How to Make a Cornice Board Valance From Foam Insulation

Measure the width of the area to cover. The inside of the cornice must be at least two inches wider than a hanging curtain rod. Record this measurement as “inside width.” Measure the depth of the area to cover as the distance from the wall to the front of hanging drapes, plus two inches. Record this measurement as the “ inside return.” Decide the length of the cornice, which is an arbitrary measurement. Record this as the “outside finished length.”

Cut the front cornice piece width equal to the inside width plus twice the foam thickness. Cut the foam using a utility knife and straight edge. Try to cut with one pass, making a neater cut edge. Mark this edge as "1." Cut the length of this piece equal to the outside finished length, and mark this edge as "2." Cut the two side pieces width equal to the inside return measurement, mark this edge as "3." Cut the length equal to the outside finished length, marking this edge as "2." Cut the top piece width equal to the inside width, marked as "4," and the length equal to the inside return, marked as "3."

Match the outside edges of the side pieces to the outside edge of the front. ( Edges number 2). The side pieces sit behind the front piece. Looking down at these three pieces, you are creating a U shape; the outside pieces sit on the inside of the front piece, the outside edges being flush. Place glue on the front edge of the side piece and glue in place to the front piece. (Edges numbered 2). Glue the returns (edges numbered 3) and front edges of the top piece to the inside of the U, (edges numbered 1 and 4), creating a four- sided box.

Cover the outside of the cornice box with 5.5 ounce or more polyester quilt batting. Cut the corners as necessary to reduce bulk. Wrap the batting to the inside of the box and and glue in place.

Upholster the box with the chosen decor fabric. Use twist pins to attach the fabric to the box.

Hang the box over the window. Attach angle brackets to the wall, and use two sided tape to attach the brackets to the underside of the top of the valance.