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Dirt Crawlspace - typical smell

Posted by geesh (My Page) on
Sat, Nov 19, 11 at 8:52

I currently have 9 mil black plastic covering about 99% of my dirt crawlspace and open vents in a humid climate. The dirt underneith the plastic now smells terrible. I have tried to get someone from the "encapsulation" business to come out & give me an estimate as I dont have any idea what that cost runs. Since apparently they dont need the work, I am considering doing this myself. Question is can I get the same result if I cover the crawlspace walls with a similar plastic and seal the plastic on top the existing plastic on the floor & seal the plastic twds the top of the block walls (leaving a few inches on top uncovered for inspections)& sealing the supports & pipes. Completely sealing the vents and access door and then adding a dehumidifier running the drain hose out of the crawlspace. (Sealing with some type of construction adheasive in a caulk gun).

My concern is reading some posts on another forum is- some people did not notice much smell improvements.

What opinions do yall have here.. Thanks..


Follow-Up Postings:

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RE: Dirt Crawlspace - typical smell

Is the plastic sealed to the stem walls?

Have you tried forced ventilation?


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RE: Dirt Crawlspace - typical smell

no, the plastic is not sealed to anything, just laid on top of dirt & it is now wet & stinky under the plastic. I did leave a fan running down there for about 4 weeks just to move air around. but there was no difference. The mildew smell from under that plastic is very overpowering.


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RE: Dirt Crawlspace - typical smell

I have essentially the same problem-6 month old new construction with crawl. Dirt (southern clay!) covered with black plastic, but plastic not run up walls. VERY wet under plastic, also very humid in crawl. Not sure how to dry the dirt under the plastic....


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RE: Dirt Crawlspace - typical smell

jeannc , Congratulations on the new home. So what are YOU considering to resolve your issue ?

Just so you know, I considered removing the plastic & killing the mildew underneith & starting over... BUT I remembered that when we first looked at the house it was wintertime & it didnt smell.. When we looked again in the spring the smell appeared...and THAT was before the plastic went down, so I do not think the plastic caused the problem..

I am thinking about getting a roll and covering the walls and overlapping the plastic on the floor, and sealing along the top of the wall, and sealing where the plastic overlaps and sealing along any pipes & supports. That has got to help.
All that said, My area does have natural springs that pop up where ever they want.. So I would probably be wise to install a sump pump in the lowest part of the crawlspace.
Very interested in your attempts & results... Bill


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RE: Dirt Crawlspace - typical smell

I am not sure what to do! Probably extend the plastic up the walls somewhat. Right now, the humidity in the crawl is 69% (the outdoor temp is about 50). It has not dried out at all since the heat/humidity of summer. Mildew is growing on the floor joists.

We should be having colder weather soon-I am certain the humidity will drop then-I have not closed the vents yet, either. Seems like the longer they are open, the better.

I would love to do encapsulation, but do not have the money (the crawl is around 2200 square feet).


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RE: Dirt Crawlspace - typical smell

Looks like we are in the same boat. Lucky for me, the house I am working on is a vacation home- so I dont have to deal with the smell everyday. Next time I go down ( late January) I plan on using an adhesive to glue as much of the floor plastic to the walls. Then I can assess how much more plastic I will need. ALSO, the smell "in theory" should be better. I should also check my humidity.. As far as the mildew on your joists, they make a mildew killer you can spray on the wood. I dont think you can dry the dirt underneith since the wetness comes up from the earth. So we either SEAL IT, or leave it uncovered & vented with vent fans.. At least that is what I am learning here at GardenWeb. Hang in there, we will get our issues solved. I will report back in January.. Maybe Ill post pictures.. Bill
* My place is on Table Rock Lake 7 miles from Arkansas.


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RE: Dirt Crawlspace - typical smell

Sorry for the delayed follow up post. I never did seal my plastic on top of the dirt floor. But in March, I closed all but one vent. In two of the vents (opposing walls) I installed these dual fans.(Tjernlund UnderAire� Crawl Space Ventilator � Deluxe Two-Fan, 220 CFM, Model# V2D). I also put in a humidistat that now reads 64% humidity. After being away from the vacation home for 2 months, the smell inside was still noticeable- but barely. Actually not sure of it was the crawlspace or the wood burning fireplace. Never the less, I am on the right track. *In March I found a remains of a large snake in the crawlspace.. We have Copperheads & Cottonmouths in the area- so Im not thrilled of going buck under. Wish the plastic was white so I could see a snake as I crawl around. I am thinking of closing the remaining vent. Does that sound like it would help ? Is the one vent open letting moist get sucked in from the fans ? Thanks for your inputs.


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RE: Dirt Crawlspace - typical smell

Any open vent is allowing moisture into the crawlspace, but it sounds like that snake was the source of your odor, but the snake was there for a reason. Probably there for mice. That's another reason to just fully seal the crawlspace. If you still got a smell you might check this list to see if it helps you at all: http://mycrawlspace.net/mycrawlspacestinks.aspx

Here is a link that might be useful: My Crawlspace Stinks


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