How to Frame a Raised Shed Floor

Build a frame and use it to place the concrete blocks for the shed foundation. Build the frame to the dimensions of the shed; for an 8-by-10-foot shed, for instance, make two end bands 8 feet long and two side bands 9 feet 9 inches to accommodate the end bands nailed to them. Use a tape measure and circular saw to measure and cut the bands. Square the frame using a framing square on the corners and double-checking with diagonal measurements, adjusting it until corner-to-corner distances are the same.

Place the frame in the shed location, which would ideally be a flat area with good drainage and no tree roots or other impediments. Put a concrete block in each corner, in the center of each wall and in the middle of the shed. Lay a 10-foot 2-by-4 across the frame and adjust the blocks using a level until all the blocks are properly aligned. Place blocks with open edges up, aligned so the outer bands rest securely on them.

Cut 2-by-4s for joists; for an 8-foot shed, cut them 7 feet 9 inches to fit between the long outer bands. Install joists 24 inches apart for the length of the shed; set the outside edge of the two end joists at 23 and 1/4 inches to accommodate the width of the end bands. Nail joists through the side bands with a hammer and 16d framing nails, or use metal hangers and hold joists, which are nailed to side bands and inside the hangers, respectively.

Ensure the floor is level again once all joists are in place and make any needed adjustments. Cover the floor with 5/8-inch or 3/4-inch plywood, depending on how much weight the floor must bear. Place plywood with the top grain running across the joists. Cut panels to fit, but stagger the cuts, so the partial panels are not aligned. Nail the plywood to the bands and joists with 8d galvanized nails, or fasten it with 1 and 1/2-inch galvanized screws using a screw gun.