Well, I know of a person who is building a house on a crawl space. House is located in Northern WI. The house is almost complete.
Unfortunitly, the entire crawlspace, floor joists and all, are full of mold. It could possibly move to the walls.
Here’s my question. How do you properly prepare a crawlspace for moisture problems?? I was thinking drain tile, both inside and outside on footing, vapor barrier over bare ground, and vapor barrier over insulation in floor joists. Also, proper venting around the crawl space as well.
Let me know your opinions.
upnorth8
Replies
upnorth, there are two basic strategies for crawlspaces: vented or sealed.
I think most building codes currently require vents to allow air to circulate and thereby draw the moisture out. But the 'sealed' crawlspace folks claim that you're better off completely sealing the space and treating it like a part of the house. The sealed folks say that warm/humid air drawn into the crawlspace in the summer will cause moisture to condense on the joists and under the floor, thereby supporting mold growth.
On my current project house, I can see firsthand how much moisture is getting airborne. In areas that have vapor barrier, the dirt is moist underneath, but in areas without vapor barrier, the ground is like a hard-cracked, dry riverbed. All the moisture in that soil has migrated into the house.
If you opt for the vented crawlspace, you have a minimum sq inch of vent space required and have to be setup for cross ventilation. You still have a vapor barrier on the floor, but your insulation is now up under the first floor. What you're trying to do is create enough air circulation to draw the moisture out (and hope you don't have condensation issues).
If you opt for the sealed space, you are going to have a battle ahead of you. You need to completely seal the vents, seal the crawl walls and floors. If you're in an area with a high water table and get water in the crawl, then you also need a sump pit/pump to remove that water.
FHB did an article on sealed a while back:
http://www.taunton.com/finehomebuilding/pages/h00107.asp
They were basically creating a continuous vapor barrier from crawlspace walls down. But keep in mind that you don't want the barrier to extend up to the mudsill because you could be giving termites a hidden path into your home. They were also using a combination of vapor materials, not simply the 6mm poly you get at Lowes.
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jt8
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