How to Build a Window Seat

Guide a circular saw with a straightedge jig to crosscut two 16-inch-wide pieces and one 50-inch-wide piece from a sheet of 3/4-inch birch plywood as shown in the cutting diagram. Use the circular saw alone to cut two 20-inch-long pieces (C) from one of the 16-inch-wide pieces.

On each side piece (C), mark one edge at 19 inches and the other at 16-1/4 inches as shown on the cutting diagram. Draw a line between these points. Starting at the 16-1/4-inch mark, cut to these lines with the circular saw guided by the straightedge jig.

To make the lid (A) and hinge rail (B), use a tablesaw or a circular saw with straightedge jig to rip a 21-1/2-inch-wide piece from the 50-inch-long section of plywood. Working counterclockwise, rout a bullnose on one long side and both ends of this piece.

When an edge is completely rounded over, it is called a bullnose. To make a bullnose on a 3/4-inch-thick piece of stock, use a piloted 3/8-inch roundover bit. Rout around the top of the workpiece. Then turn the workpiece over and rout on the other side.

A bullnose is only one of many ways you can finish the edges of the lid and hinge rail. For a square painted edge, just coat the edge with wood filler and sand smooth. For a square edge with a clear finish, use edge-banding tape. Or pick a 3/4-inch or slightly wider molding to glue and nail to the edges. Reduce the dimensions of the lid and hinge rail to fit the thickness of the molding.

Set the tablesaw fence at 19-3/8 inches. Rip the hinge rail from the lid by running the 21-3/8-inch-wide piece through the saw with the long bullnose against the fence. Make sure the remaining piece is 2 inches wide for the hinge rail.

Rip 16 inches from the remaining 50-inch-long piece. Crosscut this piece to 48 inches to make the back (E). Rip-cut three 3-1/2-inch-wide pieces from the remaining piece, then crosscut these into three 20-inch pieces and three 18-inch pieces for the supports (F, G).

Lay out the cuts for the upper and lower supports as shown in the diagram below. Clamp the stock down and make the angled cuts with a circular saw. Then cut the notches in the upper supports with a jigsaw or handsaw.

Routing a bullnose on plywood works fine if you intend to paint the lid because you'll fill voids and hide the plywood layers with wood putty.

If you want to give your bench a clear finish, start with a piece of plywood 20-5/8x48-1/2 inches for the lid and hinge rail. Glue and clamp a 3/4x3/4-inch hardwood to both ends and one long side of the piece, using miter joints at the front corners. You can use 4d finishing nails instead of clamps, but be sure to center them top to bottom and set them deeply. Rout the bullnose, then rip the hinge rail from the lid.