My 1970 Utopia has a galvanized steel 'belly pan', which I have removed during my frame-off restore. I plan to reuse it. On top of that, was a ~1/2 inch thick black fiberboard material that sits below the floor 'joist' system and the floor insulation.
I'm not sure what the fiberboard is and what to replace it with. I think it may be an asphalt fiberboard. Some posts online suggest it's a homasote product...?
I see a few products online at Lowe's and Home Depot (links below), but neither store in my State (Vermont) carry the products nor can even order it...
I can find basic homasote sheets that are not coated with anything. That looks like it would absorb water.
Would it make sense to try to use homosote but to paint it? Is there another material I should hunt for? I've heard of people using painted or marine plywood facing the street... in my case it would be sitting on top of a stainless steel pan and exposed to water in a few places where pipes penetrate it... seems like a recipe for any wood material to rot.
I don't know the answer to your question, but try this: Do a search here on VTT for fiberboard and look at the hits that come up. You will find information that might answer your question in other threads about the modern equivalent that can be used.
Thank you for your contribution to the board.
Last Edit: Jan 17, 2021 6:11:53 GMT -8 by Teachndad
"I get that queasy how in the hell will this thing ever go back together feeling.” - PT