How to Add a Foam Seat to an Upholstered Chair

Measure the length and width of the seat area, and then determine the depth you want for the cushion. Add 1 inch to each of the measurements and write down the values.

Cut out the top and bottom fabric pieces using the increased length and width measurements. Cut out two side pieces using the increased depth and length measurements, and then two side pieces using the increased depth and width measurements.

Sew the four side pieces together with a one-half-inch seam, matching the right sides together along the short end of the pieces. Alternate a width piece with a length piece so they match the sides when attached to the cushion. Sew the remaining short ends together to make a loop. Press each of the seams open with an iron.

Pin a zipper to the rear edge of the bottom piece of fabric and sew to hold in place. Pin the loop created in Step 3 to the bottom cushion fabric so the right sides match, and sew together with a one-half-inch seam. Pin the loop to the zipper edge, instead of the fabric, along the rear edge of the fabric. You may want to sew the zipper edge first with a zipper presser foot, and then sew the remaining three sides with a standard presser foot.

Open the zipper so you can reach inside the cover after completing the cover.

Pin the top cushion fabric to the top edge of the depth loop, matching the right sides together. Sew all four sides with a one-half-inch seam. Turn the cover so the right side faces out by pulling the fabric through the zipper access.

Cut a piece of upholstery foam to the measurements of the cushion cover. Slide the foam through the zipper access, smooth the cover so it fits correctly and close the zipper.