Home Forums Hunting & Shooting Hunter's Campfire Help with a Hunting Cabin Crawl Space

I'm currently building a stick-built hunting cabin here in Michigan. It's all roughed in, on a cement block crawl space, with Visquene down on the clay floor and with 4 inches of pea-stone on top of that. I have a drainage tile around both the inside and outside perimeter. When we roughed it in about 1 month ago, I noticed some of the I-joists I received from Carter's Lumber had some black on them and two of them had some white fungus/mold on them. The wood seemed ok, and I had limited time with the crew I had to put this up, so I used them. Some water got in the crawl-space during the build, before it was shingled, and I have it tiled-out, but the clay wasn't really sloped well to have the water run off; some of it just lays tight under the pea-stone on the Visquene. The pea-stone is dry on top, but when I dig down to the Visquene, it's wet. I've gotten out all the water I could, and ran some fans. I don't believe I'll get more water in there now, but not sure if I'll ever get it completely dried out (once I get power hooked up maybe I can run a de-humidifier under there). About half of the I-joists from Carters had mold or something growing on them (half of each I-joist must have sat in the weather at the lumber yard I guess) - so about 1/4 of the I-joists in total currently seem to have a problem (all in the southeast corner of the structure for now). We bleached them a ton this weekend, and hopefully that will help kill it.

Any thoughts on encapsulating the crawl-space? I have 4 vents in there, but honestly, I don't think those alone really promote much airflow. From some of the things I've been reading, it seems some people suggest a heavy-mil encapsulation is better, covering the vents as well to form a complete vapor barrier to control the humidity level, etc.

Also wondering if there are any good products to treat the wood to kill mold and to prevent future growth?

I'd sure appreciate any experiences you've had or suggestions you could make - brand-new place with some problems already, so it's a bummer, but hopefully I can get it treated right and prevent more growth down the road.

Thanks in advance for your help!

DB

The vapor barrier on the floor should be sufficient. If you have a high water table, did you mastic the outside of your block foundation?

The outside of the blocks have a tar-like substance on them all the way up to the grade line - I didn't lay the blocks. This is a solid clay area I've built on, but I'm on top of a sharp hill, so surface water will generally run away from the cabin real good.

Really wondering if that water on the Visquene will evaporate in time? Alternatively, wondering if I should just poke some holes in it when I find a low spot that is collecting some water? Seems it would seep down through the clay eventually. I can't picture water coming up through the clay, but it does seem that moisture comes from the earth and even through the blocks in crawls, so I'm wondering if maybe and entire additional layer on top now and up on the walls might be a good idea? I did put some R5 foam insulation on the block walls right from the start.

Things seem dry under there now for the most part, but once the mold starts I'm not sure how well it can be stopped if the air is humid?

The tar will last for a few years depending on the moisture in the soil. I wouldn't poke any holes in your vapor barrier. Study's show a house without one will absorb upwards of 1800 gallons of water a year.
Vacuume up the water down there now, and when it dry's out your problem will stop.

Okay; I did poke a few holes in a few of my water collection spots, but I'm also pretty sure the seems weren't taped, etc. It's not a perfect barrier, but it covers most everything. On the outside perimiter, I put sand up against the block, so the clay isn't right against it. That hopefully will let water drain down through the sand, through the pea-stone, and into the tile and ultimately away, down over the hill. I like the idea of a shop-vac down there; I'll just keep moving areas of peastone at a time and work my way across the entire floor. Hopefully the bleach will stop the mold.

If you have a problem now it won't get better by itself, take care of it now while it is easier to get to.

The bleach will stop it , but most likely come back close by unless you bleach every inch of the wood and concrete.

I live in a really wet area, and am a Realtor so I hear/read lots of home inspection reports...

VENTILATION is key, with a good vapor barrier.

Your cabin (and the soil around it of course) will be "breathing" moisture for it's entire service life. You just want things to VENTILATE and not just stay wet for months on end.

If I was really worried about it, I'd put in more vents, or put a small fan on the outside of one of the vents, either blowing in or out.

Yeah, I've definately thought about installing a fan down there. Thing is, I read some info. and it seems to suggest the humidity in the basement will just follow the outside level of humidity, best case, with exterior ventilation. I've always heard good ventilation was critical, but these "full-encapsulation" companies claim the humidity level can be kept much lower if everything is covered with the plastic, including the vents! I've really no clue, just know I've got to keep it very dry somehow and kill the mold that came in on the I-joists. I've seen some discussion on Concrobium spray; has anybody had any luck with this? Supposedly it kills mold and retards future growth.