I'm putting a 2 post lift in my garage,....however, my concrete floor is bad.

[smithenhiven]

I put up a new steel garage building over the summer, I tore down the old block garage, but left the concrete floor and footings, and went up with it from there.  The floor was poured back in the 70's, it's cracked in many places, and it's even heaved up in certain spots.  I couldn't afford to have it all ripped out an re-poured, so I left it be (it looks like it's long since done moving).  It serves it's purpose and is great just for having a "space", but now that I want a lift, I have to address the floor.

My plan for installing the lift, is to cut out two 4 foot square sections in my floor where the posts are going to sit, then dig down several feet, and pour concrete piers reinforced with rebar and fiber.  I could even back dig under the old slab another foot or so, effectively creating a lip that would hold the pier block if it ever tried to move.  I'll also drill some horizontal lag holes into the existing floor in the newly cut "side walls" of the pier holes, and pound in some self grabbing anchor bolts which will stick out into the new concrete; which once the pier holes are filled, I'm hoping those anchor bolts will somewhat lock the new piers with the old floor. 

Does anybody see any problems with my plan?  Anything you'd do different?  Only other thing I might try to do is pile drive an I-beam or something into the bottom of the pier holes down another few feet into the earth but sticking up through the hole to terminate just under the surface of the new concrete.  That might be over kill, I don't know, I just know I don't want this thing to move, ever.

[JB400]

I think you're over doing by quite a bit.  The one lift that I put in was bolted to a 4 maybe 6 inch thick floor.  Of course, it was a new floor.  I like your idea of  4 ft. square piers, but I'd only make them 1 ft. thick max. You could probably get away with just 10 in. just fine.  I'd also do just 2 mats of 1/2 inch bar in each pier on 12 inch centers.  Make sure your base is packed solid before you put your bar in.  When you order your concrete, ask for 6 sack cement.  Also, don't add too much water.  The drier you pour it, the stronger it is.  Wait a week before mounting your lift.

You can anchor it to your existing concrete if that's what you desire.  It'd make sure that the piers and the slab stay the same height.

[smithenhiven]

Thanks for the response.  We are going to laser shoot the heights of the new piers to insure they're exactly the same.  If anything, the piers might extend above the old slab slightly so that they're level with each other, and not following any slope of the old slab.  My thinking on anchoring the piers to the old slab, if those piers were to tilt for any reasons (mainly due to the load of the lift), hopefully being pinned to the old slab would prevent any front to back, or side to side movement.

[birdsandbees]

Do yourself a favour and just install it to the existing and build a truss across the top to hold the posts.

I installed mine to my 6" thick floor a few years back and it tried to crack out towards an expansion joint and lifft the floor on one side, so I built a truss across the top out of 2 x 2 x .125 tube and some plates bolted to the post top bolts. Hasn't budged since and I've had some pretty heavy 3/4 ton trucks on it.

[smithenhiven]

I would love to just install it to the existing, but I don't know if it's got a high PSI rating, or if there's even rebar in it.  I can tell just by looking at it, that it was a quick hack job that wasn't done very well (looks like they finished it with a rake) and the fact that it's cracked up so bad and heaved in certain spots has me concerned to the point where I'd just rather have the posts of the lift sitting on something new that I know I can trust.   

[birdsandbees]

My floor pour was the best concrete money could buy in 1995 and 6" thick. It still cracked towards the expansion cut lifting my wife's little Sporttrac and then about 8 feet back into the slab in one spot. I sledged metal plates into the expansion crack to retain the "break away" and built the truss, it hasn't moved since with about 400 hours logged on the hoist.

Just cautioning that a 4' square may just crack anyhow. My rear bolts are the ones that cracked the slab, not the front ones, and they are a good 20" from the expansion cuts and on a 4' slab you'd be closer than that with all bolts.

[FJMG]

Your solution to brace the top is a good one, however, in my region, the cracking you have experienced is less of a probem with the concrete and more of a problem with rebar placement. In concrete design, the tensile strength is commonly regarded as near zero, that is why steel reinforcement is specified.

When a two post is planned, then two layers of rebar mat in the lift area should really be considered, one near the bottom (as is typically installed) to handle vertical loads in the same direction as gravity, and then a second mat near the top to handle the upward lift of the slab that is created by loading a two post lift even slightly askew.

