timber frame foundation

A timber-frame foundation is a wooden rectangular frame that sits on a gravel bed. This foundation is easy to build, easy to level, and ideal for small- to medium-size sheds. And the shed floor can be made of many different materials, including gravel, brick, concrete or pressure-treated, or composite decking.

Step 1: Clear the Area

planning shed location

After choosing your shed site, clear the area of any rocks, trees, shrubs, and debris. Also, check for low-hanging overhead branches so wires.

Step 2: Level the Ground

leveling the ground for foundation

Timber-frame foundations are the easiest to build on a level site. If necessary, excavate and level the area or plan to stack timbers on the low end to build it up and level with the high end. Remove about 4 inches of turf and soil from the area, cover the bare ground with landscape fabric, then spread gravel over the entire site. Compact the gravel with a hand tamper.

Step 3: Get the Lumber Ready

lumber preparation for timber frame foundation

Cut the timber frame from pressure-treated 4x4s, 4x6s, 6x6s, or 8x8s, depending on the size of the shed. And cut overlapping half-lap joints into the ends of the timbers to create interlocking corner joints. Cut the notches with a circular saw, then trim them smooth with a hammer and chisel.

Step 4: Fasten the Frame Together

timber frame assembly

Lay out the timbers and measure the two opposing diagonals, from corner to corner, to ensure the foundation frame is square. Then fasten the timbers together with long self-tapping and structural screws. Drive in the screws with a cordless impact driver.

Step 5: Add Gravel

filling the timber frame with gravel

Once the timbers are screwed together, Overfill the foundation frame with gravel. Then, screed off the excess gravel with a long, straight board.

Now that you know how to build a timber-frame foundation, click here to check out how to frame the floor.


Joseph TruiniJoseph Truini is a host on the Today’s Homeowner TV show and co-hosts the weekly Today’s Homeowner Radio Show. He has written three best-selling shed-building books and lives in Roxbury, Connecticut.

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