Crawl Space Encapsulation

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  #1  
Old 05-20-08, 05:00 PM
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Crawl Space Encapsulation

My crawlspace is damp and mouldy (dirt floor) and I've been doing some reading and I've decided to finish it with plastic. I can't find the 20 mil poly they recommend so I'm using 6 mil which they said will work. I'm going to do the floor and up the block. My questions are:

1) I know I should use mastic to glue the poly to the block walls but I can't find a product that works (in Canada), do you have any recommendations? (acoustical sealant maybe?)

2) The seams will overlap 1-2' how should I join the seams? I'm thinking tuck tape, any other ideas?

Thanks!

Matt
 
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Old 05-20-08, 06:20 PM
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Matt
I don't know why they would spec 20 mil! 6 mil is standard. Spray glue will hold it to the wall and seal the seams.
 
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Old 05-21-08, 03:51 AM
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Because they sell the stuff and it costs a considerable amount more, meaning more profit if they can suck you into buying it. You may have to brush down the block in order to get good adherence of the spray glue, but that is the best method.
 
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Old 05-21-08, 10:09 AM
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yes, first brush down the block, flakes could possibly clog any pump that you're installing to eject the water/moisture trapped by the barrier.

2nd, look into seeing if the place that sold you this barrier sells the Christmas Tree Fasteners. Better to use those then to use spray glue which could add to a VOC irritation.

3rd you could check out basementdepot.com to see about buying some of the joint tape that's designed specially for the poly-barriers.

good luck.
 
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Old 05-23-08, 08:04 AM
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6 mil liners

Yes, as stated by airman 1994 some contractors do use 6mil liners, but independent studies like the ones compiled by Advanced Energy recommend 20mil crawl space liners for a simple reason: it is reinforced and it lasts longer. Six mil polyethylene rips quite easily when someone crawls over it and, when glued or taped to a wall, it can also be easily pulled down.

In other words, thicker liners might cost a bit more, but they will keep your crawlspace dry and neat for a long time. Think of the cost of replacing and/or repairing the thin plastic over and over.

Manufacturers of the 20 mil crawlspace liners usually offer warranties on their products. (some offer as long as 25 years, against rips and tears). You might have had a problem to buy those liners because usually, the companies selling them are also the ones that install them along with several other crawl space solutions. Personally, Id strongly recommend that you get a crawl space encapsulation pro to take a look at your crawlspace and see what can be done. Some contractors charge you nothing for the evaluation.

Anyway, f you are going to use the standard 6mil, I suggest that you protect it somehow, especially around the ground areas that will be frequently accessed for maintenance.

Also, use mechanical fasteners in addition to the adhesive because the glue alone may not hold it properly. Duct mastic with fiberglass mesh tape is usually recommended to seal the seams.
 
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Old 05-23-08, 08:58 AM
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[QUOTE=CyFree;1369433]Yes, as stated by airman 1994 some contractors do use 6mil liners, but independent studies like the ones compiled by Advanced Energy recommend 20mil crawl space liners for a simple reason: it is reinforced and it lasts longer. Six mil polyethylene rips quite easily when someone crawls over it and, when glued or taped to a wall, it can also be easily pulled down.


6 mill is strong It would not be easy to tear it. You could puncture it very easy but the 20 mill would do the same thing. You can also use furring strips and Maze nails and pinch the plastic to the wall.
 
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Old 05-23-08, 10:05 AM
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6ml vs 20ml

I would like to use 20ml with mastic but as mentioned I can't find it, only the professionals carry it. I can't pay someone a fortune for something that will cost me a few hundred bucks and some elbow grease. My crawlspace is very old and worthless for storage, I just want the moldy smell gone, I only go down there when I need to add/repair duct work. I think I'm gonna go with 6mil, tuck tape the seams (overlap them 2') and tack strip the ends up. I can't use any adhesives becuase my wife is 6mos pregnant and I have a 2yr old daughter, plus I'd be trapped in an enclosed space and might be too high to find my way out lol.

Thanks for the help all, any other advice is greatly appreciated!

Matt
 
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Old 05-23-08, 10:19 AM
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6ml vs 20ml

I would like to use 20ml with mastic but as mentioned I can't find it, only the professionals carry it. I can't pay someone a fortune for something that will cost me a few hundred bucks and some elbow grease. My crawlspace is very old and worthless for storage, I just want the moldy smell gone, I only go down there when I need to add/repair duct work. I think I'm gonna go with 6mil, tuck tape the seams (overlap them 2') and tack strip the ends up. I can't use any adhesives becuase my wife is 6mos pregnant and I have a 2yr old daughter, plus I'd be trapped in an enclosed space and might be too high to find my way out lol.

Thanks for the help all, any other advice is greatly appreciated!

Matt
 
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Old 05-23-08, 10:22 AM
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You can put the crawl under negative pressure while you are doing any glue work to keep the fumes out of the home. Also you should clean up the mold before you put down the VB.
 
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Old 05-23-08, 10:22 AM
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6mil vs 20 mil

I would like to use 20ml with mastic but as mentioned I can't find it, only the professionals carry it. I can't pay someone a fortune for something that will cost me a few hundred bucks and some elbow grease. My crawlspace is very old and worthless for storage, I just want the moldy smell gone, I only go down there when I need to add/repair duct work. I think I'm gonna go with 6mil, tuck tape the seams (overlap them 2') and tack strip the ends up. I can't use any adhesives becuase my wife is 6mos pregnant and I have a 2yr old daughter, plus I'd be trapped in an enclosed space and might be too high to find my way out lol.

Thanks for the help all, any other advice is greatly appreciated!

Matt
 
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Old 05-27-08, 10:50 PM
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The specialized 6-8 mil stuff, (I've never installed anything as thick as 20 mil) isn't just thicker and reinforced, it's designed to seal the crawlspace but still allow it to "breathe." Think Gore-Tex for crawlspaces. Standard 6 mil poly doesn't do that. That's why it's so expensive.

Regardless of what VB you install, one of the most important steps is the surface prep. Spend some time picking up any loose gravel or sharp objects that might tear the VB, it'll make your installation last longer and keep you from kneeling on a rock hiding under the VB. (That is most unpleasant! )

Another part of a crawlspace encapsulation is sealing the vents in the foundation. Usually that's done with styrofoam board, cut to fit, and held in place with some silicone caulk. Although, if you use the 6 mil poly, you probably shouldn't seal them all. You might need a vent-fan that switches on and off based on the humidity. Or seal them all and install a dehumidifier.

To seal the VB floor to the VB going up the walls, I've found that the tape used by HVAC system installers works well. It's a little more heavy-duty and sticks better than regular duct tape. "Stitch" seams together so that it resembles the stitching on a football. The best way to fasten the VB up the walls is to use a sealant/adhesive - mechanical fastener combination. You might be able to rent a fastener similar to what the pros use... it's a cordless nailer with a magnetic tip that fires a small nail through a metal disk and into the mortar joints.

Before you do all that, I'd call around to see if any pest control firms or dedicated crawlspace specialists will do a free evaluation. They'll be able to tell you to what extent the crawlspace should be sealed... 100%, 80%... You need to make sure you're not simply sealing in the moisture, otherwise your problems get worse.
 
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Old 06-02-08, 11:00 AM
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this site has a material that they sell, with an adhesive to hold it on the wall, no special tools, or nailing into your block or foundation. It works great, and has a much higher puncture and tear resistance than anything on the market.

I have used it, and it works great. Its also treated so it won't allow mildew or anything to grow on it, and break it down.

Yourcrawlspace.com

If you call or email them, they are really helpfull and will let you know exactly what you need.
 
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