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How to Build a Shed Floor
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Step by step (Home Depot's 8x12 shed)
- Build the perimeter. Assemble a square box of pressure-treated 2x8s equal to the shed's length and width, nailed with 16d galvanized nails.
- Square it. Measure diagonally corner to corner.
- Set the foundation. Place the frame where the shed will sit, find the high corner with a level and set that concrete deck block first on 5 to 6 inches of compacted crushed stone. Level the other corner blocks to it and add a mid-span block on each 12-foot run. See our foundation guide.
- Add joists. Joists every 16 inches on center, running across the short span (8 feet in this shed). Nail through the band joist into each joist end, then add joist hangers.
- Square again, then lay a sheet of 3/4-inch plywood or tongue-and-groove sheathing in one corner to help square the frame. Nail with 8d ring-shank nails. Optional: add exterior subfloor adhesive on the joists first.
- Finish the deck. Cut the last sheets to fit and stagger the joints.
Floor on skids
Skids make the floor movable and cheap. Fix This Build That used a 4x4 skid system (a 10x12 shed on a 12x14 foundation) with a perimeter of 2x6 pressure-treated joists 16 inches on center, blocking between joists for rigidity and 3/4-inch plywood. It notes a concrete slab would have cost $960 to $1,440 and made the shed hard to move.
Family Handyman's cheap storage shed starts with two trenches 16 inches wide, 12 inches deep and 13 feet long, a 3-inch layer of compacted gravel, then treated 6x6s cut to 12 feet and set parallel with outside edges 6 feet apart, covered with treated 3/4-inch plywood. On sloped ground, raise the low 6x6 with stacked treated lumber.
Common mistakes
- Family Handyman warns that a few concrete blocks alone can cause problems later when the ground freezes and thaws unevenly.
- Untreated wood siding or trim installed too close to the ground will likely rot, so use treated, durable materials near the ground.
What will your shed cost?
Our free calculator compares building it yourself, buying a kit and hiring a builder for your exact size.
Open the shed cost calculatorCommon questions
How far apart should shed floor joists be?
Both Home Depot's 8x12 shed and the Fix This Build That 10x12 shed space floor joists 16 inches on center.
What size lumber for a shed floor frame?
Home Depot builds the perimeter of an 8x12 shed floor from pressure-treated 2x8s; Fix This Build That uses pressure-treated 2x6 joists on a 4x4 skid system. Your span and load decide it, so follow your plans.
What plywood should I use?
Both guides use 3/4-inch plywood. Family Handyman's cheap storage shed uses treated 3/4-inch plywood.
How do I handle a heavy mower?
Home Depot says if something very heavy like a riding mower will be stored, place a concrete foundation block under the center of every floor joist.
Don't design it from scratch
A good set of plans gives you a cut list, a materials list and drawings for every step, which saves money on wasted lumber and time on head-scratching. See our guide to choosing shed plans, free and paid.
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