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 2×2. In addition, they aren't treated, but neither are the 1×3 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.)?
Best Answer
This is related to your question, but something I felt like commenting on: since your CMU exterior walls are covered up with vinyl siding, you have a perfect opportunity to insulate your house, which should give you quite a lot of bang for buck given that it currently has none. Remove the vinyl siding (carefully), cover the CMUs with 3+ inches of rigid foam or mineral wool boards, and then re-install the siding right over that. The difference in comfort and utility bills should be dramatic.