Cottage Q&A: Best shed foundations

An open shed with tools inside By B.Forenius/Shutterstock

We’re planning to put up a shed (12-by-20-feet). We have received various ideas as to what this structure should sit on: concrete blocks; a layer of stone or gravel; dig down six inches, and then fill with gravel. Which one is the best suggestion?—Don Whelan, via email

We asked Cottage Life’s star builder Wayne Lennox, who designed “The Little Shed that Could” in our Oct. ’19 print issue. (You read it, right?) 

“That one is easy,” he says. None of the above. Because the best suggestion is, of course, to get a building permit—since the shed is 240 sq. ft. in size, you’ll need one—and then, based on any restrictions or requirements from your building department, decide from there. Some municipalities might require that you anchor your shed to the ground (with rebar, for example); or the permit could dictate where on your lot you can build, and that could dictate what you have to do to accommodate the conditions of the build site. Is the ground soft? Rocky? Level? Gently sloped?

Even given site specifics and permits, “there are just so many ways you can do this,” says Peter Nietlispach, who owns Peacock Woodcraft in Temagami, Ont. But, in general, “the bigger the building, the more support you’re going to need underneath it.” He would opt to excavate four to six inches, remove the topsoil, and fill with gravel, then put down a rectangle of 24-by-24-inch patio stones. A concrete slab is another, extra-robust option, but it’s more complicated and expensive to install.

You could then simply make the patio stones or concrete slab the floor of the shed, says Sean Harris of the Little Building Company in Peterborough, Ont. If you use a wood floor, on the other hand, it’s best to raise it. “The benefit of raising a shed with a wood floor is that it helps prevent rot, and that can prolong the life of the building,” says Harris. He likes to keep a wood floor up at least six inches; the Cottage Life shed used 4x4s in each corner.

Good luck, happy shed-making, and send us pictures when you’re done.

This article was originally published in the Mar/Apr ’20 issue of Cottage Life.

Got a question for Cottage Life’s Cottage Q&A? Send it to

Featured Video