Lift Owners: Question about Concrete Floor

Drill a hole to check the thickness of your concrete. If it is not thick enough you can add plates at the posts, but check with the manufacturer first.

 

I recently installed three AC Lift single post lifts. The requirement was for a four inch concrete slab to allow for the bolt sleeves to be sunk correctly.

I wouldn't take a chance with a lift. If you have less than a four inch slab, I would cut and remove a 2 foot by 2 foot square of the existing concrete where the lift post(s) will go and pour a new four inch slab. It's relatively easy to do and you can rent a concrete saw from Home Depot or else just hire a specialist concrete cutter to come in and do it for you.

 

unless you think you have a sink hole under your slab, the worst its going to do is crack the concrete slightly. . think about the footprint where your tires sit on the concrete already, the 4 post sits on a few sq inches more, and adds about 1400lbs to the load. unbolted , i think that most pads by code have to be 3 inches, most are 4 which is fine.

 

John,

I have an office in Millburn. I can send one of our engineers by to check out your slab. PM me.

DMAX

 

I am not far away (bergen Cty) and thinking of putting a 4 post lift in as well.

 

fyi - im very happy with my bend pak 9 9k lift . i just put it together , fast free shipping, great telephone support , ALI certified . 2350.00 on sale now delivered.
http://www.asedeals.com/contactus2.html

 

Darron, you wouldn't be "poor" if you didn't spend so much on avatars and golf carts.

 

I have never designed any structure with less than a 4" slab. Usually reinforced with 6x6 wire mesh or Nycon fibers. For a slab on grade you normally should not have a problem. I would get a 1/4" masonry drill bit 12" long and mark the depth of the slab on the bit. The hole can be spot filled or covered with the lift base plate.
BT

 

We recently poured 6" in anticipation of having a lift. I remember seeing that figure on some lift mfgr. site and our concrete guy said that is what we should do, too.

Chris

 

I will also be putting in a lift shortly and one lift manufacturer told me that some people don't bolt them to the floor. I had asked this question due to the fact I live in CA and the earthquake issue. The manufacturer said by not bolting them to the floor allows the lift to "walk" a little. I'm frankly scared of leaving the lift freestanding. Does anyone not bolt there lift down? I'm pretty sure I'll be bolting mine firmly into my slab.

They also told me if I bolt it down 4" slab is good.

 

great info everyone. what different lift manufactures do you guys use?

 

I was looking at Revolution and AC Lifts. I will probably go with AC Lifts. They've been great about answering questions, there prices seem very good and they're a sponsor here at fchat.

 

Assuming a 3000 lb car (unless you actually have a 7000 lb one) + 1000 lbs for a lift you will only experience point loads of 1000 lbs per post. Depending on how your floor was formed up, there may be some variation, but you should never have less than 3.5" of 3000 psi concrete. The wire mesh really doesn't add any significant structure to the slab, but it does hold the pieces together if it cracks. This along with a typical minimum soil bearing capicity of 2000 lbs psf should easily support a 4 post lift. It really gets down to how large the footprint of the posts are - they should have some type of plate between them and the concrete - as long as it is a minimum of 12" sq x 3/8" thick you should have no problem.

 

The PSI of the concrete is just as important as the thickness. Also it must be steel reinforced properly. I have seen posts go over in the Ford dealership.

I put a cubic yard of concrete, tested at over 4,500 PSI in the floor of my garage during construction. The whole floor is at least 5 inches thick throughout. The cost was relatively cheap.

My recommendation is to scoop out a yard of dirt and put in a yard of concrete of at least 3,500 PSI, steel reinforced. This would be for a 2 post lift. A 4 post lift could be less.

aehaas

 

Typical slab on grades are not reinforced. More important is what is under the slab. Normal soil at 2000 lbs min should be sufficient. However, because concrete is weak in shear there is the possiblilty of punch through should the material under the slab not be of sufficient bearing capicity or the point loading be too heavy/ concentrated and the concrete too thin. A yard of concrete would definately support a 4 point lift but it is WAY in excess of what is needed. The original question was regarding a 4 point lift. A two point lift is an entirely different issue - you have not only the weight of the lift and the car but also overturning moments and other considerations that are way beyond the average person to calculate - at that point they really need to contact a structural engineer and not a Ferrarichat webb site..

 

Most garages are 4" floors, not many 2" and same with 6" not many unless a lift or heavy equipment was planned.

Most (maybe all) 4 post lifts require 4" concrete

All the 2-posts that I looked at required 6"

I went with 4-post for other reasons then concrete thickness and I am very happy with my 4-post. My wife and I assembled my 4-post lift in roughly a day, a few hours one afternoon and a few hours next morning. And NO my wife is not some 6ft muscle thing, she is a petite 5'2. I don't think one guy could do it very easily but the second guy(gal) does not need to be all that strong, the 2nd person is just there to help align things and of course supervise. A engine hoist does all the lifting.

 

I also live in S. Calif. and my 4-post is NOT bolted down. My reason was that I got the caster kit but the casters were useless in my cramped garage. Don't know what is best, bolted or not and I am sure you can get equal arguments either way. Mine is not and you are welcome to drive up and see it (ignore the mess, please)

 

I appreciate the invite and the feedback. I'll let you know.

 

Just passing along my personal experience. I poured a 6" floor w/3500psi and rebar at 12" intervals for a 9000lb.max cap. 2 post. Might have been overkill but in 8yrs of service no cracks. Regards, Vern

 

My concern with just cutting and pouring 2' x 2' x (4", 6", etc deep) squares would be that now you have 4 areas of the garage slab that are independant of each other.

Not knowing your particular situation, but any seperate areas of concrete that are not "tied" together are going to move and expand at different rates depending on their mass, moisture level, age, etc.

If you are going to cut out sections and pour some deeper areas I would make sure to drill into the existing concrete cross section (12" depth is code here) insert some re-bar into the existing slab, making sure to do it on all 4 edges, and cross the rods to each other and then pour your concrete... and don't forget a moisture barrier underneath. That's a lot of work....

Consult the lift company and see what they think. But it sounds like most people are comfortable with 4" depth. It's still important to find out if you can. If the house was built 25-40 years ago I would suspect that the slab is pretty thik (4" plus). It hasn't been until recently that builders have really pushed the envelope because of time pressure and cost constraints to try and save a buck by making the garage slabs thinner, etc..

If you still aren't comfortable with 4" thickness, I'd look at bolting some 3/8" or thicker steel plates, (12" x 12" or larger) to the floor under the pad of each lift before I cut into the floor. That to me would help spread the weight of the lift, thus reducing the PSI...but that's just me, I'm not structural engineer.

See what the company thinks and get an opinion from a local concrete guy.

Good luck.

 

My 4 post lift is not bolted down either and it has been through a few earthquakes with no problem. I even park the f car under a 63 Buick Riviera.

 

My garage wasn't that tall so two post lifts were not my best option. I got the bend pak pit lift which will crank the car up about 30 inches or so and is so far sufficient for any task I have tried. I haven't actually bolted the lift pads down so that I can move them around to suit me and it seems to work just fine. Right now I'm driving a '95 M3 (yeah, yeah, don't start..) but until I can trade that ride (it's actually a great car for what it cost) for a sweet 308GTB or better yet a 308QV GTB (if you are selling one feel free to contact me) I don't want to permanently affix the lift pads. The bend pak equipment is great in my opinion and ASEdeals.com is a good place to deal with.