How to Build Angled Window Seats

Cut 2-by-4 lengths of wood to serve as the three ledger boards that you will install along the walls of the bay under the windowsills. You will need three ledger boards because the outermost windows in the bay are set at an angle. The ledger boards will equal the length of each wall under each sill.

While you will install the ledger boards flat against the wall, you will need to miter
the ends of the center board to the inner ends of the outermost ledger boards. The angle to miter the ends depends on the angles of the bay area. You will also need to miter the outside ends of the outermost ledger boards so they are plumb and flush with the crosspiece you will install later.

Secure the boards to the studs of the bay wall with 16-penny nails, along the midline of each ledger board. If there is a horizontal stud, space the nails by 6 inches. Otherwise, secure the ledger board to each vertical stud with a nail.

Remove the baseboard or base trim along the bay walls.

Create three more ledger boards that have the same dimensions and mitered cuts as the ledger boards you previously created. You will install these ledger boards along the bottom of the wall, where the baseboards or base trim sat. Install these ledger boards in the same manner as you did the three previous ledger boards.

Create top and bottom crosspieces with lengths of 2-by-4 lumber. This lumber will help form the frame for the front of the seat. These pieces of lumber should measure the distance between the outside ends of the outermost ledger boards. To make sure the crosspieces of lumber are plumb and flush with the outer ledger boards, you will need to miter the ends. Secure the crosspieces to the outside ledger boards with nails.

Cut a sheet of pre-painted pine board that is the same length as the crosspieces of lumber. This piece will serve as the front of the window seat. Bear in mind that you will need to cut the side edges at an angle so the wood will seat flush against the walls.

Cut a sheet of pre-painted pine board to create the seat. The board's ends should have the same angles as the walls surrounding the windows so it has a snug fit. The front of the seat should extend over the front board by ½ inch.

Secure the front of the window seat to the crosspieces of lumber using finishing nails spaced 4 inches apart.

Secure the seat to the ledger boards and crosspieces with finishing nails spaced 6 inches apart.

Cover the visible cut edge of the pine board along the front end of the seat with matching iron-on melamine trim, which is also called melamine edging. Cut the trim to size and use an iron to secure it to the edge of the seat, following the manufacturer’s instructions.

Since the pine board is pre-painted, the cuts that you make into it will expose the wood. Adding melamine edging is a simple way to give your window seat a finished look.

Cut ¾-inch quarter-round trim that matches the color of the pine board so it fits along the top of the window seat along the wall. Secure the trim to the wall using finishing nails spaced 6 inches apart.

Cut a length of trim that matches the room’s baseboard so it’s the same length as the front panel of the window seat. Secure the trim to the bottom of the front panel of the seat using finishing nails spaced 6 inches apart.