That time my pressure-treated wood shed floor rotted out in 18 months

I built a shed in my backyard in Portland back in March 2022 and used regular pressure-treated plywood for the floor. By October 2023, I stuck a screwdriver through the boards near the back corner because water pooled under the shed after heavy rain. Turns out I needed to put down a vapor barrier and gravel base first. Has anyone else had ground moisture wreck their shed floor faster than expected?

3 comments

3 Comments

josephbailey10d ago

And honestly the gravel base is key even with a vapor barrier. I think a lot of people skip the 4 inches of crushed rock and just throw down plastic sheeting thinking that's enough. That's how you end up with a swamp under your shed.

charles83610d ago

Took me one soggy shed floor to learn that lesson the hard way lol. Gravel lets the water drain out from under there instead of just sitting against the plastic and finding its way through eventually.

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mark_green10d ago

Yeah the gravel thing is key but honestly 4 inches is overkill for a small shed unless you're parking a tractor in there. I've done 2 inches of crushed rock with a proper 6 mil vapor barrier on top and my floors have held up fine for 5+ years now in Seattle. The real trick nobody mentions is making sure your gravel slopes away from the shed foundation, even just a tiny bit. Standing water will find any crack or staple hole in the plastic. A buddy of mine used that fancy dimpled membrane stuff under his floor and swears by it, way better than flat sheeting since it gives the moisture a path to escape.