OSB Panel
Oriented strand board
"OSB" stands for oriented strand board. It's a type of engineered wood panel that is made from wood strands that are glued together.
It's a cheap alternative to plywood. And weaker than plywood. Comes in 4x8 sheets.
References
Sauna Roof Underlayment
From Felt to Rubber
✒️ Posts,
🔥 Sauna
It was ~50 degrees out so the rubber wasnt very sticky with the OSB panels. Yes, I made sure to clean the panels off as best as I could. Using the leaf blower to blast off as much dust as I could. I walked along the rubber to smoosh it down where I really needed it to stick.