[jr68]

I have ordered a two post lift and it requires a 4" concrete base. I'm thinking this may not be enough strength to support the weight of a car or 1/2 ton pickup. Maybe I'm being too cautious but how about a steel plate under each post to distribute the weight ? Do you think I need it ? What thickness plate 3/4" or 1" , 12" square , 24" square ?

 

[wiskeesour]

Jerry, my bro installed a lift for upto 10K. said same for posts. but my bro put 6" of crete and a 24" 3/8 plate under it. works great. rest of the shop floor is 4". he lays concrete part time for contract labor. was worried about cracking....jm .02

 

[CDJr]

Not too cautious IMO. Id damn sure have more than just 4" of concrete under a 2-post.

 

[WildBillyT]

Not too cautious IMO. Id damn sure have more than just 4" of concrete under a 2-post.

I agree. Last weekend I drilled holes to bolt down a 2 post and they were probably around 4-6" in depth for just the holes. I'm pretty sure the floor I was drilling had 8" of concrete poured in the two "lift footing" areas.

 

[ldrisner]

The concrete put in a garage will generally be 3000 psi concrete. Do the math. A lot floors will be a higher grade.

4" is plenty.

 

[jr68]

The concrete put in a garage will generally be 3000 psi concrete. Do the math. A lot floors will be a higher grade.

4" is plenty.

So at 3000 psi surface , a 12"x 12" area will support 432,000 lbs. and two will hold 864,000 lbs. am I figuring this right ?

 

[Codi]

I would hate to keep tripping over metal plates on the floor.

 

[MrDanB]

JR,
Although the concrete thickness is a factor, I would put the same thought into what type of bolts you're gonna anchor it with! Just something that came to mind when I read your post.
Dano:beers:

 

[JD4020]

I have no experience with lifts, but what is the concern about the thickness? Does the extra thickness keep the bolts from pulling out? I agree with ldrinser, that you will not "crush or crack" the concrete from weight. Are you concerned using a floor jack? Same principle right. I regularly lift a 5 ton dozer on a 4" floor using a bottle jack.

What I have always wondered, is are the 2 post so well balanced that you don't have to worry about tipping or swaying, where the anchor bolts need to support the weight without pulling out..

That would be my concern, as opposed to the supporting weight of the floor.

Jon

 

[pro70z28]

Make sure the concrete is poured over a properly prepared surface. When I poured my garage I put down 12'' of C6 (same stuff used for road construction). Then,....Pack it pack it pack it. Like anything good preparation is the key. No cracks after 4 years. If you want it stronger add a little extra rebar in the post areas.

 

[jr68]

Gary , its an existing building with a 4" slab.

Jon, good point about floor jacks and weight.

Dano, bolts are a major component which I have covered big time ( they will hold )

great input guys

 

[Steptoe]

What I have always wondered, is are the 2 post so well balanced that you don't have to worry about tipping or swaying, where the anchor bolts need to support the weight without pulling out..

If you read the instructions on a 2 posters, the vechicle HAS TO go on the right way around...we have had several 'accident' in NZ where vechiles wher put on the wrong way and the whole thing has tipped over....
Workshop floors here (building regualtions) require between 5 and 8" of mesh reenforced concret, with compacted dry coarse underneath.
So think about what way you are going to install...drive straight in or reverse in.
Bottom line, it is no big deal to cut a over size hole and dig out extra deep... way over engineer....set the mounting bolts and plate flush when pouring the wheel barrow load of cement...
Then you will NVER have any doubt and piece of mind everytime u use it.

We installed a new 2x poster about 6 months ago in the workshop.

Regardless of the base, the tipping over issues have nothing to do with the foundations...its the geomertry of the arms.

 

[Brian Lewis]

If your existing floor is a POST TENSION SLAB as most foundations are these days then cutting holes to dig and pour deeper isn't going to work!!
I'd just reinforce with a larger metal plate if it was me, main bolts go thru plate into concrete. Probably should call the company who makes the lift..