concrete pad for installing a 2 post lift

[bearskinner]

I am about a week away from FINALLY starting on the concrete floor in the shop. Approx how large of an area should be dug out 6-8"s thick for the posts on a 2 post lift? I am pouring a 24'x24' extension in the shop. I was thinking about 3' squares should be enough, but should I just make 10' wide trench about 3' Front to Back? Overkill? the rest of the floor will be approx. 4" with 5" at the edges, and 6" at the drive in door. Ive always believed overkill is under rated anyway

 

[kirkkw]

I have wondered if in your situation if it would be advisable to install the appropriate bolts in the floor when the concrete is poured rather than later drilling for and hammering in concrete anchors.

 

[Falcon67]

I would just pour that whole area/side/bay 6" and be done with it. 4" 3000 PSI is the usual minimum, so 6" would be plenty of "over done" and not having to hit a target. If you know exactly where it's going, then to REALLY overdo it, you'd carve out about 24" x 24" x 6 or 8" and run a 12x12 grade beam right through both pad areas.

 

[bearskinner]

I have wondered if in your situation if it would be advisable to install the appropriate bolts in the floor when the concrete is poured rather than later drilling for and hammering in concrete anchors.

That is what I was thinking also, but realistically I will be framing, insulating etc the inside of the shop, and a few other projects, so I wont be able to even think about purchasing a lift for another year.

 

[kirkkw]

That is what I was thinking also, but realistically I will be framing, insulating etc the inside of the shop, and a few other projects, so I wont be able to even think about purchasing a lift for another year.

I'm in the same boat 20-30 months out. I may make a gantry crane first to assist with unloading and installation of the lift.

 

[SwerveDriver]

I made my entire slab 5" thick with 2" foam insulation below that. In the areas where I planned to place the 2 lift posts I omitted the 2" foam (4'x4') creating two pads 4'x4' and 7" thick. Probably total overkill but worth it to me- the cost of the additional concrete was nil. The 4'x4' pad area leaves plenty of wiggle room when placing the posts.
--Don't forget to document the exact location of the pads either with photos or measurements or both.
--Be sure to avoid having expansion joints or saw cuts in that area.
Both sound obvious but things can get hectic on the day of the pour.
Best-
SD

 

[vision8]

Why pour two pads side by side ? I poured one pad 4 feet by 14 feet and 8 inches with the anchor bolts positioned to my lift layout; but I have in floor pex loops for radiant heat so did not want to chance hitting the lines after. Also installed a few anchor pods in the 30 x 50 foot slab ; the minimum I would put at least two per door opening to winch a vehicle into the shop or assist any moving via anchors. Made my anchor pods out of 6 x 6 inch HSS with 1 inch bar welded inside them.

 

[wssix99]

Approx how large of an area should be dug out 6-8"s thick for the posts on a 2 post lift?

Don't do this. It will make your floor (and lift) weaker. Best to follow the instructions and pour a flat, consistent slab. If this was a good idea... the manufacturer would give you instruction on how to do it.

For a new slab, flat and consistent is the strongest way to go. Pad pouring is for retrofit applications where you don't have a floor with the required thickness or crack/structural problems. Pads also have pin/key systems to integrate the pads with the larger floor, which you can not easily replicate during a new pour.


Will you be putting rebar in your floor? If so, the different thicknesses will cause you additional issues and can promote cracking. (Exactly the opposite of what you'd want.)

It's easy to assume that having "footers" for the posts is a strong and good thing to do. The vertical force on your slab from the two post lift is not really any greater than just having your car parked directly on the slab. (Your car's weight sits entirely on 4 tire contact patches and the weight of your lift sits on 2 base plates - which are larger and spread the forces out more.)

The forces of greatest concern for your slab hosting your 2 post lift are tipping forces. Having a continuous and consistent slab will give you the best control of any shrinkage cracking that may occur and the strongest slab for your lift.

 

[astroracer]

Like was said in one of the earlier posts. Minimum recommended thickness is 4" for 3000psi concrete. No need for anything different. As long as you stick with a 9 or 10K lift you'll be good.
My hoist is bolted to exactly that and has had an Astro van sitting on it for almost two years with no issues.
Mark

 

[stngfever]

When it was time for the floor in my 32x40, I did a 6' x 15' - 6" thick and remainder of floor 4".

The floor was done as one slab, then relief cuts we're done such that only one was made within the 6' x 15' section in the middle of the 15' width.

 

[AllenYo]

Vision8 - can you describe your anchor bolts a bit more? I'm not familiar with "HSS"