Crawl Space

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Old 03-24-07, 08:28 AM
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Crawl Space

I am going to be starting my project soon on the subfloor replacement.
Since I will have easy access to the dirt below one time only, is there anything I can do to cover it, or lay plastic down, or something so that when I am under the home in the future I don't get wet with clay like dirt and dirty as all can be?

I want to do something permenant so that I can always have easy access.

It is always damp and moist under the house. (There is no mold or leaks or anything like that)
 
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Old 03-24-07, 11:36 AM
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You will want to apply at least 6 mil plastic over the bare earth to prevent or reduce moisture from rotting out your joisting. As a secondary benefit, it will keep your pants clean. There many schools of thought on this following topic, so the opinions are like a belly button, everyone has one. IMO, ventilation is important to keep down moisture in a crawl space. But I live in the south and it is required by the Southern Building Code. Other areas don't require them.
 
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Old 03-24-07, 12:13 PM
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I live in California and the humidity is very low here....compared to Georgia (Went to FT. Benning for military training).

From your experience does mildew form on the side of the plastic that touches the earth?

Would you say to hold the plastic down use some bricks in the corners or?

Also, my house has many, many, vents around the perimeter.

Is is normal or safe to install some vent fans in some of the foundation vents?
 
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Old 03-24-07, 02:03 PM
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Eeew, Ft. Benning is a heat hole. Luckily I live in the mountains where the temperatures and humidity are a little more bearable. Mold is not likely to be a problem if the plastic overlaps and does not allow the moisture to reach the wood. It has to have a medium to live on, and plastic isn't as attractive as wood is. Since you have vents all around the house (note they oppose each other all around) you will get sufficient cross ventilation, and fans wouldn't necessarily help. But with that cross ventilation, you may get a little wind that may suck up the plastic, so bricks in the corners and occasionally on the perimeter won't hurt. Don't drive stakes in it as the stakes are....yep...wood.
Good luck with it.
 
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Old 03-24-07, 02:27 PM
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Thanks Larry!
Does it hurt if the plastic is Clear or White as opposed to black?
I hate the creatures (Black Widows) that live in or around the vent holes and black would just hide spiders.

Thanks again. Your opinion is highly regarded.

Fred
 
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Old 03-25-07, 02:59 AM
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Fred, no the color doesn't matter, since you are stopping moisture, and there is minimal light anyway. I usually use the occluded whitish color stuff. That way, if you have to go down with a flashlight, at least you will have some reflection.
 
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Old 03-25-07, 05:46 AM
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Ventilating crawl spaces is old technology. With vents all you are doing is letting the moist air into a cool crawl witch = condensation. Close vents cover ground and walls with 6 mil poly stop on walls one inch before seal plate.
 
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Old 03-25-07, 10:19 AM
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There ya go! I was waiting on this one. Although I disagree, I respect the presenter.
 
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Old 05-04-07, 10:08 PM
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Black has greater UV stabilization by up to 8x over clear or white depending upon the exact composition. Even though it is under the house and dark, UV penetrats, even to 8 inches of common soil.

6 mil black is good, thicker is better. leave some vents open on opposing sides, if you don't, picture this: small leak and what do you get? a swimming pool the size of your subarea. I just rebuilt a home subarea in an affluent developement, 4 years old and $39,000 rot damage due to moisture locked in subarea, the house had louvered subarea vents and moisture barrier installed, their dog liked sniffing around the vents and pushed them all but closed, add a wet bar supply line leak, older couple with heat up high all the time which gets transmitted to subarea...whally...disaster.

If it is always damp in your subarea and there are no plumbing leaks, you have and exterior grade problem, not only will it increase your homes exposure to fungus, termites and wood beetles, it can cause your piers to sink and your foundation to crack and seperate. Correct it.

If you're replacing the subfloor because of fungus damage, you should get a "termite pest inspection" before you even start anything, I always get one before working on anyones house, serves in two ways, they find alot you or your contractor will not, they are legally responsible for what they miss.

BTW it is best to NOT cover the entire soil with barrier, 80% is enough.

California is a big state, if you always have moisture in the subarea, likely you are in the valley, clay soil holds moisture very well, moisture is a house killer.
 
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Old 05-05-07, 07:56 AM
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I appreciate all of the great information

I just went under the house again last weekend.
There are no leaks from any of the plumbing for sure.
I looked closely at the room addition the contractor did for the previous owner before she passed away and noticed insulation held up by a bent wire between the floor joists. Also, I had a sidewalk poured on the north side of the house and a block wall put around it. I think the moisture was coming from that side of the house because dirt and grass that was there was way below normal as compared to the front of the house, not to mention the sun never hits that spot and the dirt and grass were always really wet year round.
After getting out from under the house I had a dirt smell in the whole house for days. The only portion of the house that did not smell was the room addition that had insulation between the floor joists.

DIY projects can be challenging so I am just soaking in everyones great inputs and will post some pictures and replies when I start it.

The main purpose of replacing the subfloor was because in some rooms the house and walls squeeks or sometimes snap sounds when you walk through them. Also, there was extensive damage from either pets or something on the original oak floor and I just had someone put carpet over it to make it liveable for the time being.

I want to stiffen the floors up with some sister joists and put new subfloor that I can screw to the floor joists.

That project in and of itself is going to be hard so trying to do it from under the house would be too hard. I am 6'5" tall and just getting under the house is already a task since the opening is so small. With everything removed it "should" be a snap to get all the materials and tools in and out pretty easily if the whole floor is removed.

Or any other suggestions?
 
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Old 05-05-07, 09:05 AM
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"BTW it is best to NOT cover the entire soil with barrier, 80% is enough."

How so?
 
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