How to House Finches
To house finches, get sturdy, unpainted wood like cedar or redwood that's at least ¾ inches thick to build a birdhouse. Then, start by cutting back, floor, side, roof, and front pieces from the wood. Remember to cut an entrance hole in the front piece that's 1.5 inches in diameter and 4.5 inches above the floor so the finches can get in and out, but their predator the sparrow can't. Next, assemble the pieces together with screws, hinges, and shutter hooks. Once your birdhouse is complete, put it in an open space, rather than a wooded area where finch predators live.
Choose your wood. Select a sturdy type of wood that won't deteriorate over time. For example, choose cedar, redwood, or exterior plywood. You'll need wood that's at least ⁄ 4 inch (1.9 cm) thick and is rough cut on both sides. This will make it easy for the finches to grip and will keep the house from heating up too much. Avoid using wood that's painted since finches are actually attracted to more natural looking houses. If you need to, you can apply a non-toxic stain on the outside. Cut the right dimensions. If you're comfortable cutting the wood yourself, put on eye protection and use a saw (such as a table saw or jigsaw) to cut the wood into 6 pieces. Or buy them from a lumber store that's willing to cut the pieces to size for a small fee. You'll need pieces in these dimensions so they fit together properly: A 7.5 by 13 in (19 by 33 cm) back panel. A 6 by 6 in (15 by 15 cm) floor. Two 6 by 8 in (15 by 20 cm) pieces that slope down to 7 in (18 cm) sides. A 7.5 by 8.25 in (19.1 by 21.0 cm) roof. A 7.5 by 7 in (19 by 18 cm) front. Only use a saw if you've been trained to use one safely. Always use caution and wear eye protection. Get out the screws and hooks. In addition to the pieces of wood, you'll need screws that are corrosion-resistant since they'll be exposed to rain. You'll also need 2 shutter hooks. Get out your drill or screwdriver. You can find screws, hooks, and basic supplies at any hardware store. Cut the entrance hole. Use a jigsaw to cut a small hole on the front piece of wood. This will be the entrance hole for the finches to get in and out of the house. The hole should be 1.5 inches (3.8 cm) in diameter and it should be 4.5 inches (11 cm) above the floor. If your hole is 2 inches (5.1 cm) or larger, sparrows can get in. Sparrows are predators of finches so it's important that the hole is the right size. You may want to drill the entry hole at an angle or add an extra piece of wood to the front piece of the birdhouse. These predator guards will make it harder for predators to get into the birdhouse. If you don't have a jigsaw, ask your local hardware or lumber store to cut the hole for you. Keep in mind that some stores may charge a small cutting fee. Drill holes for drainage and ventilation. Take a power drill and create 0.25 in (6.4 mm) holes in each corner of the floor piece. You should also drill 0.5 in (13 mm) holes at the top on each side piece. These holes will let water drain out and keep fresh air circulating throughout the birdhouse. Placing the roof at a slope will also encourage drainage. Attach the right side piece to the back panel. Get out the 7.5 by 13 in (19 by 33 cm) back panel piece of wood and 1 of the 6 by 8 in (15 by 20 cm) side pieces that slopes down a little. Set the side piece on the right side of the panel so it will become the right wall of the birdhouse. Drill in a screw at the top and bottom of the side piece so it's secure to the back panel. Remember to wear eye protection and work on a sturdy surface. The side piece should slope down towards the front of the birdhouse to support a sloping roof. Attach the floor to the right side and back panel. Get out the 6 by 6 in (15 by 15 cm) floor piece. Place it near the bottom of the back panel so it fits against the bottom of the right side piece. Drill two screws through the bottom of the right side piece so they go into the floor piece. Secure the left side piece to the back panel and floor. Find the other 6 by 8 in (15 by 20 cm) side piece that slopes down a little and set it against the back panel on the left side. This will make the left wall of the birdhouse. Drill two screws through the bottom of the left side piece so they attach to the floor piece. You'll also need to drill 2 screws through the back of the back panel piece so they secure the left side piece. Drill screws through the front panel. Take out the 7.5 by 7 in (19 by 18 cm) front panel that has the entrance hole cut through it. Place the piece directly on the side pieces where they meet the floor. Ensure that the hole is closer to the top of the birdhouse. Drill a screw into each corner of the front piece so it's held to the sides and floor. Attach the hinges onto the roof piece. Take a couple of small screws and screw two hinges onto the 7.5 by 8.25 in (19.1 by 21.0 cm) roof piece. Ensure that the hinges are at the edge of the piece so you can screw the other side of the hinges to the back panel. Secure the roof and hinges to the back panel piece. Set the roof piece on top of the side pieces. The hinges should meet at the back panel and the roof should slope down to rest on the front piece of the birdhouse. Screw the hinges onto the back panel. Attach shutter hooks to the roof. To keep the roof from blowing open, screw shutter hooks onto each side of the roof. Attach the catch pieces directly below the shutter hooks on the side pieces. Test to make sure the shutter hook can reach the catch to close up the roof before you screw it all in. Choose a safe location. Ensure that the birdhouse will be away from finch predators which like to live in thickly wooded areas. Instead, try to put the birdhouse in an open space such as a field, meadow, or backyard. It's fine if the grass is overgrown, since it can give cover to the finches if they need to escape from a predator. Select the height and material of the pole. Once you've decided where to house the finches, you need to secure the birdhouse to a galvanized metal pole. Use a hammer to drive the pole into the ground and then drill holes into the pole. The pole should be tall enough that the house will sit at least 8 feet (2.4 m) off of the ground. While you could attach it to tree trunks or limbs, finches are more likely to be attacked when they're close to the trees. Secure the birdhouse to the pole. To mount the back of the birdhouse to the pole, use a power drill to make a ⁄ 16 inch (7.9 mm) hole through the back of the birdhouse into the pole. Screw in a 1/4-20 by 2 ½ in (M6x 1 x 6 cm) machine screw and tighten it with washers and a nut. Screw in an electrical metal tubing (EMT) bracket around the pole near the bottom of the birdhouse. If you'd like to mount the bottom of the birdhouse onto the top of the pole instead, you can attach it with an EMT screw set connector or a pipe flange. Plant flowers with small seeds around the birdhouse. To encourage the finches to use the birdhouse, grow plants that have small seeds they like around the birdhouse. For example, finches like aster, sunflower, and thistles seeds. They also enjoy dandelion seeds, so you can leave those in your yard to attract the birds. Avoid putting a bird feeder with the seeds right next to the house since this could attract predators. While you can scatter small seeds for the finches, the seeds may attract larger predators. 
Choose your wood. Cut the right dimensions. Get out the screws and hooks. Cut the entrance hole. Drill holes for drainage and ventilation. Attach the right side piece to the back panel. Attach the floor to the right side and back panel. Secure the left side piece to the back panel and floor. Drill screws through the front panel. Attach the hinges onto the roof piece. Secure the roof and hinges to the back panel piece. Attach shutter hooks to the roof. Choose a safe location. Select the height and material of the pole. Secure the birdhouse to the pole. Plant flowers with small seeds around the birdhouse. 