Slab problem for two post lift

[Jemezcrusher]

Came to this forum from the Trifive forum. Those guys say youse guys are pretty smart fellers.

The two post lift I have recommends 4.5" re-bar reinforced 3500 PSI concrete. I may have 4", but my psi is 3000 and I would bet is re-mesh, not re-bar.

My thoughts are to cut out two 4x5' squares where the columns for the lift go. I would dig them out to 8" depth, and put in two 8" pilasters about 36" down. I would drill holes in the sides of the opening every foot or so in order that re-bar can be epoxied in to tie in the old work with the new work. Pilasters would have re-bar in them and tied in to the new 4000 PSI 4x5' portions.

Is this enough?

Is it over kill?

Am I crazy?

Jemez (hay-mez)

 

[ms fowler]

Visit the website for the lift you are considering. They will probably address this in a FAQ. If not write and ask them their recommendation.

 

[12ozd]

Is this enough?

I would think so

Is it over kill?

Absolutely

Am I crazy?

probably

Did the exact same thing at work when we installed a lift.
Don't want to be the guy that has to dig that up.
Considering the requirements you posted from the mfg. I would say you exceed them.

 

[04fivefour]

Very curious of this as well, we plan on getting a lift in the next year or so and would need to do this to reinforce that anchor point.

 

[Denwood]

My slab "retrofit is documented here: http://www.garagejournal.com/forum/showthread.php?t=265806

One of the images I posted up (for a Mohawk 7000lb asym lift) dictates a 48"x144" slab that is keyed (no need to epoxy rebar dowels) under existing. I ended up doing a 14" thick version of below, so a very high safety margin for the MaxJax I was prepped for. The reference for the composited image I had posted is here: http://www.mohawklifts.com/consumer/library/Slab_Req-Reco_2-2010.pdf

 

[sqft]

Yes, thats about what I did for my Mohawk install. But it was 18" thick, rebar, and keyed. Probably way overkill, but I feel pretty safe when Im under a big car. I would not go with less than spec, what ever you do.