How to Make Waterproof Cushions

Cutting the Fabric

• 1

  Measure the width and length of your cushions with a tape measure. Divide the thickness of your closed-cell foam in half and add 1 inch to that number--so if it’s 4 inches thick, you'll work with 3 inches. Add this number to each edge of your cushion cover’s bottom and top pieces to add enough fabric to cover the sides of the foam.

• 2

  Fold the waterproof marine fabric in half and cut the top and bottom pieces of the cushions with scissors, and set them aside.

• 3

  Mark the width and length of the cushions onto the waterproof foam, using a tape measure, straight edge and permanent marker.

• 4

  Cut the foam for the cushions on the lines, using an electric carving knife.

Sew Your Waterproof Cushions

• 5

  Place the right sides of the fabric pieces together for each cushion cover, and pin the edges together with straight pins.

• 6

  Sew a 1-inch stitch around the edges started 3 inches on one side, turning at the corner, sewing the next three sides and then turning at the fourth corner and stopping about 3 inches into the same side you started with. Use the sewing machine and thread.

• 7

  Box the corners of your cushion covers by pulling the two layers apart at the corners to make a triangle with the seam in the middle. Stitch across using the measurement of your foam’s thickness, using the sewing machine--if using 4-inch-thick foam, come in from the point of the triangle to where a stitch across it will measure 4 inches. Stitch each corner the same way.

• 8

  Fold in or cut off the excess fabric at each corner between the boxed corner stitches and the corner’s tip to prevent the fabric from bunching at the corners. Use the scissors to make any cuts.

• 9

  Turn the waterproof cushion covers inside-out and stuff the foam inside each cover. Fold in the raw edges of the fabric at the opening, pin it closed with a straight pin and stitch across with the sewing machine.

Waterproofing Existing Cushions

• 10

  Wash your existing cushions and let them dry. This is a money-saving option for cushions that are still in good condition.

• 11

  Spray a coating of fabric waterproof spray over the entire cushion according to the manufacturer’s instructions.

• 12

  Set the cushions aside in a well-ventilated area to completely dry before using. Check the manufacturer’s suggestion for when to apply more coats of waterproof spray.