[Detroit Bill]

Originally Posted by muzzza

Cantilever forces imposed on concrete slab can be quite severe - especially when you and the Mate are hauling and swinging on a gearbox, under a car 2.0m above your head !!!

" Tufflift" spec sounds minimal at best. I would cut slab out beneath each post ( say 800 x 800 - depends on anchor bolt layout )
Bore min 450 dia pier, down at least 900 deep. Toss in some reo ( 4Y12 cage would do ) and use nominated tie down bolts, with at least 300 embedment.
( anchor bolts supplied may not be long enough ) Hook tie down bolts into pier reinforcing with plate cleats or similar.
25mpa conc to pier, with a bit of F72 mesh to new slab infills.
Key new slab infill to existing slab if possible.
Make a dummy base plate in ply or something to get it all jigged up.

May sound extreme, but I had a good Mate killed under a hoist.
Distance to edge of slab may be an issue also ??

Murray QBCC Lic Building Designer

This sounds like a good plan. The idea of a lift is to feel good and be safe about it when you are under the car.