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Framing outer basement walls I think I made a mistake


Trickyrick's Avatar
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01-02-08, 10:45 AM   #1  
Framing outer basement walls I think I made a mistake

Hi guys I live in the north lots of snow in winter. Have a full basement. I want to put up drywall on the outside walls in the basement. Two years ago I framed them this way. On the back of the framed wall I put tar paper then stood the wall up against the foundation and nailed it in place I placed rockwool one bat at the top of the wall so only 1/2 the wall is insullated (upper)then I placed a vapor barrier over the wall. Just the other day I removed the vapor barrier and a few bats as I was going to wire some outlets and lights and finally install the drywall. I found that the inside of the tar paper was wet and so the bats were a little damp.
Did I construct the wall wrong or should I have left a gap between the back of the studded wall and the foundation and maybe only taken the tar paper down as far as the rockwool bat
Any suggestions.
Thanks
Rick

 
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01-03-08, 06:15 AM   #2  
The mistake is the felt paper. It's doing 2 things. It's acting as a vapor barrier on the cold side of the insulation (bad) and it's creating a double vapor barrier in conjuction with the second vapor barrier you layed over the studs (bad again). I've heard people refer to this as the basement diaper, sounds bad and it is. If I were you I would get rid of the felt paper all together, you say you live in the north so the vapor barrier should always be on the warm side of the insulation. I'm also not a fan of batt insulation in basements but I realize too that not everyone has the budget for styofoam or spray foam.

You say that you only have insulation on the top half of the wall? If your budget allows, I would continue it down to about 1 -1.5 inches above the bottom plate of the stud wall. Insulating the top half of the wall in not doing a whole lot if the cold air can travel down the wall and into your room, even if it is below grade. Hope this helps.

 
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01-03-08, 07:15 AM   #3  
To add on to what MN-Jay posted, you should check on local code requirements for placement of basement stud walls. In my area (NE) the studs must be a minimum of 1" from the foundation walls.

One of the benefits is that any moisture between the wall and the foundation won't get sucked up by the exposed batts.

 
Michael Thomas's Avatar
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01-03-08, 07:21 AM   #4  
"Basement diaper": new term to me, but all-too accurately descriptive.

 
25yrBuilder's Avatar
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01-03-08, 07:21 PM   #5  
in the area i`m in n.w. ontario, standard practice is to use tyvek in this area, writing on tyvek faces concrete wall for the reason that it is breathable one way and allows your insulated wall to breath out and does not let damp musty air from the concrete wall back to your insulation. at the same time not causing a vapour lock with combination of using vapor barrier on warm side. you would staple it to your plate that the joist are on, let it drape down to the point of it being under the bottom plate of you framed wall. tuk tape joints. much simpler and quicker than building paper. tyvek has a wax base to it so it repells moisture well, buiding paper on other hand is just that, paper, what happens to paper when it gets wet for long periods of time?

 
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01-04-08, 05:33 AM   #6  
Interesting approach, never thought of doing that before. I'm assuming you leave some sort of air gap between the concrete and the tyvek. Probably be the way to go if you are going to insulate between studs. Good post

 
Trickyrick's Avatar
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01-05-08, 09:46 PM   #7  
Thanks guys some good feedback. I like the suggestion with the tyvek would like something on the back of the studded wall to keep the rockwool bat in place Only one question why would I leave a gap with the insulation at the bottom If I'm installing an air tight (or as air tight as I can) vapor barrier on the room side of the wall. Also If I'm leaving an inch or two gab between the foundation and my wall would It be a good idea to maybe foam the gap at the top of the wall so warm air does not enter between the joists and down the back of the wall
Thanks again
Rick

 
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01-06-08, 01:50 PM   #8  
Posted By: 25yrBuilder in the area i`m in n.w. ontario, standard practice is to use tyvek in this area, writing on tyvek faces concrete wall for the reason that it is breathable one way and allows your insulated wall to breath out and does not let damp musty air from the concrete wall back to your insulation.
My understanding that except for StuccoWrap® and DrainWrap™, as long as they are properly lapped over itself and adjacent materials Tyvek does not care about orientation or face direction, see for example the DuPont™ Tyvek®: FAQ :

"13. Can DuPont™ Tyvek® be used with the lettering facing in?

DuPont™ Tyvek® HomeWrap®, DuPont™ Tyvek® StuccoWrap®, DuPont™ Tyvek® DrainWrap™ and DuPont™ Tyvek® CommercialWrap® are equally effective in both directions..."

http://www2.dupont.com/Tyvek_Constru..._builders.html

 
Gotassman's Avatar
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01-15-08, 04:28 PM   #9  
Here's a link that may be of use. Government of Canada publication.

Quite a lot of detail and there are some good sub-links also.

http://oee.nrcan.gc.ca/residential/p...ent.cfm?attr=4

 
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01-19-08, 04:37 PM   #10  
I live in Northern Michigan. I agree with not wanting a double vapor barrier (very bad), but I have always thought that the "vapor barrier on the heated side of the insulation" rule had an exception: when the framed wall is against a concrete wall. In this case I would think you would want the vapor between the concrete and the wood frame, then of course, your bat insulation would be the kind w/o paper. This keeps everything nice and dry in the wall and also allows you to build your framed wall with all white wood (except the bottom plate) since the vapor barrier would not allow the white wood to actually touch the concrete. Thoughts?

 
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