sport unique and decorative details, they all must have one important element in common: every birdhouse is built for the birds.

Hanging Duplex Condo Birdhouse
Hanging Duplex Condo Birdhouse | Source

How to Build a Condo Birdhouse

Building a duplex condo that the birds will actually use starts with understanding the basic nesting needs of the birds in your area. Made with the needs of the birds in mind, my birdhouses have fledged many generations of birds. With separate nest boxes and an entrance on either end, this birdhouse is designed to attract a variety of small cavity-nesting birds including chickadees and wrens.

The birdhouse condo is easy to make from expensive pine. The exterior is stained to help protect the wood from the elements and to add a rustic charm. The stained pine will last for several seasons of sun, rain and snow. Designed to sit on top of a post or to hang from a cable, the condo features a divider in the middle of the interior to separate the space into two individual nesting areas.

Utah License Plate Condo Birdhouse
Utah License Plate Condo Birdhouse | Source

The duplex condo in the first photo looks basic and bland. And it is. The long sides were sized to fit an old license plates, and you can attach one to either side. It is also a blank canvas for painting or adding bits of whimsy and other details that will make each birdhouse interesting and unique.

I bought the used license plates at a local flea market for just a few dollars each. I designed the side dimensions of the condo birdhouse based on the size of a license plate. The colorful plates makes each birdhouse unique, and I think it looks pretty cool.


The Cutting List

I use pine to build many of my birdhouses. The local home center sells short sections of pine in various widths at reasonable prices, and I also used several pieces that I collected in my scrap bin. Pine takes stain well, the total cost was less than $10, and the birdhouses that I've made from pine have lasted almost as long the birdhouses made from cedar and redwood. Birdhouses are good projects for using leftovers and scraps including pieces of hardwood and reclaimed lumber. Besides making interesting birdhouses, scraps and leftovers are free!

Cut the boards of your choice into the following dimensions:

  • Sides: 10-5/8" L x 5-12" W (quantity = 2)
  • Ends: 8-3/4" L x 5-1/2" W (quantity = 2)
  • Floor: 10-5/8" L x 4" W
  • Divider: 8" L x 4" W
  • Roof A: 14" L x 5-1/4" W
  • Roof B: 14" L x 4-3/4" W
  • Entrance Guards: 3-1/4" x 3-1/4" (quantity =2)

A Miter Box makes quick work of cutting the angled peaks for the roof
A Miter Box makes quick work of cutting the angled peaks for the roof | Source

The Ends and the Divider

The top of each end section and the divider is cut at a 45-degree angle to support the roof. The steep roofline helps to shed the rain and the roof's overhang protects the vent openings underneath for air circulation to help keep the interior from overheating in the hot sun.

Cut the ends to length, measure and mark the center point of the top edge, and then cut the peak cut at a 45-degree angle. I use a power miter box saw, but a handsaw or jigsaw will also work.

Cut the peak of the divider at the same 45-degree angle. The exact length of the divider may need to be trimmed to fit properly under the roof. I trimmed the divider to the exact length later in the assembly process.

Entrance Layout
Entrance Layout | Source

Making an Entrance

Lay out the locations for the entrance hole on each of the end pieces. Measure down 3-1/2" from the tip of the peak and centered in the middle of the side piece. Drill the entrance holes in the end sections using a 1-1/2" diameter bit.

The entrance guard adds a bit of detail to the ends of the birdhouse, and helps to protect the baby birds from predators reaching inside. The guard is cut from a 3-1/4" square with another 1-1/2" hole drilled through the center. To find the center of the square quickly, line up a ruler on the diagonal across two opposite corners, and make a pencil mark near the center. Then, line up the straight edge across the opposite two corners, and draw another line near the center. The resulting "X" marks the exact center of the square.

I used a 1-1/2" diameter Forsner bit to drill the holes in each of the pieces.

Drilling the 1-1/2" Entrance Hole using a Forsner bit.
Drilling the 1-1/2" Entrance Hole using a Forsner bit. | Source

Size Matters!

