Thinking back to my pig building days (many asbestos type sheeting roofs), I found that the spray on insulation, whilst working fairly well, did cause some problems, due to no cavity, and also at times was difficult to keep dust free/clean. We found that using T&G insulation boards, with a cavity and a coat of paint gave a better surface to work with.
As to the floor, I laid a wooden floor in a garage that had a fall of 80mm over 6m. All I done was got my levels and then using a table saw, ripped joists at the various depths to meet level. This gave me all joists sitting on the concrete. I also had some thin foam laminate underlay left over from a job, I put that between the joists and concrete, that cut down noise from machine vibrations.
