There is a crawl space under my uncovered front porch. The walls seems to be a mixture of cinder block and brick. The crawlspace "ceiling" is a cement slab and the floor is dirt. The floor right now is covered with various bits of rotting wood. The floor is level with the sorrounding ground. There is one small vent in the wall and a rotting piece of plywood as a door. The space stays pretty dry and we would like to use it for storage of things like bikes, yard tools, and maybe even window AC units.

I am in Washington DC so we get below freezing tempratures, but I was still hoping to just do a pour over the roughly graded dirt to keep things cleaner and make moving things easier. Is this feasible? Given this is truly "outdoor" space without any house above it, would I need a liner?

  • If you think it is dry why not make the space usable many small sheds are not much different. Put some ledger boards so you can level the concrete. I have seen small areas done totally by hand with a wheelbarrow to mix sackcreet and a block of wood used as a float to smooth out the job. May not look totally professional but it worked from what I saw.
    – Ed Beal
    Commented Apr 10, 2017 at 16:29

1 Answer 1


The generic term for non-structural pours like that is rat slab, regardless of whether it's for rodent control or not. There doesn't seem to be any logical call for a liner, but local codes and ordinances aren't always logical. There are a few caveats besides that to keep in mind.

  • You'll want a slab at least two inches thick, three would be better. Don't be the guy that makes due with one inch and has it fail three weeks later.
  • I'd pitch the slab away from the house; no need intentionally create drainage nightmares.
  • The point where you want to have the concrete trucked in approaches a whole lot quicker in a crawlspace because lugging buckets on hands and knees sucks. A lot.

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