I’m looking for a better vapor barrier than sheet poly. After tearing into wall that were ten years old I discovered the poly used as vapor barrier had deteriorated into flakes. Is there a better product for vapor barrier available. I plan to use a vapor barrier to prevent radon penetration under the basement slab so it will also have to have physical strength as well as a barrier.
Edited 10/1/2004 11:08 am ET by DIY Larry
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A GC I sometimes work with has stopped using separate VBs. He uses two coats of tinted VB rated paint.
He figures he has to paint anyway and having absolutely as close to the inside as possible keeps it inside of the dew point within the wall limiting the chance of condensation. He caulks around my electrical boxes and where the cable comes into the boxes.
He also figures any slight moisture condensation inside of the paint will evaporate very quickly compared to what happens to moisture within a wall. So far he has, discounting a query from the inspectors which was quickly answered by literature from the paints manufacturer, had no problems.
You could install ridgid insulation before pouring your basement slab. I think you need a minimum of 2 inch think Dow Blue Board ( or equivalent) so as to hold its shape under the weight of the concrete's psi.
Painting the finished slab with VB paint is also a very good idea.
If really worried about radon gas coming through slab... contact someone about installing radon gas abatment techniques...involves installing PVC pipe underneath slab in a few locations and having pipe come up through slab and this pipe exits out to daylight through basement wall. A fan assisted vacume device is permanently fitted into the piping run. Vacume suction supposedly wisks radon underneath slab out to outside of building...preventing radon build-up inside building. This device is wisper quiet.
There are contractors who specialize in this thing. It's very simple to install...especially in new construction. Cost varies...is all over the place depending upon area and reputability...so you gotta watch. Contact your local or county Codes office and ask them for references...they should be able to give it to you straight.
Davo
Tu-Tuff, made by Sto. It's 4 mil, and untearable by human hands.
Andy
Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Thanks for the tip on Tu-Tuff by Sto, Would appreciate any information on a source of it you might have.
http://www.efi.org
I've used those heavy duty green tarps with the nylon netting encased in the material for this purpose. Army Navy stores sometimes have the really good thick ones (thicker than the standard heavy duty green tarps they have at dome depot.
They are very tough, vapor impermeable and come in a bunch of sizes. Grommet holes on the edge can be screwed with washers to the foundation walls. I've seen one exposed to the California sun for 10 years around the corner from me and other than a little discoloration it still has integrity. I would think it would last for years when out of the UV exposure.
Wylie
Success = Work+ Risk + Luck, in that order. Muriel Seibert
I think that Resource Conservation Technolgies is another source. 410-366-1146Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Can I ask a stupid question? If a 2 mil poly vapor barrier is
disintegrating into flakes in 10 years, why wouldn't
4 mil or 6 or even thicker piece of poly do the same? Isn't
this a matter of quality rather than quantity?
I would guess that it's a quality issue. Cheap stuff doesn't last as long. Or maybe the existing vb was left in the sun for a while before installation? I think plastics become brittle due to UV, and to time, as the more volatile compounds evaporate. So, thicker should last longer in a linear sense, that is, 6 mil lasts three times longer than 2 mil. I'd guess that better might last longer than that.
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
In terms of permeability, perms, foils pretty much blow away just about anything. Essentially there perm rating is zero. Aluminum is the most common material.
This can oxidize given enough time. Mylar film covered aluminum is proof from corrosion and available but it isn't cheap. If you want to be stylish you could use the vapor deposited gold on mylar like they use on spacecraft. Good stuff, pretty strong, light, durable and a very good radiant barrier.
I once saw a small building that used stainless steel foil as a vapor barrier. It was built for a research project. No corrosion issues. Near perfect perm rating.
A 6 mil poly sheeting would be more than durable, especially under a floor slab. Most building suppliers stock it in rolls approx 10 feet wide. It'll last forever.