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Tony Sade
08-06-2006, 12:18 PM
I have a dirt floor crawl space in my house and want to install a vapor barrier over the dirt floor. I plan on putting down a 6 mil poly barrier, running up the walls about 6-12" and overlapped and sealed at any joints.

Couple a questions.

1. Because the floor above the space was slightly "bouncy", I installed a couple of homemade laminated beams across the joists, supported by adjustable columns on piers I poured myself. I am concerned these piers and columns are going to make it hard to get a tight seal. Should I just make slits in the poly to slide around the columns and tape around the bottom of the columns ? Any other ideas?

2. What should I use as "ballast" over the poly? I've read that gravel can be used, and also not to use anything that conceivably could puncture the plastic, such as gravel. I've also seen sand suggested. I don't spend a lot of time in the space, but I do store things that I need access to and I don't want either to put holes in the barrier, or make it impossible to get around in. Any problem with the moisture bound to be in the sand? Gravel ok?

Any other suggestions?

Thanks,

Frank Fusco
08-06-2006, 4:31 PM
The vapor barriers I have seen are just as you describe. An air tight covering probably isn't necessary. Stones, rocks, whatever can be used for weight. Once down they only move around at full moon so shouldn't be a problem cutting the plastic.

Jim O'Dell
08-06-2006, 7:08 PM
Use pea gravel insted of crushed stone. No sharp edges, and easier on you when you move around on it, especially when on your hands and knees. Jim.

Ben Grunow
08-06-2006, 10:17 PM
I think the point of covering it is to keep it from getting damaged and moved around when you crawl on it or set something on it. Maybe it would be easier to lay some PT 2x4s and 1/2" plywood to make a floor that wont rot and will allow you to store your stuff. Just put a few screws in the plywood so it can be removed for future work and periodic inspection for mold and insects. If not I would use sand or pea gravel.

I would cut the plastic as carfully as you can around the supports and use caulking to seal the poly to the posts if you're worried about it. It's got to be better than nothing. I would not worry that much considering the edge of the poly will be somewhat open all around. Good luck.