Tips for Sleeper Installation - Amazon S.3o Gap decking from solid object (wall) 1/4 in. – 1/2 in. ? Ensure proper construction and fastening of the sleeper system by starting with the highest point of the surface to be covered to create a flat and level surface. Note: Using spacers (plastic pads) under the sleepers every 16 in. (406 mm) will help both drainage and.