Ideally, in a shop where multiple people are working, you want an isolated pad that is the foot print of machine and quite thick. You isolate it with rubber or similar. Nardini calls for 2 feet thick. If you are making a finish pass and someone drops a hammer on the floor, it can show up in your finish. My shop is a one-man show. I chose to just pour the whole shop 13" thick (worked out to the trucks loaded with 10 yards of concrete. I had a bunch of steel left over from a big church job so I just put a bunch in the floor. 10years and I don't even have a hairline crack yet.
