I really like the way this material looks as a flloor/ceiling. Could it also be used downstairs without plywood underlayment, on a post and pier foundation?
yes , I was talking to a mill and they wanted to know whether 2x6 were going to be one side good ( for roof decking or two sides good for a loft ( floor on top flat and other side good with groove). You can use 2x6 for higher spans than floor sheathing. Material wise will be more expenive than OSB subfloor plus 3/4" flooring