Vapor barrier

Started by rdzone, January 20, 2010, 04:51:34 PM

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rdzone

Seems like a simple thing, but I want to start putting up my 6 mil vapor barrier and wondered if anyone had any special tricks or suggestions.  Any secret ways to do corners, tape whatever.  Seems pretty easy, but I don't want to cause my drywaller (me) any problems later. Thanks.


Chuck
Chuck

rocking23nf



rdzone

I figured out the no holes part, but thanks for the reply.  I guess staples and tape is all it takes, as no one has any input.  Just thought I would check as it is always the simple things that bite you in the butt later.

Chuck

glenn kangiser

It should compress into a pretty manageable little bump under the rock I think, Chuck.

Working lately quite a bit so don't get to all of the forum anymore. d* 
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

Redoverfarm

I did hear that when the vapor barrier is put into the interior to allow an extra 2" at the bottom.  That will alllow you to put a sealer (caulk) along the floor plate/floor of the wall studs and then compress the barrier against that.  That seals off the gap if any are present or appear in the future.  All seams should be taped.  Better off  making the seams away from the corners and into the flats or either side.  The corners is the weakest part of the structure as far as vapor because there are multiple parts coming together at that intersection.  Make any sense?


rdzone

All,

Thanks for the pointers!
Chuck

davidj

I've been putting 1' square bits of 6mil behind my metal electrical boxes and was gonna tape the sheets to that to try and seal them better.  Is this sensible forethought or just a silly waste of effort?

Whilst on the subject of vapor barriers, we got our cabin sealed up around Thanksgiving.  We had minimal crawlspace venting at that point and what existed I covered up to keep out the animals and snow.  And I left the earth bare, figuring I'd sort out a vapor barrier once the plumbing and electrical was done.

Then I went into the the crawlspace a month later to work on the plumbing - the rim joist was soaking and there was mold on all of the engineered wood that was within a foot of the outside walls.  Water was literally dripping from the joists in some places.  It turns out that damp dirt, a 35F crawlspace and 25F outside walls was all the necessary ingredients for the World's most efficient water vapor and mold factory!

I cut the rest of the vents, put down 6mil polythene and taped it well, and a few weeks later everything is nice and dry again.  I'd recommend that other folks do this a bit earlier in the project - seeing all your nice framing go all green and blotchy is no fun!

rocking23nf

Metal electrical boxes have thier own vapor barriers, they are code here, they are made to fit around the box and are required on all external walls.