One of the most critical elements of building a bird-friendly birdhouse is the size of the entrance hole. If the hole is too small, birds cannot enter the nest box. If the diameter of the hole is too large, smaller birds might be forced out by the larger more aggressive and undesirable birds such as starlings.

Small cavity nesting birds such as chickadees can fit through a 1-1/4" entrance hole. Eastern bluebirds prefer a 1-1/2" entrance, while western bluebirds need a 1-9/16" opening. Any larger than a 1-9/16" hole invites the undesirables to enter.

Bottom view of the drainage holes
Bottom view of the drainage holes | Source

Let the Rain Out and the Air In

Drainage holes are important for letting rainwater to drain out of the nesting areas. You can drill a few holes through the floor, though I prefer to clip off the corners. Cutting away the corners of the floor section allows any rainwater to drain away, while also increasing the air circulation inside the nest box by drawing cooler air in through the floor and out through the openings under the roof line.

Basic joinery makes assembly easy
Basic joinery makes assembly easy | Source

Some Assembly Required

Simple joinery makes it easy to assemble the birdhouse using water-resistant glue with weather-resistant nails and screws. Start by dry fitting the end pieces together with the floor and one of the long sides to ensure that all of the pieces will line up correctly. Use the photo (above) as a guide.

Make any adjustments as necessary. If the fit looks good, fasten one end piece to the side section (I use water-resistant glue and weather-resistant nails). Attach the other end piece to the side section, then attach the floor section to the sub-assembly.

Test fit the divider section against the inside of an end piece. If the tips of the peaks do not line up evenly, mark and cut the bottom of the divider to fit. Once you are satisfied with the fit, position the divider in the middle of the floor section as shown in the photo (above). Attach the divider with glue and by nailing through the bottom and through the side and into the divider.

Side view of the interior
Side view of the interior | Source

Add the Backside

The back piece is held in place with screws that are easily removed for access to the inside of the nest boxes. Position the back piece in place and attached with screws.

Removing the back section for cleaning or for mounting the birdhouse on top of a post is as easy as backing out the screws.

Top view of the interior
Top view of the interior | Source

The Finishing Touches

Now is the time to consider how you want to finish your birdhouse. Painting or staining helps to protect the pine from the elements, and will help the birdhouse to last longer. I find that it is much easier to paint or stain the roof and guard pieces before attaching them to the rest of the partially assembled birdhouse. I like to stain the the roof sections and the entrance guards in a contrasting yet complimentary color from the nest box. I used a pickling white for the body, and walnut brown stain for the roof and entrance guards.

Sand all of the edges to round over the corners and smooth the joints. Breaking the sharp edges allows the paint and stain to adhere better, and gives the birdhouse a finished look. After sanding, paint or stain the exterior of the birdhouse. I only stain the exterior, leaving the interior natural for the safety of the baby birds. Let the pieces dry completely.

The finished condo duplex birdhouse. Note how the wider roof section overlaps the narrower piece to form the peak.
The finished condo duplex birdhouse. Note how the wider roof section overlaps the narrower piece to form the peak. | Source

Raising the Roof

Position the roof sections together by lining up the long edges. The wider piece overlaps the narrower section, forming a 45-degree peak. When set on top of the birdhouse, the roof overhangs each side equally. Attach the roof sections together with more glue and nails.

Line up the holes of the entrance guards with the holes in either side. I like to align one corner of the guard with the peak of the roof, forming a diamond shape. Attach the guard to the sides with nails.

This birdhouse is ready for the birds!
This birdhouse is ready for the birds! | Source

Birdhouses in Your Yard

Do you put up birdhouses for the birds in your yard?

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More Examples of Condo Birdhouses

Three Unit Condo Birdhouse
Three Unit Condo Birdhouse | Source
Weathered & aged multi-family birdhouse condo
Weathered & aged multi-family birdhouse condo | Source

Trav's Double Decker Birdhouse

Texas License Plate
Texas License Plate | Source

© 2017 Anthony Altorenna


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    • Mary Camley profile image

      Mary Camley 

      2 years ago

      Beautiful design, the licence plates are a nice touch too!


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