Maybe, maybe not. Some of the import stuff is pretty nice, despite what some people say. So was 6" deep enough concrete? Danged if I'd trust that. I plan to mark my floor, bust up where the lift towers will go, dig it up and pour probably 12" footers. It's all in the installation. I know a little about it. I had a friend who installed lifts for a living. His business was "Rack Man Installations". Poor Jeffery, he had a debilitating stroke about two years ago and he died last year. I miss my buddy. He knew how to install shop equipment right.
