How to Form a Dormer Window
A dormer window expands the living space of your attic. You can form a dormer window in your house's design when you do the initial roofing or you can add it to an existing roof. Two types of dormer windows are common. Gable dormers are perpendicular to your roofline. Shed dormers are parallel to your roofline. You can form a dormer window yourself.
- Read blueprints of the dormer window. You have to determine the rough opening for your dormer window.
- Use measuring tape to make measurements for the outside area of your roof that you want to use to form a dormer window. Mark the area you measured with chalk. Use a circular saw to cut between the roof shingles and then remove those shingles.
- Read the blueprint again to determine the dormer window's dimensions. Take some chalk to mark the front dormer wall's location. Grab a builder's level and then place it on the outside of the window line. Mark the rafters with your chalk. Use the circular saw again to cut the rafters off.
- Cut off new rafters that are the same length of your old rafters. Grab a hammer and use 16d nails to nail the rafters that are underneath the roof's sheathing.
- Use the blueprint to measure the double headers length or the boards supporting the top and bottom of your dormer window. Use your circular saw to cut lumber from the headers. Use 16d nails to nail both headers in place. Plumb the corners of the headers by using a builder's level. Nail 2-by-4 lumber around both headers to brace the headers.
- Nail a corner stud into your roof, so you can insert the side call. Use your circular saw to cut an end of a 2-by-4, so it can form the top sidewall and then nail the top sidewall to corner stud. Cut more 2-by-4 lumber to form a bottom plate. The bottom plate will rest against roofline. Use chalk to mark the bottom plate's length every 16 inches. Nail the corner stud with 16d nails through bottom plate on the roofline. Add one more bottom plate on the opposite side of your dormer window.
- Use your blueprint using the roof slope to create a ridge with 2-by-4. The ridge runs down the middle of dormer window to your roofline. Use your blueprint to determine the slope and length of the rafters. Use 16d nails to nail the rafters to its ridge.