2 post lift on existing 4.5" slab

[JKELLEY]

We are wanting to install a 6k 2 post lift in one of our shops for personal use. We really dont want to cut and repour and are considering bolting 3/8" plates down then bolting the lift to those. Each pad will be 21" larger front to back than the post pad and 3" wider one the sides. Basically the post pad is 18x18 and we are getting two plates 60x24x3/8" We will bolt the ends of the plates down one the ends then bolt the post to the concrete through the pads. Probably will go ahead and weld the posts to the pad as well.

Any thoughts on this?

The only vehicles that will be on the lift would be a Grand National or a 72 cutlass.

 

[ericm]

Many 10k two post lifts call for 4.25" of 3000 psi concrete. I have seen a few that want 6". Check the specs for the lifts you're interested in buying. If the concrete meets the spec then you don't need to do anything other than install it correctly.

 

[JKELLEY]

we bought a used older rotary. The guy had it mounted in some pretty low psi concrete that was probably 4" thick or less. When i disassembled it, most of the anchors either spun or pulled right out. The concrete we are putting this on is pretty high grade and is verified at 4.5". We will go ahead and plate it for piece of mind even if the specs call for 4.5". I have seen to many videos of lifts falling over from improper operation and my nephew will be using it quite often.

 

[ConCretin]

Honesty what you are proposing is an 'improper installation'. I'm not saying it won't work or even be stronger than the manufacturer's recommended procedure but unless you hire an engineer to determine that, you won't really know. I'm not sure what function the added plate is intended to perform. A lift doesn't need a larger footprint, it needs enough quality concrete for proper anchor installation. If your concrete is up to spec, I'd leave well enough alone.

 

[JKELLEY]

Totally agree with you ConCretin. My brother is an aeronautical engineer and this is his project going into one of his airplane hangers. The plates are to add stability and help distribute the load forwards and back in the event loading gets off a little. If this were my project, I would cut out 36" square and pour 30" deep, i would also be installing a 12k lift or larger. Then again, i am just a heavy diesel mechanic.