Builder,
When we did my Brothers shop BenPak recommended 6" of concrete for his 2 post isometricle lift ..so we just to be safe dug down another 2" an flared it out in bought a 4ft circle where where the the posts were to set so they are setting on 8" of concrete with the regular 4" steel mesh as a reinforcement.
He uses his 2 post lift daily in his buisiness an there are no sighns of cracks or anything round the mount points after 2 yrs of heavy use.
Tim
