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I've tried finding a definitive answer but it's far more common for folks to have block walls in basements that need to be furred out, so the information deals primarily with that and I believe this is different.

Problem:

The original owner of the home I just purchased used a combination of 1/2" and 3/4" high-grade plywood as wall coverings. Some of it was furred out to accommodate a pocket door and electricity, but the entire section of the perimeter (exterior) cinderblock wall has the wood nailed/glued directly to it. The wood has no signs of water damage of any kind and the wall's exterior has vinyl siding.

Plans:

Ultimately I want to go with drywall. I plan to install furring strips to attach the drywall to. Originally I looked into the $.99 - 1x2s for price and space saving, but I imagine I'll break half of them when I start screwing the board up. Same goes for the 2x2. In addition, they aren't treated, but neither are the 1x3 strips I've seen being recommended (again in a different context).

I'm now thinking of using pressure treated 2x4s mounted wide-side-down just for piece of mind and plenty of space for shallow j-boxes. I would mount them 24" on center with either tap-cons or ramset. I plan to have the assembly entirely held by the wall.

Question?

Are there any moisture considerations when mounting furring strips to a cinderblock wall not in a basement but with an exterior side?

I've read it's always an issue mounting untreated wood to concrete or other porous material, but he amount of time - about 25 years - and the lack of damage make me question this.

Are there any other processes that can be used to accomplish this if it is a problem (i.e.; sealing the wall, painting the wood with a special product, etc.)?

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If there is no current problem, why not simply glue or screw the drywall to the plywood? –  bib Mar 4 at 19:41
    
@bib: I thought of that. The problem is the guy built out a bunch. For example the sink wall had a 4" chase behind it. So we wanted to reclaim space. When we tried to demo only the necessary parts we found the whole room was built like cabinetry, interlocking at the joints between the walls as well as the custom ceiling. I might have been able to do it with large amounts of time and patience; at least one of which I don't have. –  Chief Two Pencils Mar 4 at 19:51
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You not worried about insulation? You could just frame up normally using 2x2s. This would give you enough room to run electrical with shallow boxes. –  DMoore Mar 4 at 19:59
    
@DMoore: originally these houses had no wall or exterior coverings, so not really. I found that these walls have natural insulating qualities. I'm meeting an energy auditor in a couple days, I'll see what he says about that. So, you're saying instead of the cheap furring strips use normal 2x2 studs. Any thought on the moisture? Do you think the evidence is good enough not to worry about it? –  Chief Two Pencils Mar 4 at 20:04
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I would glue/nail down the top and bottoms and leave a very small gap. Also in my area 2x2s would cost about the same as a decent furring strip - although I am introducing top/bottom plate. –  DMoore Mar 4 at 20:20

1 Answer 1

You need to decide what you are hanging the drywall on.

Choices:

  1. Ramset framing members of whatever depth and economy you want to the concrete block. I'd be careful with ramset and concrete block. Light load shells perhaps. Tapconning on all those framing members seems expensive to me. I believe this is your main suggestion.
  2. Adhesive framing members to the concrete block. I wouldn't recommend this. You could have trouble getting a good bond and glue lifespans for the cheap stuff can be very disappointing.
  3. Build a standalone wall (I think this is what DMoore is suggesting) with a top and bottom plate and 'studs'. The studs could be 2x2s, 2x3s, 2x4s, etc.

Considerations:

  1. Really? You don't want to slip even a 1/2" of poly iso foam board into this system. R-value has diminishing return but when you have nothing, the ROI is great (if you spend money to heat or cool the structure)
  2. What climate are you in? It may be desirable to try to prevent interior vapor (is there a shower? cooking facilities?) from entering the wall system. I'd suggest you look at new smart vapor barriers but I'm guessing they are outside your project budget at ~$0.50/sf.
  3. In my area (CO), 2x2s and 1x anything less than 4 is garbage lumber and not actually priced that attractively. Here, 2x3s and 2x4s are far and away the best values.
  4. The problem with 2x framing members sideways is that you will be very close to 1.5" in thickness and your minimum thickness 4" square electrical boxes are 1.5" thick. You can obviously deal with via paper drywall shims or redwood lath strip pin nailed onto the 2x.
  5. If you go with 1x material, how would you put electrical boxes in the wall?
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One more alternative: Install a combined insulation-and-framing system (they typically glue to the concrete), and screw the drywall to that. Insulation is a good thing. The designed-in wiring races are also a good thing. I'm seriously considering doing that in my basement workshop; if I had concrete above ground I'd be just as interested there. (Deliberately not citing brand; several exist and I don't have direct experience with any.) –  keshlam Jun 3 at 20:03
    
Good suggestion. Not sure why I didn't think of that but cost of the convenience assembly could be a deterrent. If he is paying labor, the labor savings are likely worthwhile but if he is doing it all himself those items probably drive the cost too much. –  Keith Hoffman Jun 3 at 22:32
    
If you place any value at all on your own time, it really isn't clear that the modular solutions are significantly more expensive. Especially if, as I suggested, you may want to run wiring through that wall at some point. –  keshlam Jun 3 at 23:09
    
I think your suggestion is a valuable option. However, when I have priced these assemblies, they have been very expensive, required significant pre-planning and lead time, and had some design limitations (depth of framing, insulation and total R-value). If you know how to stick frame and insulate, it is potentially the fastest part of the project, at least compared to drywall and painting. I value my time and I still stick frame service cavities. –  Keith Hoffman Jun 5 at 8:21
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De gustibus. The best tool for a task is the one that accomplishes the task best for that particular craftsman. –  keshlam Jun 7 at 6:09

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