I am a contractor in the Westchester, New York and Fairfield, Connecticut areas and I was wondering if anybody had any info on the exterior sheathing that was used in the 50’s and 60’s (maybe earlier too) that was sold under the name Celotex? It is dark brown/black waferboard material about 7/8″ thick. I never gave a second thought to it until recently where we are doing new siding/windows. I was going to rip it off (as usual) and plywood the exterior/housewrap/etc. Does it have any R value? It must have some. Does it make sense to leave it in place as a thermal break and plywood over it? The walls are 2×4, relatively new fiberglass insulation, vapor barrier. It would save the cost of removing it and one less thing in the landfill. I don’t know. Any thoughts????
Thanks
Replies
If it ain't broke, don't fix it comes to mind.
This sheathing was sold under several names, and was used well into the 80s (and may still be used in places). It's kind of halfway between cardboard and waferboard, with a dash of tarpaper thrown in. It's not real strong, but stronger than you'd think, and it's pretty durable -- stands up to weather (during construction) and leaks (afterwards) as good as anything. I don't know what the insulation value is, but it's better certainly better than OSB.
As was said -- if it ain't broke, don't fix it. The only reason for replacing it or plywooding over it would be if you want to install siding that can't be nailed into the studs.
Yes, it does have insulation value. Not too bad, really. Although I don't recall what it might be. My semi-educated guess would be maybe an R1.8 or 2 roughly for say 1/2" of it.
I think you can still get this stuff. I used it when doing my concrete slab. I required the contractor to use it to create a thermal break between the slab and foundation wall. It comes in like 4" wide strips and is great for control (or is it expansion?) joints in concrete.
I agree ... if it ain't broke ...