It appears that you are the proud owner of a lot of celotex.
Were it I, I would remove rather than cover, and take the opportunity to insulate.

Hi Lesnyc.

I'm not sure about the your walls, but I'm with Snoonyb on your ceiling: it's Celotex. That is, I agree that it's probably Celotex, but unless there's a compelling reason, I'm on the other side of the fence when it comes to ripping it out, not only because it's original, but also because the stuff is historically important as an example of an early 'green' building material.

The stuff was made from the cane pulp left over after sugar refining, which otherwise would have been burned. Instead, the Celotex company recycled it into an inexpensive & easy-to-work building material which came in handy after the war, when traditional building materials were still in short supply.

And rather than just being a cheap substitute for plywood or dimensional lumber in small-scale projects, Celotex was used in some pretty important applications. Because of its sound-absorptive properties, it was frequently used in large public buildings--theatres, churches & schools--where acoustics were important. A few years ago, they restored a big 193Os convetion hall in Atlantic City where it was used to cover the ceiling's giant barrel vaulted ceiling.

Anyway, if your cabin's a heat sieve & you need the insulation, that's one thing, but otherwise, I'd try to preserve the Celotex ceilings. At 5O years old, they're plenty historic in their own right. And while you're at it, if you can figure out how to do it, why not put up a few photos of your place up on the boards here, so that the folks who aren't familar with Celotex can see what we're talking about?

Regards,
MAGNAVERDE.

Oohh, please tell me more about this Celotex. The ceilings in the bedrooms of our house have approx. 3' by 3' boards held up by wood lathe strips. We are assuming it was put up there to cover up failing plaster or calcimine. We had thought they were plywood but I recently painted a bedroom and the boards are more like an old particleboard. I was a bit worried about asbestos since I was scraping the old caulking away from the boards.

There is a link above on my earlier post, and I have some photos.
I'm not sure if it's original to our house, which was built in 1945, because a few additions were done over the years. I understand the "green" significance of the product, and it is old-maybe not 50 years, but I am not loving it! Mine sounds just like yours Michelle, some of it is held up with lathe strips, and does look a bit like particleboard/paper. I'm leaning toward getting rid of it, maybe leaving it in one room where it is in decent condition...