Can I use untreated no, sealer varnish or finish on some black ash ¾ inch by 4 by various lengths Tung and grooved boards, to line a SAUNA? Because I have some and can not use it in the spot intended. I always thought to use cedar, been told red wood. Just looking for the one reason to rule my cash of black ash out for good or not. Expansion problems, allowing mold and mildew, staining and cleaning questions have been debated with no truly knowledgeable conclusion. Thank you .oh ya what is the relative value of a slab of wood, believed to be Australian gum wood that measures apox.2 foot 8 inch /4 inch by 8 feet. Ruff cut with irregular 8 foot sides air dried for at least 20 known years. And is very heavy, Already located in USA .castile table in the ruff .thank you.