"Jay Pique" wrote in message
...
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. Do I need a vapor
barrier? Can I just pour right over the dirt? I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP


The ideal would be crushed stone, a vapor barrier, and insulation
under the slab, but I can understand why you'd want to avoid the
effort involved in doing that.

For one thing, a house that old may not have the greatest footers. You
certainly don't want to undermine them excavating for the slab.

If' it's bone dry down there all the time you can probably get away
with putting down a good vapor barrier and pouring on top. But I'd
consult local experts familiar with the area and conditions.

One thing to keep in mind. Wet concrete throws off a *lot* of water
vapor while it is setting and drying out. It has no place to go but
up. In an unfinished house it's not a problem, but you're going to
want to provide positive ventilation to get rid of all the moisture or
you'll be asking for mold issues.

Have you checked for radon? Now would be the time to plan for
remediation if you have a radon problem, and that will almost
certainly required gravel under the slab so the space can be
depressurized and exhausted externally. That's usually the first step
in remediation.

Good luck with your big project!

Paul F.