While the OP may consider to leave the original slab and utilize top bracing, the structure should be given consideration since off-center loading on a two post (especially an assymetric) can introduce large unwanted horizontal loads on a light-duty building.

To the OP....
Any major reason you cannot use a four post?

Unless, of course you already bought the two-post.

[Dino]

I know nothing about floors but would it be unreasonable to take one of those monster disc cutting things to the floor to remove a section so you can pour a new, strong, and level section just for the lift?

[smithenhiven]

To the OP....
Any major reason you cannot use a four post?

Unless, of course you already bought the two-post.

I already bought a 2 post, and did so because I like the idea of a two post so the wheels and suspension can hang free.

[smithenhiven]

I know nothing about floors but would it be unreasonable to take one of those monster disc cutting things to the floor to remove a section so you can pour a new, strong, and level section just for the lift?

Um yeah, that's exactly what I outlined in my first post, lol.

I was looking to see if folks agree my plan, and/or could offer suggestions on what additional steps to take or eleminate anything as overkill.

I appreciate the ideas so far, thanks everyone.

[Dino]

I know nothing about floors but would it be unreasonable to take one of those monster disc cutting things to the floor to remove a section so you can pour a new, strong, and level section just for the lift?

Um yeah, that's exactly what I outlined in my first post, lol.

I was looking to see if folks agree my plan, and/or could offer suggestions on what additional steps to take or eleminate anything as overkill.

I appreciate the ideas so far, thanks everyone.

And I read it when you posted that. I'm an idiot. Ignore me.   

[lukedukem]

Read this thread. I think it is what your looking for.

http://www.dodgecharger.com/forum/index.php/topic,69766.0.html

Luke

[Kern Dog]

I've worked as a Carpenter/Framer since 1986. I was the guy that wanted to be the best and the fastest on the job. ecause of that, I rarely paid attention to the other trades along the way. I'm talking concrete, plumbing, electrical, HVAC...I wish that I had my eyes and ears open all this time because the knowledge would have helped when I started doing my own projects.
I built a workshop out back in 2006. Again, aside from wood framing, my experience was limited. I knew that I wanted a 2 post lift so I made the ceiling 10 feet high at the walls and vaulted to the middle. For concrete, I erred on the side of extreme caution! The slab was 4" thick everywhere except where I had figured the posts would sit. There I had the concrete guys dig 24"X24" footings 18" deep. The holes had rebar tying into the regular part of the slab as well. Later I read that most car lift manufacturers require only  6" slab.
I have zero cracks and do not expect to see any!

[garner7555]

I already had 4" slab in my shop and decided to put in a lift.   It already had the brace that runs from one post to the other ( I wouldn't consider buying one that didn't have that).  I also used some 2"x2" angle and some 3" channel and bolted/welded the post to the steel structure of my shop roof to relieve the stress on the slab by preventing off-center loads from trying to pull the post out of the slab.  It has worked out amazingly well, but you need to make sure your building is strong enough to support this.

http://www.gregsmithequipment.com/Shop/2-Post-Lifts
This link talks a little about the 2 styles of lift.  I would not use what they refer to as a baseplate lift.  I have seen them fail too many times.  You need that brace running across the top.        

[smithenhiven]

Read this thread. I think it is what your looking for.

http://www.dodgecharger.com/forum/index.php/topic,69766.0.html

Luke

That was a cool thread, thanks for linking me to me, I really like how the guy put lights in his floor, I would have never thought to do that.

[smithenhiven]

I already had 4" slab in my shop and decided to put in a lift.   It already had the brace that runs from one post to the other ( I wouldn't consider buying one that didn't have that).  I also used some 2"x2" angle and some 3" channel and bolted/welded the post to the steel structure of my shop roof to relieve the stress on the slab by preventing off-center loads from trying to pull the post out of the slab.  It has worked out amazingly well, but you need to make sure your building is strong enough to support this.

http://www.gregsmithequipment.com/Shop/2-Post-Lifts
This link talks a little about the 2 styles of lift.  I would not use what they refer to as a baseplate lift.  I have seen them fail too many times.  You need that brace running across the top.        

The lift I bought was used "Rotary" 2 post, and it has the connector beam/brace at the top connecting both posts.

I was hesitant to buy a used one, but I think I got a few year old good quality name brand lift for less money than I would have spent on a lesser quality Chinese new one.  Plus it was installed and fully functional, so I got to see that it worked and had no leaks before I bought it.

