Concrete slabs and 2 post hoist

[Bernica]

Originally Posted by muzzza

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

Muzzza is right on point! I would do this and maybe even more if I was using a 2-post. I would also drill into the sides of existing slab and use rebar to dowel into them. Use epoxy grout when you insert the dowels, then order a good mix of 4,000 PSI or higher mix for the footings. And chuck the anchor bolts and use long J-bolt anchors. The deeper the footing, the more the safety factor.

My 2 cents