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How to Build a Shed Floor

How to Build a Shed Floor

Constructing a subfloor for your shed provides a solid foundation for years to come. If you're building on a concrete slab, a subfloor is optional: The concrete is its own subfloor. If you choose to build a subfloor over a concrete pad, anchor it to the slab with angle irons, lag screws, and anchor shields. Build a subfloor made of 3/4-inch exterior grade plywood on a frame of pressure treated 2x6s. Strengthen the corners with corner brackets and anchor them to the foundation.

Skill Level: Intermediate
  1. Step 1 Cut the Joists

    Cut the Joists

    Cut the 2x6s to make the four sides of the platform. They're called end and header joists. The headers are the ones that all the other joists nail into. Cut the end joists 3 inches shorter than the frame dimension to account for the thickness of header joists.

  2. Step 2 Build and Square the Frame

    Build and Square the Frame

    Nail the end and header joists together with 10d (3 inch) common nails. Set the frame in place on the foundation. Check for square by measuring across opposite corners. Adjust the frame as needed until the two diagonal distances are equal.

  3. Step 3 Attach Metal Hangers

    Attach Metal Hangers

    Nail a corner bracket at each corner of the frame to reinforce the joint. Attach the frame to the skids with hurricane/seismic ties. Recheck the corner for square.

  4. Step 4 Lay Out the Joists

    Lay Out the Joists
    Lay Out the Joists

    Mark joist positions every 16 inches on the opposing header joists. Extend the lines down the inside face of the header joists with a combination square. Centre a joist hanger at each mark. Drive nails through the flange on only one side of each hanger so you can insert the joists easily.

  5. Step 5 Cut the Joists

    Cut the Joists

    Cut the 2x6 joists to length and set them in the hangers. Press each hanger closed, nail the other flange to the header joist, then nail the hanger to the sides of the joist.

  6. Step 6 Lay the Subfloor

    Lay the Subfloor
    Lay the Subfloor

    Lay 3/4-inch exterior-grade plywood on the joists. Trim panel so joints are at the centre of joists, but stagger the joints so no joint runs into another joint. Leave a gap of 1/2-inch between edges to keep the panels from buckling. Fasten the panels to the joists with 8d (2 1/2-inch) nails or #8-2 1/2-inch deck screws. Space the fasteners every 6 inches along the edges of the panel and 12 inches else where.

What You Need for This Project

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