How to Put Windows Into a Gambrel Roof

Build gambrel window frames for roof or wall with top headers, bottom sill plates and side studs between those. Make headers of 2-by-6-inch boards sandwiched around a spacer of 1/2-inch plywood or oriented strand board to fit stud or rafter dimensions. Put two 2-by-4-inch boards together with 4-inch faces up for bottom sills. Use 2-by-4-inch studs for sides.

Nail headers and sills together with 16d framing nails and a hammer. Cut them with a circular saw to the width of the rough window opening, which will be specified with the purchased window. Outline the window frame location on the gambrel end or side. Measure height and width with a tape measure and snap a chalk line to make the outline.

Remove shingles or siding and any sheathing around the window area with a pry bar to expose the studs and rafters. Brace rafters or wall plates with two-by-fours cut to fit between a rafter and roof joist or between a rafter and top wall plate outside the window area. Cut these to length and fasten them with framing nails to support the roof side or wall until the window frame is installed.

Cut rafters or studs at the marked top and bottom locations. Set the header in place first, level it with a level and nail it through the rafters or studs on the sides. Put the sill at the marked bottom, level between the studs. Install doubled 2-by-4-inch partial studs between the bottom of the header and top of the sill, nailed to the studs or rafters on each side.

Measure the height and width of the opening to be certain it conforms to the window dimensions. Measure corner to corner; if those diagonals are identical, the frame is square. Adjust framing if necessary with wooden shims between boards to get the frame square.

Set the window in the rough opening. Run a bead of caulk around the edges and under the installation tabs on the window edges. Secure the window with tapered wooden shims driven at the top and bottom to hold it. Use a level to square and plumb the window, adjusting it as needed with shims around the edges. Fasten it to the rough frame with galvanized screws, driven with a screw gun through holes in the mounting tabs.

Trim the window on the outside with 1-by-4-inch boards or other window molding. Replace shingles or siding removed to make space for the window, after installing metal flashing on all edges of the window. Follow window manufacturer's directions for flashing, which will vary with the type of window.