How to Make a Bench in a Bay Window

Measure the back wall and two side walls of your bay window, as well as the distance across the front of the bay window, where the front of the bench will be.

Cut a piece of 2-by-2 lumber to 4 inches shorter than the back wall, and cut two pieces of 2-by-2 lumber to 4 inches shorter than the side walls. Cut one piece of 2-by-2 lumber to the front length of the bay window. These are cleats for the bench.

Decide on the height you want the bench to be, and place the back wall cleat centered on the back wall at this height, using a level to ensure the cleat is straight.

Tap the wall with a screw or something hard to listen for the sound change where the wall studs are placed. Secure the cleat to the wall with two 3-inch drywall screws through the stud positions in the wall. If you can’t find the studs by tapping the wall, use a stud finder.

Attach the two side wall cleats at the same height, but position the end closest the front of the bay window, 2 3/4-inches back from the front. This allows the front cleat to attach to the ends of the side cleats, with room for the plywood front of the bench as well.

Fit the front cleat across the front of the bay window, with the ends against the side wall cleats. Secure the front cleat to the ends of the side cleats with two 3-inch screws through each end. The front cleat may look a bit saggy at present, but will be reinforced with the plywood front.

Cut two piece of 2-by-2 lumber that go between the back wall cleat and the front cleat. Fit them about an inch from the end of the back wall cleat across the bench, so that one end is flush with the top of the back wall cleat, the other flush with the top of the front cleat.

Secure in place with an angle bracket on each side of the cross supports between the front cleat and the back wall cleat, using 1 1/2-inch screws through the angle bracket screw holes.

Cut a piece of 3/4-inch plywood to the height of the front cleat, by the length of the front cleat. For example, if the bench is to be 15 inches high, and the cleat at the front is 60 inches, then cut a 15-by-60-inch piece of plywood.

Fit the plywood across the front of the front cleat, with the bottom of the plywood flush with the floor, and the top of the plywood flush with the top of the cleat. Secure the plywood to the cleat with 1 1/2-inch screws every 5 to 6 inches through the plywood into the cleat.

Fit three angle brackets between the plywood and the floor, evenly spaced along the length of the plywood. Secure the brackets with 1/2-inch screws through the bracket screw holes into the plywood, and 1 1/2-inch screws through the bracket screw holes into the floor. This will help hold the plywood in position.

Cut a piece of plywood into a trapezoid that mirrors the shape of the bay window. It should have one side the length of the back wall, which will be parallel to a side the length of the front of the bay window, with the two remaining sides the length of the two side walls.

Sit the trapezoid piece of plywood over the top of all the cleats. It should be flush with the back and side walls, and flush with the plywood at the front of the front cleat. Secure the bench top in place with 1 1/2-inch screws driven every 5 to 6 inches around the edge of the top into all the cleats.

Caulk any gaps between the bench top and the walls, and the front plywood and the wall or floor. Smooth the caulk over with a damp finger and let dry before painting the bench.