[FJMG]

I already bought a 2 post, and did so because I like the idea of a two post so the wheels and suspension can hang free.

I hear you, I did the same.

You are on the right track by using mass of concrete to resist overturning of a vehicle that is not perfectly centered on the lift.

One thing to keep in mind is that if you calculate the volume of concrete in two 4x4x4 cubes that you have planned you will find that you will have almost enough to pour a large percentage of your floor 6 or 7 inches thick.

Whatever you do you may want to consider using a template and casting some bolts or threaded rod into the fresh concrete.

[Charger-Bodie]

When we re poured the floor in the shop, we got a template of the hoist foot print and made a steel under structure for under the concrete with bolts welded to it to set the hoist onto.

[smithenhiven]

I already bought a 2 post, and did so because I like the idea of a two post so the wheels and suspension can hang free.

I hear you, I did the same.

You are on the right track by using mass of concrete to resist overturning of a vehicle that is not perfectly centered on the lift.

One thing to keep in mind is that if you calculate the volume of concrete in two 4x4x4 cubes that you have planned you will find that you will have almost enough to pour a large percentage of your floor 6 or 7 inches thick.

Whatever you do you may want to consider using a template and casting some bolts or threaded rod into the fresh concrete.

My garage is 35x50, I roughly calculated needing 5 yards to do the piers as I'd like.  If I were to do my whole floor at 6 inches, I'd need well over 30 yards.

I like the template idea, makes more sense to set the anchor bolts in with the concrete pour, rather than drilling and using the self anchoring ones after the fact.

[areibel]

When we re poured the floor in the shop, we got a template of the hoist foot print and made a steel under structure for under the concrete with bolts welded to it to set the hoist onto.

I helped a friend install his, he did the same thing.  He used two pieces of 18" Sono Tube probably three feet long into the ground, and he dug out for a form 3 feet wide between so that it goes past the outside of each tube.  Built the rebar brackets for the bolts and aligned everything, then used a couple long pieces of rebar to tie the two brackets together and held it in place when he poured the concrete.  This was on a gravel/stone floor, it's in and he left tails sticking out on each side so he can dig it out and pour up to it when time and money permit.  It's basically a 6 inch slab that's roughly 12 by 3 with the tubes under the legs, and the frost hasn't moved it yet

[garner7555]

I already had 4" slab in my shop and decided to put in a lift.   It already had the brace that runs from one post to the other ( I wouldn't consider buying one that didn't have that).  I also used some 2"x2" angle and some 3" channel and bolted/welded the post to the steel structure of my shop roof to relieve the stress on the slab by preventing off-center loads from trying to pull the post out of the slab.  It has worked out amazingly well, but you need to make sure your building is strong enough to support this.

http://www.gregsmithequipment.com/Shop/2-Post-Lifts
This link talks a little about the 2 styles of lift.  I would not use what they refer to as a baseplate lift.  I have seen them fail too many times.  You need that brace running across the top.        

The lift I bought was used "Rotary" 2 post, and it has the connector beam/brace at the top connecting both posts.

I was hesitant to buy a used one, but I think I got a few year old good quality name brand lift for less money than I would have spent on a lesser quality Chinese new one.  Plus it was installed and fully functional, so I got to see that it worked and had no leaks before I bought it.

I bought a used one as well.  I got a Bend-Pak 15,000lb lift.  I didnt need one that heavy, but I farm and it doesn't hurt to have one over-sized because I might use it for tractors or large trucks one day.   You did the right thing to get a good name brand, Rotary will hold up great for many years!      

[JB400]

Just a heads up. Concrete is approx. $100 a yard and 1/2 inch bar is almost $10 a stick (20 ft.) in my area. (west central MO)  I don't know if price is much of a factor, but might help you figure out your best option.

[69rtse4spd]

www.concrete calculator.com. Just remember, you only want to do concrete once, so do it right, don't go cheep, it will only cost you in the long run & look like shit till you redo it. If money is tight then just do the area where the post will sit. Can do the rest of the floor later as funds dictate. The rest of the shop floor does not have to be as thick, depends what you are going to put on it. The sub-base & wire & rebar are cheap compared to the price of concrete. All concrete cracks, control joints or not, you do not want it to heave that is where the wire & rebar come in. We have 18 inch thick concrete here at the plant, cracks to a cut, moves over 1 inch takes off again. That I will blame on poor sub-base prep. some spots have settled under the floor, it shakes as a fork truck goes by.  .