How to Make Deck Risers

Start at the top of the staircase and measure the gap between the surface of the tread on the second step to the underside of the front edge of the top step. The gap between stair treads typically is around 7 or 8 inches. If your stair treads are exactly 8 inches apart, no cutting will be required to fit your 2-by-8-inch lumber into the open space, although the length will have to be adjusted. If not, your lumber will have to be cut to fit both the length and width of the opening.

Use your tape measure to record the length of your existing deck staircase treads. Use your tape measure and straightedge to mark your 2-by-8-inch pressure-treated lumber to fit the spaces between your deck staircase treads. Use your circular saw to make the cuts.

Place one riser in the space between each stair tread. Use your power drill to make pilot holes through the risers and into the stringers behind. Use your screw gun and 3-inch decking screws to fasten the risers in place. Two screws for each stringer location should suffice. Because deck treads have overhangs built into their design, the risers should fit neatly beneath the lip without visibly protruding.