Installing Dormer Skylights
If you have a large, blank cathedral ceiling in one of your rooms, you might consider installing dormer skylights. The skylights will provide extra light and add visual interest to your ceiling. In addition, the skylights will enhance the appearance of your roof outside. Equipment list: Hammer Nails Drill, with drill bits and driver bits Circular saw Reciprocating saw Miter saw Measuring tape Level Plumb bob Speed square Leather gloves Safety glasses · This project requires advanced carpentry skills. · Safety first! Use toe boards, scaffolding and other fall protection equipment when you work on the roof or other high areas. - Measure the roof to determine where to place the dormer skylights. Compare your measurements to the room underneath to make sure the skylights won't look out of place.
- Remove the shingles and felt paper from the roof in the areas where you'll be installing the skylights (figure A).
- Look for the nail heads that indicate the location of the roof trusses. The dormer skylight will span three trusses, so you'll eventually need to remove the one in the middle. Wait until after the dormer frame is in place to cut the roof.
- Begin building the dormer, starting with the front wall. The bottoms of the studs will need to be cut at an angle that matches the slope of the roof (figure B). To determine the slope of the roof, measure 12 feet up the slope, then determine how high above the starting point the slope has risen. For example, many roofs would rise 9 feet for every 12 feet up the slope, which would mean that the roof had a 9/12 slope.
- Use the numbers on the speed square to determine the angle at which the studs must be cut (figure C). For example, if the roof has a 9/12 slope, you would set the speed square on "9" to mark your angle (figure D).
- Cut the studs with a miter saw.
- Build the window assembly (figure E), which will consist of a header at the top, interior and exterior uprights, and a sill at the bottom. Fit the window assembly inside the front wall (figure F) and nail it into place.
- Nail a 2"X4" board to the bottom of the front wall/window assembly (figure G). Then nail the 2"X4" to the roof using sixteenpenny nails (figure H).
- Attach the top plates, which extend from the roof to the top corners of the front wall (figure I). The top plates should have beveled ends to match the slope of the roof, and they should be long enough to extend past the front wall; you can cut them to size later. Make sure the front wall is plumb and that the top plates are level before nailing them into place.
- Install the bottom plates directly onto the roof (figure J). The bottom plates extend from the end of the top plate to the base of the front wall.
- Using a level, mark the positions for the intermediate studs (figure K). The dormer will not be supporting much weight, so you can place the studs on 24" centers. Cut the studs to size, and nail them in place.
- Use a miter saw to cut the rafters to size. Cut the ends at 45-degree angles so that they are parallel to each other (figure L).
- Use a jigsaw to cut a "bird's mouth," which is a 90-degree cut where the rafter will rest on the top plate (figure M).
- Attach the ridge beam (figure N), which fits between the rafters and attaches to the roof at the center of the dormer. The end of the ridge beam should be cut at an angle so that it will fit properly. Level the ridge beam, and attach it to the roof and the front wall rafters. The front of the ridge beam should extend past the front wall.
- Attach the rafters to the ridge beam and the top plate. The last rafters will be attached to the ridge beam and the roof and will not require a bird's mouth cut. Instead, make a compound miter cut on the ends of the last rafters so that they will fit flush with the roof (figure O).
- After the framing is finished, measure and cut a hole in the roof beneath the framing. Use a reciprocating saw or a circular saw with a demolition blade.
- From the roof, use a plumb bob to determine where the ceiling should be cut from below. Drive nails at the corners to serve as reference points, and cut the ceiling with a reciprocating saw.
- Reinforce the framework around the opening by doubling up the trusses and rafters on either side (figure P). Add extra lumber to the trusses and support them by nailing and gluing plywood strips to the sides.
- After the framework is supported, use a reciprocating saw to cut out the truss in the center of the opening. Use a safety rope to help support the weight of the truss, and pass it down through the ceiling opening.
- "Head out" the opening by installing cross framing between the two side trusses directly beneath the roof opening (figure Q). Check your local building codes to determine the size requirements for the header.
- Install 2"X4" studs for attaching the drywall (figure R). The framing is not structural but will make the opening flush so that the drywall fits properly.
- Use eightpenny nails to install 1/2" strand board sheeting on the outside of the dormer (figure S). Start with the sides and then install the front piece, which should be made from a single piece of sheeting.
- Before sheeting the roof, install 2"X6" subfascia beneath the ends of the rafters (figure T). The subfascia will hold the ends of the rafters together and will serve as a nailing framework for the fascia and soffit trim boards.
- Attach sheeting to the roof. Leave a gap at the top so that you can install a ridge vent, which will provide proper ventilation (figure U).
- Attach two strips of 15-pound roofing felt to each side of the roof sheeting.
- Run a bead of caulk around the window opening, and install the window. Use a window that matches the style used for the rest of the house. If your sill is perfectly level, you won't need to level the window.
- Install step flashing around the bottom side corners and one piece of flashing at the bottom of the front wall.
- Use good quality wood to cover the subfascia (figure V), and install soffits under the overhang.
- Install shingles and siding that match the rest of the house.
- Install drywall around the inside of opening using standard drywall techniques.
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