[gthomas785]

Hi has anyone dealt with a crawlspace like this? The ground is very uneven, covered with boulders and a lot of support columns. House was built in 1850.

The ground is very damp as you can see. I've put a 70 pint dehumidifier since this photo was taken and it really helps keeping the humidity around 70%. I'd like to add a vapor barrier on the ground to further reduce moisture intrusion. I'd say there's about 18" of clearance to crawl around in there.

Any ideas? Should I just cut out an oversized sheet of poly and lay it on top of these rocks? I guess if I measure carefully I can pre cut the holes for the chimney and support columns, then I'd only have to tape the slits afterwards. Seems like whatever I do is going to be a pain in the butt.

 

[Nealtw]

Tough one, what is the foundation, it looks like wood?

 

[gthomas785]

There's a stone foundation around the perimeter. The wooden support posts are also sitting on large rocks buried in the ground.

 

[3onthetree]

If you are looking for a smooth surface to crawl through, and where the poly might not get caught on a sharp edge of a rock, put some pea gravel down first then the poly.

 

[Nealtw]

Are the rocks just in one area or are they everywhere down there, how is it for crawling around?

 

[gthomas785]

Are the rocks just in one area or are they everywhere down there, how is it for crawling around?

They are pretty much everywhere. The flat section (where I took the photo from, and where the access is) already has a plastic sheet with 3/4 crushed stone over it. I think the PO started this project and gave up when they got to the rocks. The rocky area is about 16' x 20' and has a chimney right in the middle.

Beyond that 20' is a stone wall holding up a big beam that runs across under the middle of my dining room floor. The crawlspace beyond that is even less accessible - only access is a 3' wide gap in the foundation and by my estimate about 8" of clearance. No way to get in there but I can poke things around with a long stick.

 

[gthomas785]

Oh, and there's a kitchen bumpout. Think I could get in there?

 

[Nealtw]

They are pretty much everywhere. The flat section (where I took the photo from, and where the access is) already has a plastic sheet with 3/4 crushed stone over it. I think the PO started this project and gave up when they got to the rocks. The rocky area is about 16' x 20' and has a chimney right in the middle.

Beyond that 20' is a stone wall holding up a big beam that runs across under the middle of my dining room floor. The crawlspace beyond that is even less accessible - only access is a 3' wide gap in the foundation and by my estimate about 8" of clearance. No way to get in there but I can poke things around with a long stick.

I guess in 1850 you dig out the dirt and just leave the rocks.
I don't see much success if you can't get every where to seal it

 

[gthomas785]

I guess in 1850 you dig out the dirt and just leave the rocks.
I don't see much success if you can't get every where to seal it

Maybe I'll just run the dehumidifier, at least it's pretty efficient

 

[Nealtw]

Maybe I'll just run the dehumidifier, at least it's pretty efficient

You might be better off with a drain around the outside to cut off the source.

 

[gthomas785]

You might be better off with a drain around the outside to cut off the source.

Now there's a project! Probably not happening this year, but I'm sure it would help. We are in a very flat and poorly drained area so the only place to drain it to would be the sump in my basement. As it is now, the sump pump just pumps back out into the flat yard anyway so I could probably improve that situation as well.

 

[Bud9051]

If you cover 50% of an area you (theoretically) reduce the moisture moving into the air by 50%. It would be a tough dig to find that info so not at this time.

Also using a heavier material, I'm thinking a canvas, you could more easily push it to where you want it and it would stay all by itself.

I see no way you will be able to create the ideal vapor barrier over that dirt and boulders and up the walls, but I do believe you can reduce the humidity with a good effort.

Good luck and glad that isn't my crawlspace.
Bud