A dormer can change the outward appearance of a house, but it also can be a major improvement for the interior. A dormer window in a bathroom will open that room to additional outside light. A dormer also can be used to extend the space for a bathroom, by changing a section of the roof from a slope to a framed room with walls. Framing for either of two possible styles is similar, but may require the services of an architect because it involves changing the roof structure. It also will require a building permit.
Instructions
Preparation
1. Prepare a bathroom dormer by making a careful plan to locate it on the roof in an area which will fit the home's style. Open the area by removing drywall on the inside of the bathroom, to expose the rafters on both sides. Cover cabinets and plumbing fixtures with tarpaulins. Cut drywall along a stud line with a utility knife and use the knife and a pry bar to pull off the drywall.
2. Identify the specific location for the dormer's roof opening and mark it with 16d framing nails at the corners, driven from inside the house through the roof sheathing with a hammer. Place the nails on the inside edges of the two studs that will form the outer edges of the dormer.
3. Install braces on the outside dormer rafters, with 2-by-4-inch boards nailed to the rafters above the top line for the dormer and to corresponding rafters on the other side of the roof. Remove shingles from the dormer area with a pry bar. Cut out sheathing inside the marked area with a reciprocal saw and cut off rafters inside the dormer area at the marked top and bottom.
4. Frame the rough opening for either type of dormer. Add a second rafter to the existing outside rafters and put a 2-by-6-inch header board, with a center spacer of 1/2-inch oriented strand board (OSB) or plywood, between those rafters at the cut ends of the top rafters. Nail the header to the side rafters and to the ends of the cut rafters. Install a similar header at the bottom of the dormer opening.
Window Dormer
5. Build a small window dormer by making a rough frame for a pre-built window, with a header and a sill. Make the header of 2-by-6-inch boards nailed together around a 1/2-inch spacer strip of plywood or oriented strand board and a sill of two 2-by-4s nailed together with the 4-inch faces up. Cut these to the width for the window.
6. Nail 2-by-4 studs between the bottom of the header and the top of the sill, on either side, to complete the frame. Set this frame in place between the rafters and brace it temporarily with boards nailed to the frame and to the rafters. Plumb it with a level, then secure it with 2-by-4 top plates between the top of the header and the rafters.
7. Cut dormer roof rafters from 2-by-4s to any desired pitch and erect them between the window frame and the point where the side plate connects to the main rafters. Nail the rafters to the wall plates on either side and to a center ridge board. Cut short studs to fit between the wall plates and the rafters on each side. Connect the top dormer rafter to the roof header with sections cut off the top rafters.
8. Install the window in the rough opening. Install siding to match that of the house. Cut boards or panels to fit and nail them to wall studs. Use 1-by-4-inch boards to trim corners and windows. Cut these to fit and nail them in place, around the edges of windows or on the corners where the walls intersect.
9. Cover the dormer roof with oriented strand board decking, nailed to the rafters with 8d galvanized nails. Staple roofing paper to the decking. Nail metal flashing with shingle nails on all roof edges and at all intersections of wall or roof. Install asphalt shingles; fasten these to the decking with four shingle nails in each shingle.
Dormer Addition
10. Make a dormer addition to create more space inside the bathroom in a similar fashion, but use the outside wall as the base for the dormer wall, so there will be floor space added. Brace the dormer roof area with doubled rafters and a top header, but set the bottom header over the top plate on the house wall.
11. Build a front dormer wall, with top and bottom plates, end studs and studs at 16-inch intervals between. Frame a smaller window, with studs above and below the frame to connect the frame with the top and bottom plates of the dormer wall. Set the in place, plumb it and brace it temporarily.
12. Cut top plates for both walls to connect the dormer front to the house rafters. Frame the outside dormer walls with studs cut to fit between the top plate and the side rafters. Make "valley" rafters; these are rafters cut to conform to the pitch selected for the and nailed between the roof header and the rafters on each side as a base for connecting the dormer. Leave space at the top for a ridge board. Use the cut pieces from the top roof rafters to connect the header and the valley rafters.
13. Cut and install rafters on the dormer. Nail them to the wall caps on both sides and to a center ridge board. Brace them with "collar" ties, braces placed horizontally between rafters just under the ridge board to tie the two sides together. Cut the ends to match the pitch of the roof and nail them on the house sides of the rafters.
14. Add wall studs spaced on 16-inch centers on both sides of the dormer, from the bottom of the rafters to the top of the roof joists, to complete the interior wall framing. Install subflooring in the dormer addition if none is in place; existing joists should support this step. Cut OSB panels to the length and width of the floor and fasten them with 8d nails to the joists. Finish the addition with siding, trim and roofing. Staple fiberglass insulation batts between the studs in the dormer, both above and below the rafters. Finish the interior with drywall, nailed to the studs and roof rafter. Seal the joints with drywall tape and joint compound.
Tags: dormer roof, dormer wall, ridge board, area with, boards nailed, both sides