Existing framing over insulation blanket in a basement

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Posted by: from Kawartha Lakes
9/1/2015 at 2:28:00 PM

Hi there.

I see that a few questions about this have already been asked on this forum, but the difference here is that the framing is already in place over the builder's insulation blanket (and I don't want to rip the framing down). Here is an image to show how it currently sits:


If I want to put drywall up, should I cut the existing vapour barrier (make multiple slits in it), add additional insulation between the studs, and then add a new vapour barrier and then the drywall right against the vapour barrier? Should I just leave it as is?

A builder in my area says the space between the vapour barrier and the sheet rock in the current configuration will cause moisture issues in that open space.

My mother has spent a full year in the house, and there has never been any moisture (that we can see) behind the vapour barrier. The basement seems very dry.

Any suggestions?


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Date/Time9/1/2015 at 5:53:03 PM

Hello there,

The only reason the wall should have had double framing is for frost wall purpose, meaning that the wall would have needed plumbing installed because you cannot install any plumbing on any exterior wall directly against the concrete. If this was framed this way throughout the space, it was not necessary, Definetly do not breach your existing vapour barrier by cutting it. Your exterior wall was framed and insulated already and would have been ready for drywall install without having to add another 2/4 frame to it. It is always best to have a professional look at it and give you the best advice how to proceed.

I hope this helps!

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Peter in Kawartha Lakes
Date/Time9/1/2015 at 5:57:40 PM

Hi, Ana. Thanks for the response.

I should have been more clear. The blanket insulation is right up against the concrete. There isn't any other framing behind it. So. it is a concrete wall with the insulation blanket attached to it. The framing in the image is the only framing on the wall.

Sorry for the confusion!

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Peter in Kawartha Lakes
Date/Time9/1/2015 at 7:23:52 PM

The attached image may tell the story a bit better.

Thanks for looking.

Existing framing over insulation blanket in a basement
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Brian from Next Restoration in Rockwood
Date/Time9/1/2015 at 8:31:24 PM

Hi Peter You need to have a vapor barrier behind a warm wall I would put a vapour barrier behind the drywall and leave what is existing

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Peter in Kawartha Lakes
Date/Time9/1/2015 at 8:39:01 PM

Hi, Brian.

Is having two vapour barriers ok? Should I not remove or at least slit the old one?

Thanks for the help.

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Date/Time9/1/2015 at 9:06:48 PM

Only one complete vapour barrier is needed on the warm side of a wall, after plumbing and electrical rough in has been completed and inspected. Insulation comes next, vapour barrier over and drywall to complete. Not two V-barriers! Trouble!

More complete and definitive answers should come from your area building dept. or at least a qualified contractor in your area. I hope there are no other area's of concern, and I hope this clears it up for you now!

Paul Ambridge

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Date/Time9/1/2015 at 9:14:10 PM


There should be some space between the concrete, then the stud with insulation, then vapour barrier. Part of the reason is to allow the concrete (which is porous and has a moisture content) to air dry and adjust prior to entering the living area. You should only have one layer of insulation and one layer of vapour barrier (on the inside "warm" side of the wall. Then comes the drywall or whatever covering you choose.

Take care.


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Peter in Kawartha Lakes
Date/Time9/1/2015 at 10:43:21 PM

Thanks for all the help. I will be talking to a local contractor, but want to know the situation before he comes in. A bit of knowledge can go a long way!

I understand what people are saying, but I am still a bit confused as to what you think should ultimately be done. I fully understand that local regulations trump everything else, but am interested what you would do in your area.

Basically, do you think there is an issue having space between the vapour barrier and the actual drywall? As it sits now, there is 3.5 inches of space if I put drywall onto the framing as is. Is the suggestion that I cut out the blanket insulation, put in new batts between the studs (this will leave some gap between the concrete and the insulation), then put the vapour barrier on and then the drywall directly on top? I guess the biggest question is whether or not moisture will form on the back of drywall if the existing insulation is left in place with the framing between it and the drywall.

Sorry to keep beating this dead horse!

Thanks again for your help. It is much appreciated.

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Date/Time9/1/2015 at 11:55:31 PM

Never put two layers of vapour barrier. The point of vapour barrier is to allow air flow on one side and stop interior air exchanging with outside air. If you put two layers you trap the air and prevent air flow which when temperature levels change moisture will build and mold will form. If you wish to add insulation to any existing wall simply add insulation and never more vapour barrier. Insulation is to provide separation from differing temperatures. Vapour barrier allows air flow to keep things dry.

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Date/Time9/2/2015 at 11:02:00 PM

Hi Peter,

You actually have pretty good situation. The existing blanket is providing a thermal break between the concrete and framing. The other guys are right that you should only have one VB so you should slash the existing plastic and put another layer of insulation in. I would use roxul in your situation as it is R14 in 3.5 in. thickness. That should give you R20 + and then the new vapor barrier. Make sure you do the rim joist cavities as well. I have used 2 layers of R10 blue or pink Styrofoam. I cut them 1/2" smaller than the cavity and use canned foam to glue them in place. It makes for a pretty tight assembly and should kept the basement really comfortable.

Good luck with it!

Jim Kuzma

Kettleby Handyman

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Peter in Kawartha Lakes
Date/Time9/3/2015 at 12:04:22 AM

Excellent! I priced out that exact insulation product earlier today. I now have a plan.

Thank you to everyone for the help. This is certainly a very helpful forum!


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Date/Time9/9/2015 at 11:53:28 PM

What a load of KAKA...any of you guys actually know codes? or how to build?...the insulation nailed to concrete is a lazy cheap builder who did not want to install frost walls....code clearly states: there must be a frost wall with insulation and a vapor barrier on "warm side of room"...there must be min. 1/2" gap between insulated walls AND THE CONCRETE...concrete sweats and the insulation if tight to wall will get wet and inevitably MOLD..joist end also must be insulated and vapor barriered "by code"..too bad this person will now do it wrong :(

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