Question on Basement Wall / Foam Board

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Old 02-05-15, 10:33 PM
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Question on Basement Wall / Foam Board

Hello, My basement was previously finished with 1/8" paneling over 2x3 framing, but in some areas the paneling was attached to 3/4" planks that were secured to the foundation wall.

I've torn all the paneling out and I'm placing rigid foam board behind the gap between the foundation wall and the framing. My issue is where the planks are attached directly to the concrete. Some of that area cannot be properly framed without removing plumbing and other HVAC stuff. It would be very expensive, time consuming, and somewhat risky to move everything. I wanted to know if it makes sense to place foam board between the planks that are secured to the wall? If so, would I need to put a thermal barrier over that foam board? and finally, is there a thermal barrier besides drywall that would work?

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Old 02-06-15, 05:29 AM
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Sure sounds like it was framed wrong in the first place.
Should have been foam board on the foundation then a 2 X 4 wall framed in front of it.
That foam needed to be 2" thick.
With 2 X 4's there's room for the electrical boxes and the wires in the middle of the studs so they will not be hit by nails. They also would allow you to add R13 Batts.
Pressure treated bottom plate or at least foam sill seal under regular studs.
 
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Old 02-06-15, 06:09 AM
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If you don't put up a stud wall as Joe says, the way I would treat it is to put foam between the planks so that it's flush with the front of your furring, then place another layer of foam on top of that. Then I'd tape all seams, and foam the bottom edge with the floor. There should really have 2" of foam on those walls like he mentioned, so if you used 3/4" for the first layer, you'd want 1 1/2" foam for the 2nd... to put you over 2". 1" foam over the top would give you 1 3/4" which would be better than 3/4"... that only gives you 1 1/2".

Some people will tell you that the foam shouldn't be sealed tightly in case there is moisture. IMO that's a mistake, because NOT sealing it tightly has the potential to cause condensation. If you have a problem with moisture (groundwater from the exterior) then you shouldn't be finishing the wall in the first place.
 
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Old 02-08-15, 07:33 PM
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Here are a couple of pictures of the walls ... The framing was done by one of the previous owners and the lumber and depth varies. I plan on framing along one of the walls that has wood attached to the foundation, but the others would require a lot of work, moving an oil tank, plumbing, etc... I would prefer to find a material that I can attach to the wood that's already on the walls. It's just not clear what constitutes a thermal barrier. I contacted Ownen Corning, but their response basically said anything that's equivalent to 1/2" drywall would suffice. That doesn't really help too much, are there any fabric materials that would work? Name:  IMG_70741.jpg
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Size:  28.2 KBThanks for the responses.
 
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Old 02-09-15, 04:11 AM
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The method used to fur out the walls was old school, at best, and done by an amateur. Why drive holes in a perfectly non leaking basement wall/boat? You have little insulative qualities in the foam as it is presently installed, and certainly no vapor barrier due to the wood.

Although not very popular with DIY'ers, our advice is to remove the slats, consolidate your foam, tape it up to seal it and build a wall 1" from the foam using 2x4 lumber (pressure treated on bottom). You will now have an adequate wall with sufficient space to run your electrical and communication wiring.
 
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Old 02-09-15, 08:54 AM
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To move an oil tank, and the soil and vent pipes in order to properly frame the basement is just not feasible. I plan on working with the existing framing and insulating where possible.

Is there any material that can provide thermal protection for the foam board besides 1/2 drywall or 3/4" plank? A fabric would be the preferred material. I can't seem to find an answer to this question?
 
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Old 02-09-15, 11:25 AM
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I know of no "fabric" that is fire retardant other than carbon fiber or Kevlar, neither of which would be feasible. How much space does the tank and periphery take up? Can you not frame the remainder of the basement conventionally and make adjustments to the oil tank area?
 
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Old 02-09-15, 12:56 PM
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The bulk of the basement is framed with 2x3 and another portion with 2x4. I have been able to add foam board behind that framing and need to decide whether to use fiberglass insulation as well. The pictures I'm showing are the exceptions ... It initially had 1/8" paneling on the wall mounted wood, but I was thinking that foam board + paneling is probably not a good combo, so I was hoping to find some other material to use on there.
 
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