Ok, I plan to cover the dirt in my crawlspace with plastic, as a
temporary measure to reduce humidity down there. Yes, I realize that
this is not a permanent fix, and yes, I realize that I need to address
the source of the moisture problem.
Here is my question: Do I need to treat the dirt with a chemical spray
first, before laying plastic? If so, what chemical? I am thinking
that if mold/mildew is a potential problem, that something nasty could
happen to the dirt if it is cozy in plastic for the winter. Opinions
The plastic moisture barrior under my 'tin shack' (double wide) has been
directly on the ground for the past 7 years and not even the old weeds are
growing under it.
This covering isn't 100% since it is slit and fitted around the support
piers (cinder blocks) but it is very effective since I'm on a hill side and
sometimes drainage water will flow under the house, under the plastic. I
still have stuff stored under there and it remains dry.. But then I have
plenty of air circulation via the many require vent openings.
Actually, most building codes only allow 75% coverage of the crawl surface. The
wood floor joist require a certain amount of moisture. Too much and they sag,
too little and they will dry up and creek. Covering your crawl completely is a
On 5 Nov 2003 16:05:26 -0800, email@example.com (Todd) wrote:
I'd say it depends on 'how' humid it is down there. If the ground is
just the barest bit moist, and there's no standing water or wet dirt,
you can just lay 6mil plastic in overlapping sections.
If there is anything more than the extra tiny bit of moisture crawl
spaces usually contain, i'd look into mitigating that condition before
laying down plastic (which you should definitly do after any moisture
problems are corrected).
Hope this helps
(Remove mypants to reply by email)
If you use a chemical spray you will be the only one who ever did.
Roll out the plastic and address the moisture source in due time.
The plastic doesn't have to be fitted perfectly. If it gets wet on the
underside, it's doing its job.
Most crawl spaces are dirt. But, the standard is to cover
the dirt with 4-6 mil plastic. And no, it is not a
temporary fix, it is essentially permanent. The plastic
does not deteriorate in the dark. The dirt isn't normally
treated and there is no reason to do so. Mold and/or mildew
under the plastic is of no importance. When you put down
the plastic you overlap the edges about 15 inches, Do Not
Seal. If water should enter the crawl space, it will drain
out through the overlaps.
Opinions aren't worth much, or rather, you are likely to
receive some rather strange ideas. I suggest that you take
a look at current building codes in your city or county.
Not that you have to follow the code, but the codes will
tell you what the standards are.
Whoa Tony. Trapping the moisture underneath the plastic is
exactly the purpose of covering the dirt with plastic. BTW,
it isn't dirt, it is soil. You don't want the moisture
coming into the crawl space from the dirt.
The only recommendation I will make is to rake the soil to remove rocks and
bumps. It will make it better if you have to crawl around to do any work in
I have 6 mil plastic under my house that was put there in 1986 when the
house was built. I do not have a mold or moisture problem.
Last weekend I covered all the soil in the crawlspace with 4 mil black
plastic sheeting from Home Depot. It took about a day, including time
spent removing debris from the space (use a snow sled, works really
great for this purpose). I used 4 mil plastic. 6 mil might be
overkill, unless you put it in the areas where you might crawl more
often. I secured edges with large u-shaped staples from the garden
section at Home Depot.
Results were dramatic and almost instant: reduced humidity in the
crawlspace and in the house, reduced smell from the soil, no
condensation on the windows. Total expense was about $50.
One fellow I did some work for, he has a dirt floor in the crawlspace. He
bought a LOT of the interlocking bright colored things (about two foot
square) that daycares use for padding the floor. Put a bunch of those down.
I did this also to my house about 15 years ago, using the clear plastic so I
could see thru it...... I also made some foundation vents about every 25
or so around the outside wall (pier and beam).
As of now, there is no rot, nor moisture buildup under the house. When
I go underneath to look for termites or plumbing leaks, or just to string
cables from one room to another, I don't get messed up.
Also, I put a string of lights, about 10 of the 100 watt bulbs around the
perimeter so I could plug it in when I go down there. Jusst some
outlets on a 100 ft pieced of ROMEX, tacked up to the joists, with a
cord and plug on one end which stays disconnected till I plug it in.
It is a BIG help. No mess, and I can see stuff well. No moisture , rot,
or fungus since the day it was put down.
I really reccommend this. Also, if you can do it when the house is being
constructed, it will save you a LOT of time........
Andy in Dallas
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