A futon is a folding bed that doubles as seating when it's not used for sleeping. The mattress is not attached to the frame, making it more portable than traditional sofa beds. Futons come in sofa, love-seat and chair sizes and a wide variety of designs that match most decors. These instructions are for a mattress that is longer than it is wide. Only minor changes are necessary to adapt them to different-shaped futons. Use heavy-duty fabric to extend the life of the futon mattress.
Open the futon frame and measure the length and width. Cut a piece of fabric the size of the length and width plus 4 inches on each side.
Lay the fabric face down on the floor or a large flat surface. Cover the fabric with batting that is the actual length and width of the futon frame, leaving 4 inches uncovered on each edge.
Cut a 4-inch thick piece of foam the length and width of the futon frame.
Score the foam down the centre at the place the mattress will fold when the futon is upright. Measure to find the centre and draw a straight line to use as a guide. Use a razor knife to make a 1-inch cut along the line.
Lay the foam on the one side of the fabric with the cut side down, leave 4 inches along the sides. Pick up the piece of fabric and batting (without the foam) and carefully fold it over so that the edge meets the opposite edge. Line up the shorter sides so you have a rectangular package with foam in the centre, then batting, and then the fabric. Use straight pins to keep things in place.
Start creating seams at one of the short ends. Fold the fabric as though you were wrapping a gift. Fold the corners in on both sides, pull the unfinished ends together, fold one under the other and use straight pins to secure it.
Use a slipstitch to sew the seam. Repeat this process on the other two sides or stitch a long bag-type zipper into the remaining open side so the fabric can be removed for washing.
Use a thicker piece of foam for a thicker mattress. Adjust the seams accordingly. Sew a futon mattress cover to keep the mattress clean. Sew two contrasting pieces of fabric together to make a reversible futon mattress.