You pros have really been of help as I work on our “new†1835 farmhouse. I need your help again. The project du jour is the crawlspace under the original building (there is a frame addition with a full basement). The original brick house was built on a brick and stone foundation just into the clay (not deep at all). There was very little space below the floor joists. When the house was plumbed and electrified in the 1930s, a “stoopspaceâ€, or trench you might call it, was dug by hand, sort of like The Great Escape, as you can see in the photo. The foundation was beefed up at that time with steel beams.
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When we moved in two years ago there was a dehumidifier running down there—it was quite noisy and ate a lot of power. There is no vapor barrier, and the soil is a very firm clay. It seemed relatively dry then. Since then the dehumidifier has died, and we had a big freak rainstorm last January here in central Ohio. After the rain I noticed almost an inch of water at the bottom of the trench in spots. The former owner says he never noticed water down there. Now, after a very dry summer and no dehumidifier, the soil at the bottom of the trench is quite damp in spots, and I have noticed some white mold growing on it. There seems to be very little ventilation to the crawlspace, except for the screened access hole from the basement. We have hot water heat.
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This week I bought a low temperature 45 quart dehumidifier which I plan to place back in there—not looking forward to that. The water will run through a pipe into a basin in the full basement. I’m also planning to spray the white mold with a bleach solution. There doesn’t seem to be much moisture in the high spots of the crawlspace—the trench seems to be where the wetness is. I’ve considered installing a plastic vapor barrier, but you can imagine that it would be very difficult or impossible to do except in the trench itself. I’m wondering what you pros might suggest. Would lining the trench with plastic film, then putting down some plywood for crawling, help at all? I wouldn’t know how to anchor the film. I’m also considering a French drain around the uphill side of the house, although there is no moisture there currently (in spring, there might be).
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Any thoughts, comments, advise would be greatly appreciated.
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Thanks as always,
Marc
Replies
The best solution for you all around is to spray closed cell foam on the ceiling in the damp area.
Use a Corbond or similiar product. It must be 2 lb density, closed cell foam in this high moisture environment.
This will form a continuous VB and also insulate the conditioned (i believe) space above it. Any other VB and you are simply fooling yourself. All plastic sheets have or do develope holes.
This might be expensive up front but you will save a ton in heating and do not need a dehumidifier purchase and waste of electricity forever.
Stu
I was thnkling the same for that difficult space. If he has enough money, he could also spray foam on all the exposed soil to act as a VB, but I don't imagine he has that much cash laying around.
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Rule 1 is to keep water out in the first place, so do your work on the french drain first.
And, of course, you've extended your downspouts 10 away from the structure and provided positive drainage around the house?
Around these parts (I'm near Toledo) when the clay soil gets as dry as it has been lately, the soil pulls away from the foundation slightly, and when we get rain, anything that moves towards the foundation runs between the soil and the foundation first (clay is slow at absorbing moisture) and it gets into the crawls and basements more than in normal times.
One way to determine if this has been a previous long term problem is to look at the underside of the sheathing in the attic above that portion of the house - if there is widespread mildew on the roof sheathing, it is probably an ongoing problem.
The foam idea is OK for insulation value, but I'm not real keen on just leaving that water/moisture down there, out of sight - out of mind isn't that good of an idea.
And I'd be a little worried about that foam possibly trapping water from undetected leaks above it - the details would be all important there - and the damage could be significant. (The big problems with EIFS synthetic stucco have been with foam trapping moisture in walls.)
Interesting idea on the foam--I don't know the details of installation, but I have a feeling it would be difficult. You should see the "ceiling" of the crawlspace, ie the underside of the floor. It's a jumble of pipes and wires, and there is no subflooring. I'm going back in today to install the dehumidifier. Send a search party if I you don't hear from me soon.
Marc
Plastic on the floor will work. A fan may be of more help then a dehumidifier.
Your problem is that moisture in the soil evaporates and condenses on the wood.
Adding plastic above the soil forces the moisture to condense on the bottom side of the plastic and go back to the soil.
My kid's crawl space has always been damp. A couple months a go a water leak poured 20,000 gallons of water into the crawl space. The insulation anf joist bottoms were dripping wet when I laid down 4mil plastic. A week later the insulation was a bit damp but not dripping. This is in a crawl space of 2000sqft with only 2 18"x24" openings.
Plastic on the floor will work. A fan may be of more help then a dehumidifier.
Your problem is that moisture in the soil evaporates and condenses on the wood.
Adding plastic above the soil forces the moisture to condense on the bottom side of the plastic and go back to the soil.
My kid's crawl space has always been damp. A couple months a go a water leak poured 20,000 gallons of water into the crawl space. The insulation anf joist bottoms were dripping wet when I laid down 4mil plastic. A week later the insulation was a bit damp but not dripping. This is in a crawl space of 2000sqft with only 2 18"x24" openings.
Marc, I just read an interesting article in some old mag (FHB?, JFC?) where the contractor solves this problem regularly by doing a cursory drainage correction, then laying heavy plastic -caulked at all seams- right up to the top of the footing. He even sealed off All of the side vents to the crawl, so moist air wouldn't be drawn in to replace rising hot air. With an occasional thru vent to the dirt (to allow radon to escape), the system seemed tight, and made sense.
Personal Note: I had an alarming growth of mold in the perrenially wet dirt under my house, and my first thought was to spray bleach. My second thought was, "This sucks!" Then I read that restorers kill mold on books by dragging them out in the sun for15 minutes. I considered banks of UV lighting to kill the mold, or even propping mirrors up to "sweep" the dirt as the sun moved past. Don't know if that would have worked, because I happened upon a big pile of salvaged solar panels -they're 1/4" thick, pvc "mats". I was able to roll each 4x8 sheet and stuff it through my access door, then unroll it under my house and tape all the seams. In an hour or two I had totally changed the climate under there, plus I had a rigid, dry surface for storage and sliding around. My space was flat, though, and more headroom (30"). The only downside, as I see it, was that the moisture content in my wood floors has changed permanently, shrinking the boards slightly -but it's stable.
Saulgood,
Thanks for the ideas. Glad you found a solution to your problem--nice find on the solar mats. Wish I could find something like that around here. I think I will probably use 6 mil plastic film to cover as much as dirt as possible. The idea of laying down some landscape cloth first, as a protective layer, seems good, although it will add to the cost.
Marc