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bcbud3 01-27-2010 08:12 PM

Proper way to frame in a concrete wall?
My basement has a 4' tall concrete wall around it (exposedIts about 7-8" thick. the house framing sits on top of this. (I think it's 2x4 framing). This leaves a concrete ledge of about 3-4". The plumbing runs along the face of the 2x4's. I would like to cover the concrete with drywall but i want to make sure it's properly insulated. What would be the proper method to do this? There is no moisture on these walls.

Bob Mariani 01-28-2010 06:48 AM

no moisture because the wall can breathe to the inside of the basement and is dispersed. Insulate the wall improperly and you will have moisture trapped in the wall. Read more threads on this site for finishing basement walls since this is thoroughly discussed many many many times.

bcbud3 01-28-2010 11:19 AM

I have searched and have come up with a couple of things. I can put XPS on the surface of the concrete. (Not sure of the thickness, some here have said 2" to prevent moisture, others have said 1" to allow breathing). Some have said glue to concrete others have said mechanically fastened. I don't have the room to build out with 2x4's. Can someone explain how i could build it narrower? Would i mount the strips right against the xps? Would i build it as if it was a 2x4 wall (floor board, top sill, etc). I read one post that said 1" gap is not needed (if your wall is straight and flush). Lots of conflicting advice....

I want to slap on some xps, mount a couple of strips and hang some drywall against it...

Bob Mariani 01-28-2010 12:27 PM

you can do it this way, not the best way. You will see different opinions because the walls need to be different for different climate conditions. You are in a cold area. The issue is that the air will always contain moisture. This needs to dry to the inside of the room. And in some seasons the air inside (warm) will move outside and hit a cold wall and condense. This is what you need to avoid. In your area you need 2" foam. This material acts as an air break and a capillary break. it will prevent the condensation issue. And it is semi-permable. So the outside to inside air flow is not restricted. But in your area you need a 6 mil poly vapor barrier on the warm side (under the drywall) So without an air space you have no where for any moisture from the outside or from the foundation/footer transition to disperse. Best to avoid any materials that are effected by moisture. Use only rigid or spray foam and metal studs, not wood and use denshield not drywall.

bcbud3 01-28-2010 06:44 PM

That is the first post i have seen recommended doing it this way. Not saying your wrong just wondering if any other opinions?

tpolk 01-28-2010 06:47 PM

bob's a pretty smart fella. I listen when he be speakin

bcbud3 01-29-2010 01:53 PM

Ok, i found this, would this be acceptable?

I will be using the xps foam sheets. In the installation part, would I skip running the plastic sheet down the face of the wall? Could i use vapour barrier against concrete and thinner sheets of xps? They say to leave no gap between the wall insulation and the new that also correct? How do i attach my new wall to the xps face? How do you finish the ledge portion (possibly run some xps along the ledge?)

Thanks for answering...

Bob Mariani 01-29-2010 03:54 PM

no plastic against the concrete. moisture from the wall must be allowed to dry to the inside, this will only collect mold if you do this.

This article has many errors... find better ones as www.

You need to cap the shelf with rigid foam and tape and or use spray foam to seal all edges and seams or gaps.

You need a minimum of 2" rigid foam to resolve the condensation build up on the cold concrete wall during the heating season

An older foundation wall is most likely not built correctly. As such damproofing and not water proofing was used. And no membrane to stop moisture movement though the footer / wall transition. As such some methods to install the basement wall will not work as presented since these issues are not addressed. This is why the air space is needed.

Use pl400 to glue the foam to the wall

bcbud3 01-29-2010 04:38 PM

I checked out your link. The diagrams shown for cold climate only use furring strips to hold the drywall directly to the xps and no vapor barrier. You are recommending I glue the xps, build 2x4 frame over that (with approx 1" gap), insulate with bat, vapour barrier and then drywall, correct?

Bob Mariani 01-29-2010 05:13 PM

correct. if using wood studs be sure to use a sill seal under a pressure treated plate

bcbud3 01-29-2010 07:49 PM

After looking things over and doing some measuring, by the time i do it this way i will end up with approx. a 10" ledge. If i wanted to run the studs right up to the floor joists(no ledge), how would i deal with the now 6" gap (exposed 4" ledge + 2" gap from foam) between the original framing and my new wall?

Bob Mariani 01-29-2010 08:03 PM

not sure what your are asking here. But another thing to consider is that the area above this shelf is most likely above ground. Above ground wall construction is different than the below ground wall we have been discussing. At the ledge you will want to air seal the internal wall cavity to completely block air flow from the below and above ground sections. The above ground section only needs the stud wall and R15 insulation, not the rigid foam. This stud wall will have a pressure treated sole plate over sill insulation with a top plate. Each stud is fastened to the sole and the top plate. Install individually 16"0c and level. So I see no issue with support or treatment needed for this shelf area or gap differences.

bcbud3 01-29-2010 08:23 PM

1 Attachment(s)
if i was to run my new studs up to the ceiling instead of ending them at the ledge, how would i handle the 6-7" of airgap between the 2 stud walls?

Bob Mariani 01-29-2010 08:25 PM

no need to worry about it. Or something more architectural. Offset the top and bottom sections and make the top section a built-in cabinet or shelving

Scuba_Dave 01-29-2010 09:58 PM

Did a basement ages ago with the ledge all around
Made a great place to set beers down :thumbsup:
Plus if you will have a (flat) TV on any wall you can build it out w/shelves etc so it looks built in

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