How to Frame Angled Bay Walls in a House

Measure the width of the subfloor on top of which the face wall will be installed. Mark three 2-by-4s to this measurement and cut them on a chop saw or miter saw. These boards act as a sole plate and a doubled top plate. Cut a window-sill plate 3 inches shorter than the sole and top plates. Cut two full-length studs the height of the floor to ceiling, less 3 inches.

Face-nail the two top plates together with 10d nails. Lay the doubled top plates on the subfloor, and lay the sole plate about 8 feet away. Lay one stud between each end of the plates to create a rectangle. Mark with a carpenter’s pencil the location of the window-sill plate on the studs, based on your plans or blueprint. Lay the window-sill plate in place. Hammer two 16d nails into each joint: between the header and sole plates and the studs, and the window-sill plate and the studs.

Measure between the window-sill plate and the sole plate. Cut short studs to fit this span, enough so that you create one every 16 inches. Mark the short stud locations on the window-sill plate and sole plate. Nail the studs in place. Nail a header, typically a doubled 2-by-10 with a ½-inch panel of plywood adding as a spacer, between the studs just under the top plates. Cut pieces of 2-by-4 -- called "jack studs" -- to fit between the header and the window-sill plate and the window-sill plate and the sole plate -- and nail them into place.

Lift the framed wall into place with the help of an assistant. Line up the outer edge of the wall framing with the top of the band joist at the ends of the cantilevered floor joists. Have your assistant hold the wall in place. Nail the sill plate to the subfloor between each stud bay. Support the wall with a temporary 2-by-4 brace tacked with nails between the face wall’s top plate and the top plate of the main wall.

Cut sole and top plates for each of the projection walls, angling their ends to snugly meet those of the existing sole and top plates of the face wall and main wall. Cut window-sill plates, full studs and short studs as you did for the face wall, and similarly nail them together. Add a header and jack studs as for the face wall. Lift each projection wall into place with your assistant. Nail the projection wall framing to the subfloor -- and temporarily support it with a 2-by-4 tacked to the main wall’s top plate.

Cut scrap pieces of 2-by-4 on a miter saw at angles to fit as blocks between the outer edges of the studs, one at the height of the window-sill plate and one halfway between the window-sill plate and the top plate. Nail these into place, through the studs and into the block.