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I'm renovating my whole basement but I'm starting with the "cold" room as I'll be moving some mechanicals in there. The cold room is one of those old storage rooms people used to use as a pantry/larder or as a fridge/freezer in the winter. It sits right under the front porch, measuring 4' x 6' and with a ceiling height of 7' 5". It had a 1' x 1' vent to the outside but I've patched that closed already. The ceiling is a concrete slab (top step of the porch). Walls are concrete block.

My first thought is to glue 2" rigid foam to the ceiling. Then frame the walls with 2x4s leaving about a 1/2 to 1" gap between the frame and the wall. This would mean that the top plate would be in contact with the rigid insulation of the ceiling. Attaching the frame at the top would mean drilling through the insulation before hitting the concrete.

I could instead frame the walls first, attach the top plate to the ceiling directly and then insulate the ceiling with rigid foam.

I'd finish both by using spray foam to insulate the walls and use treated wood for anything that touches concrete. I would also probably use a sill plate in conjunction with the treated wood. Then use strapping on the ceiling to hold up dry wall.

Which would be better? I can see pros and cons to both approaches. Or should I do something different?

  • You may want to consider metal studs instead of treated wood. If you plan to hang shelves then you'll need to put in some backer boards. – Platinum Goose Nov 22 '17 at 16:22
  • I'd have no problem with metal studs (although I've never used them) but I plan to hang a tankless water heater on the studs. Would this be ok? Also, I already have the wood... – Zapho Nov 22 '17 at 16:29
  • If you decide on metal studs and need to mount the tankless heater then you should use a toggle bolt - see this thread diy.stackexchange.com/questions/37576/… – Platinum Goose Nov 22 '17 at 18:01
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I think I'd run furring on the ceiling first, then frame the walls up to that so you can nail the top plates into it and help support it.

Since you'll have spray equipment on hand I'd then spray the entire thing for maximum moisture handling and hang drywall (or something more robust).

  • Thanks, this sounds a lot easier than what I was planning. My only concern would be that there would be furring directly in contact with the ceiling slab with no insulation behind it (apart from maybe a sill plate). Would this reduce the overall effectiveness of the insulation? – Zapho Nov 22 '17 at 18:45
  • Somewhat, bit it's no different than about any exterior wall above grade. – isherwood Nov 22 '17 at 23:50

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