Diy shed floor advice?

I'm making a 16'X24' shed and I need some advice for the floor joists and beams.

(All lumber will be ground-contact treated southern pine, probably grade 2)

I'm thinking of making 3/4 inch pressure-treated plywood floor on 2X8 joists spaced 16" apart with a 7'9" span, supported by 16' 4X8 beams spaced 8 feet apart, which would in turn be supported by 1 foot wide square concrete pillars set 2 feet in the ground at the ends and middle of the beams for a beam span of 8 feet.

Would this be keep the floor from sagging?

Not enough?


The heaviest single objects will be a large generator, and a large bookshelf full of books, although I may get a riding mower later.

7 Answers

  • Wilson
    Lv 6
    7 years ago
    Best Answer

    I would build up 3, 24' beams using double 2x8's. 1 on each 24' side and one parallel down the center. You could have 2 rows of 2x6 joists between them. 8' spaced piers is a bit too much unless you let your wall sheathing drop down and cover the perimeter beams to help hold them up. For a shed you don't want 8' walls anyway. It'd look way better to incorporate the floor thickness into the 8' sheathing height anyway. You'd have 84" ish studs instead of 93's. Believe me, this will look less Snuffy Smithish. If I were building that shed I might even consider setting 6x6 posts @ 6' centers for the foundation and notching them to support and and windhold the floor system instead of laying it atop of masonry pillars.

  • 4 years ago


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  • Kokita
    Lv 4
    4 years ago

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  • 7 years ago

    it should be enough to support your weight the books will probably weigh more than anything if the book shelf has any size to it and your floor shouldn't sag most homes are 4 foot between piers so for a shed 8 would be fine as it has not even close to the weight a home has

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  • 4 years ago

    Building Amazing Outdoor Sheds -

  • Red
    Lv 5
    7 years ago

    Slightly overkill

    Single 2x8 x 16' beams and 24" centers would suffice..

  • Robert
    Lv 5
    7 years ago

    You'll be fine. Only concern would be the footings. Depending on where you live, 2 feet may not be deep enough. Consider frost heave.

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