How to Fill Window Gaps in New Construction

Install a full stud that is the height of the wall at each outside edge of the rough opening; this is generally about 6 inches wider than the finished window. Nail these studs in place with 16d framing nails driven with a hammer through the top and bottom plates. Use a tape measure and framing square to make sure these studs are square with the outside plates.

Build a window header with 2-by-6 inch boards for a standard wall and a 1/2-inch plywood spacer between them to make the header the thickness of a stud. Cut both boards and plywood with a circular saw to the width of the frame between the full studs. Mark the specified height on each stud and set the header in place. Use a 2-foot level to check for plumb and fasten the header with framing nails through the studs and into the header.

Cut a 2-by-4 for a horizontal footer or sill at the bottom of the rough frame opening. Level it and nail it in place through the side studs. Measure the depth of the opening between the bottom of the header and the top of the sill and cut studs to fit as supports between them. Nail the supporting studs on each side of the frame to the full studs.

Measure from the top of the header to the bottom of the top wall plate and cut short studs to fill that gap. Put one stud above each inside stud in the frame and others at 16-inch intervals in between. Fasten these with nails through the top plate into the studs and toe-nail them diagonally through the stud bottom into the header board.

Cut similar studs to go between the bottom of the sill and the top of the bottom plate. Put two below the outside edges of the rough frame and others spaced 16 inches apart in between. Nail these through the top of the sill and the bottom plate into the stud ends.