How to Cut a Roof for Shed Dormers
- 1). Draw a diagram of the shed dormer that you are planning. The top of the hole that you cut in your roof will need to be high enough so that the roof of the shed dormer still has a pitch to it for shedding water. This means that the top of the hole should be higher than the top of the front wall of the shed dormer. Design the width of the dormer so that its side walls are each directly over an existing rafter, to support the weight of the dormer walls and the new roof above them. When you build the dormer, you should double up these side rafters for added strength.
- 2). Strip away the shingles in the area where the shed dormer will be built. If you are planning to re-shingle your roof, it makes the most sense to build the shed dormer at the same time.
- 3). Mark the corners of the hole you will cut for the shed dormer with a pencil. Snap chalk lines between the pencil marks. These are the sides of the hole that you will cut for your shed dormer.
- 4). Cut along the chalk lines with a circular saw and remove the roof sheathing from the hole.
- 5). Install temporary braces from the attic floor to the underside of the rafters just above the hole that you cut. These braces will support the rafters when you perform Step 6.
- 6). Cut through any rafters that are impinging on the hole and set them aside. You may be able to re-use some of the rafters in the shed dormer. Leave the temporary braces in place until you have framed the new dormer, which will make them independently strong again.
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