Two post lift concrete thickness

[planecrazy]

I'm unable to come up with an answer after searching so I thought I'd ask.

I'm in the process of building a new home south of Atlanta. We should be pouring the garage floors this coming week. I'd like to thicken a portion of the floor to accommodate a two post lift. At the moment, I'm leaning towards a Max Jax but any lift is down the road. I just want to be prepared for the future. It's a lot easier to do it now.

So, my floors (yes, I have two garages) will have 1/2" rebar on a 24" square and will be 5" thick. I'm thinking of thickening the concrete to 8" thick for a 4' wide swath across the middle middle of each.

Just looking for a reasonableness check.

 

[vhol5]

My 9000 lb 2 post only requires 4"...

 

[fnieto]

You din't state the weight capacity of your future lift. This will determine thickness required.
I have a 10K two post (fixed) lift that required a 4" min. I went 5" with steel and fiber knowing I would have fork lift traffic.

 

[planecrazy]

The Max Jax has a 6000 lb capacity. I can't imagine lifting more than that.

 

[c4cruiser]

When I bought my MaxJax, I started to drill hoes for the wedge-style anchors and found that the garage floor area where the posts would be was anywhere from 1-1/2" to 3" thick, in spite of the fact the plans called for a minimum 4" thickness. So much for the contractor paying attention to what the subs were doing.

Because the floor also had some small cracks where the posts would go, I decided to have two 4'x4' sections cut out of the floor and had two pads poured. Each pad was 12" deep, used a 5000psi mix, and rebar was used to tie the new pour to the old floor. I also had rebar placed in the poured area and carefully mapped the location of the rebar prior to the pour. That kept me from possibly drilling into the rebar later on.

I also decided to use 7" epoxy anchors rather than the included 4" wedge anchors. I had read a number of posts about the wedge anchors not seating properly and some even pulling out. With the epoxy anchors, it's important to completely clean the holes!! When you think they're clean, clean again. Repeat. It's also very important to make sure the holes are drilled vertically!

 

[pattenp]

If you look at the MaxJax site you'd see what the concrete requirement are.

From Dannmar...
"Most residential or commercial foundations are strong enough to support a MaxJax™ lift. The minimum requirements are 2500-3000 PSI 4" thick concrete. Be sure to check your floor on the possibility of it being a post tension slab. In this case contact the building architect before drilling. Visually inspect the site where the lift is to be installed and verify the concrete is in good condition. If your concrete has cracks or other defects, please consult with a certified contractor before proceeding to install the MaxJax™ lift."

 

[rburke65]

Well you should be fine with the 5" floor thickness all over. But personally, I like the 8" thick by 48" wide idea. Good luck!

 

[nehog]

When I bought my MaxJax, I started to drill hoes for the wedge-style anchors and found that the garage floor area where the posts would be was anywhere from 1-1/2" to 3" thick, in spite of the fact the plans called for a minimum 4" thickness. So much for the contractor paying attention to what the subs were doing...

I had a guy come to do my slab, but to save money I did the site prep. I did what I thought was an acceptable job--he looked at it and immediately said "Not good enough, do it over!" I spec'ed a 4" slab but he felt that there was too much variation in the thickness for his liking. So back in I went with the loader and re leveled it. Once I was done, there was less than an inch using the laser level, throughout the slab. (I did make it marginally thicker where the lift was to go...)

 

[C2 Turbo]

I recently poured concrete for my 5 car garage and called 2 top notch lift companies inquiring about the concrete thickness.

Both companies said, for any residential lifts (I inquired about 10,000 lbs), 4" at 3000 psi is plenty so I went with 5" at 4000 psi, which I thought was fair.

I guess I would do 8" or more concrete thickness, if I was in an armored core and had contract with my unit on servicing their tanks at home, otherwise, I would not waste any money on any thing more than 5".

 

[wssix99]

I'm thinking of thickening the concrete to 8" thick for a 4' wide swath across the middle middle of each.

\

This will increase your chance of getting cracks around the lift, so the best thing to do is have a consistent thickness across the slab.

Since your reinforcing (it is designed to control the tension caused by shrinkage of the concrete as it cures) is consistent throughout the slab, the rebar will be working harder to control the additional tension in the thickened area. If the change in thickness is abrupt across the cross section of the slab, your chances of getting cracks in that area will be greatly increased.

If you gradually increase the change in depth over a larger area, that will be better, but the safest thing to do is to have a consistent depth across the entire slab.

5" is plenty thick. The challenge is (with the variability in placing concrete) to get the actual depth you are paying for. For some reason, our concrete guys almost never give us more than we pay for here... IMO - The best thing you can do is be out in the middle of the pour, measuring the depth with a ruler as your company does the placement.

 

[Flanders]

4.25" floor slab, MaxJax wedge-it anchors worked perfectly.

 

[6768rogues]

My 9000# two post lift called for at least 4-inches of 3500# reinforced concrete. I used 5-inches of 4000# concrete with #4 bars every 24-inches in both directions. No problems in the 15 or so years the lift has been there.
Use at least what the manufacturer of the lift requires. Also, be sure to prepare the area well so you have a uniform thickness of concrete. We spent a day preparing my floor using #1 crusher run and a jumping jack. The stone surface was as smooth and uniform as the finished concrete. The floor measured for 26 3/4 yards of concrete. I ordered 27 yards and there was about 2 wheelbarrows of material left over.

 

[Tony_F]

Pad info that Bendpak gave me is attached... YMMV.

One of the things Bendpak was concerned about is having a nice even/level area for the arms to swing out and car to sit on. Many folks don't pay much attention to that. If the front or back of the vehicle is lower then its possible with a low slung car, the arms will not go underneath it on one end.