# How to frame around concrete block half wall in basement



## Studly (Feb 27, 2009)

I had to take out some sheetrock in a basement closet where we had some water seeping in during heavy rains. We've fixed that problem from the outside, and now I have to replace the sheetrock and framing in that spot, which is up against a concrete block half wall (we have a walkout basement).

The concrete block half wall has framing directly attached to it and that holds the rolls of fiberglass insulation against the concrete blocks.

In addition to that, the previous owner of this house had some weird, unconventional framing built for the sheetrock about 5 inches out from the other framing that is against the concrete block. So there's this big gap of wasted space that I want to fix.

I'm in frigid Minnesota, so proper insulation is important here. I see that if you're newly framing a basement, most people recommend putting foam board insulation against the concrete block and then framing against that and adding the fiberglass roll insulation within that framing. 

But in my case, the outside wall already has framing against the concrete block to hold the roll insulation. Can I just use that framing to attach my sheet rock to? Or is it worth the extra work to pull that framing out, add a foam board against the concrete block, and then build new framing up against the foam board, where I'd add the fiberglass roll insulation and then attach the sheetrock? Any advice would be appreciated!


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## de-nagorg (Feb 23, 2014)

I would leave the framing alone, because when it was shot onto the concrete, they probably used a 22 caliber nail gun, and these are a real WITCH to remove. 

I would pit the foam in then the Fiberglass, or just spray foam the whole thing. 

Then rock it, and paint or panel, or what ever finish you prefer.


ED


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## concretemasonry (Oct 10, 2006)

I would also use the existing studs. I would forget about the fiberglass between the studs and fill it with 2" and 1-1/2" sheets of EPS foam board (not XPS!). If the wall has been shown to be water tight in the past, you can adhere the to the block with a thin bead of foam adhesive. If you wish you can rout out a chase in the foam and install cable and outlets (use protective plates over the cable locations at the studs). Then apply the sheetrock or other finishing.

The total EPS foam is far superior to the wall using the combination of foam and fiberglass. From a performance and practical sense, you do not even have to insulate a wall below grade as much at a wall above grade because the soil temperatures are far warmer the the air and especially wind chill temperatures. Snow cover substantially keeps the soil temperatures quite warm by comparison and at about 55", the average soil temperature in Minnesota is about 55 degrees in the middle of the winter.

Dick


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## Studly (Feb 27, 2009)

Thanks for the great tips, Dick and Ed! I don't believe there are any outlets in that part of the wall, since it's inside a closet, so the total foam idea should work out. I haven't worked with EPS (or any sheet foam) insulation before. I assume I can just cut the foam to fill each bay between the studs, and then fill the borders/gaps with expandable spray foam?


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## de-nagorg (Feb 23, 2014)

Correct. there should be no air gap anyway, but the heat might seep through a crack to the foundation, so spray foam filling is OK.


ED


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## Studly (Feb 27, 2009)

concretemasonry said:


> I would also use the existing studs. I would forget about the fiberglass between the studs and fill it with 2" and 1-1/2" sheets of EPS foam board (not XPS!). If the wall has been shown to be water tight in the past, you can adhere the to the block with a thin bead of foam adhesive. If you wish you can rout out a chase in the foam and install cable and outlets (use protective plates over the cable locations at the studs). Then apply the sheetrock or other finishing.


I took a closer look at the 5 foot wide section where I have to replace the sheetrock and it looks like, although there is not outlet there, there is an electrical wire that's running through the studs horizontally to the other outlets outside of the closet.

Is it easy to make channels in the foam to accommodate the wire? Or should I just do a combo of foam and fiberglass in the stud bay, since as you mention, Dick, below grade insulation isn't as important as above grade?


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## rpregs (Oct 2, 2014)

I agree with Dick. Underground we usually recommended only an inch of foam (1" eps). You are looking for a thermal break mainly when below grade. So you wouldn't have to protect your wall as much as above grade where air movement is greater. In my opinion, you are not getting much added value (cost of insulation vs. cost of heat) by adding more insulation.


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## Fix'n it (Mar 12, 2012)

concretemasonry said:


> EPS foam board (not XPS!).


why not xps ?


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## concretemasonry (Oct 10, 2006)

Sorry about the naming mistake. The EPS is just expaned beads that are pressed into a boards shape. The better is the XPs that is an extruded board that si slightly heavier and insulates better. The bead - board type does not insulate as well, is messy to work with and limits the adhesives that can be used because the good adhesive eat it up. Beadboard is made the same way as your typical coffee cups. Extruded polystyrene is a more rigid panel that can be sawed or scored accurately, is easy to work with and will accept many of the better adhesives you may have and can easily be shaved if you need a precise fit.

For my insulation of the rim joist(above grade), I just roughly scored and snapped 2" thick boards to give me a little slop in fitting and then put a bead of expanding foam around the space and immediately shoved the piece it and let the expanding foam hold and seal it firmly in place. This way I got sealing and adhesive immediately with what happen to be available. - No little beads from cutting flying around and sticking to everything else for weeks(I am lazy and don't mind over-insulating. I also used the same materials for the spaces between in a 1-1/2" thickness to put between the 2x2 studs glues/nailed to the concrete wall.

Dick


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## Studly (Feb 27, 2009)

For the expanding foam to go around the XPS boards (to fill the gaps), what's the best kind? I was thinking of getting the minimally expanding stuff like you use around doors and windows. Is that the best stuff for this use?


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## Studly (Feb 27, 2009)

rpregs said:


> I agree with Dick. Underground we usually recommended only an inch of foam (1" eps). You are looking for a thermal break mainly when below grade. So you wouldn't have to protect your wall as much as above grade where air movement is greater. In my opinion, you are not getting much added value (cost of insulation vs. cost of heat) by adding more insulation.


I've now installed 1-1/2" XPS foam in the stud bays, which are below grade. So that will be enough? Can you explain the "thermal break" you mention? Would this meet code for most Minnesota cities if I kept it as is, with only 1-1/2 inches of foam?

I have some extra XPS left over, which I could use up by putting on another layer in some areas, but don't want to waste that time and energy to do that if it's not going to give me much benefit.

Also, I've read that XPS foam is flammable. The area I'm installing it in is a few feet below our electrical panel. Is there any code requirements for how far away the foam board has to be from the electrical box?

Thanks much for all the advice and help!


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## rpregs (Oct 2, 2014)

A thermal break stops or reduces the amount of heat transfer through *conduction*. It slows the heat from inside of your house from going and heating up the soil on the outside of your house. A continuous layer of sheet insulation is a very good way of only heating the inside part of your house. If you have your studs tight to the block and only have the insulation between the cavities it still works but is not as good. The studs have a better ability to transfer heat across the wall system if they are in contact with the concrete blocks. Also putting white wood on any masonry is not a good idea due to moisture issues.

I don't know what the building code in MN states as far as insulation goes. Usually in a new house the amount of insulation required depends on how the whole house is insulated and constructed. In WI I have seen 1", 1 1/2", and 2" insulation on new home foundations.


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## Olcrazy1 (May 28, 2013)

In Cleveland here so it gets pretty cold also. I just finished my basement. I had it studded 1" away from the block and close cell spray foam at 2" thick all the way around from rim joist to the floor. Hell of a difference down there from last winter and this winter. cost $2 a square foot but well worth it. For a small area it won't cost that much and it seals much and is 100% air tight, water proof and vapor barrier.


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