Making slab thicker for a vehicle lift

[Hobby_Man22]

So instead of making an entire 3000 square ft slab 6in I'm just going to go with 4in 4000psi because after asking on here most people say it's fine. Now should I make a section where the lift is going to go thicker or just go back later on and cut out a small section where the lift is and pour it thicker after the pour. I like the idea of doing it after that way the inspector doesn't question well what are you putting in this section that 6"? I doubt hes gonna like the answer when I say vehicle lift. Lol I guess I could say pickup truck. Lol

 

[Hobby_Man22]

Personally I'd rather just have the contractor go back after the fact and pour it exactly where the lift is going to go once all the inspectors have left.

 

[Hobby_Man22]

Maybe I'm overthinking this though, but technically a vehicle lift isn't supposed to be on a residential property if you read the zoning laws, not that these are followed but mine basically say you can only sit inside your house and be very quiet. Lol

 

[Lucid Moments]

When I had my slab poured I planned out where I was going to put the lifts and had the contractor prep areas 4' x 4' and 1' deep specifically for the columns. I am sure that when the lifts were installed they were not perfectly centered but I really doubt that matters.

 

[TobeyA]

^^^ That's what I did. The lift ended up almost perfectly centered on the thicker parts.

Would an inspector really notice a couple extra inches here and there? No permits for me, so no direct experience with that.

 

[Hobby_Man22]

I was just going to do like a 20x20 section

 

[NFH2740]

A four inch slab is adequate for a lift. If you must, include a footer of sorts right from the start. There is no need to cut a brand new slab.

 

[Hobby_Man22]

Not according to mohawk. A 10k lift calls for 6'' of concrete.

 

[merkyworks]

Seems a lot easier to do single pour and be done. Then having to come back, cut and re-pour.

If you have a general idea where the lift will be located on the 3k sq.ft. slab, just make that area 2” deeper (6” thick) and leave rest of slab 4” thick. Give yourself some sq.ft. buffer if your not sure of exact location.

 

[Retroman]

Going to be much cheaper to incorporate the footings into the pour. As a estimator and PM for a concrete and sawcutting company to come back and cut, demo, excavate, dowel and pourback for (4) 4' x 4' x 6" footings would be at a minimum $2600. Prices vary by region and local. We buy a lot of concrete so we don't get charged extra for short loads.

 

[pl_silverado]

Just make the whole thing 6” 4000psi with mesh. Buy once cry once.

Hell, I made mine 8” 4000psi w/ mesh and a grid of #4 rebar on 12” centers.

 

[seber]

As far as zoning laws, every state, every county, and every municipality has their own. Where I live there are zero restrictions. I can dump an old junk trailer on a lot and live in it. I'd check the local laws before I make a decision on the way to go.

 

[haveissues]

No way is the inspector going to see an area is 2" deeper and question it. If he does, tell him you are pouring an area thicker in case you end up with something heavy that you need to park. And I agree with you-4 " is not enough for a lot of lifts. My Rotary requires 4 1/4" minimum.

And if your project is getting inpsected the less the know about a lift the better.

 

[bluedog225]

Pretty sure you can have as thick a slab as you want. Don’t need a reason for the inspector. If asked, say I just like thick slabs.

Edit-with a 3000 sq ft slab, get a soil test and an engineer to design the slab. Then bump by 25% to account for contractor screw ups. No mesh. Use no. 4 on 12 by 12 centers and throw some no. 5 grids in wherever you feel the need.

 

[Hobby_Man22]

Contractor was going to do 3/8" rebar in 16" if I remember right. I'd prefer 12 honestly. That's a 4" slab.

 

[pbon]

Pour it now if you know where your lift will be. Light duty lifts may spec 4”. My Atlas BP8000 did. 10k lifts probably require thicker. Mohawk may require thicker for its A7 even though the weight rating is low because it does not have the upper cable cross.

 

[ConCretin]

Contractor was going to do 3/8" rebar in 16" if I remember right. I'd prefer 12 honestly. That's a 4" slab.

#3's at 16" is perfectly fine. In terms of resistance to cracking, reinforcing doesn't make a slab stronger. It simply holds cracks together. Make sure your contractor plans on putting the bar on supports. Don't rely on his assurances he'll pull it up as he goes. Despite his intentions, he probably won't. Congrats on the new shop and good luck with the pour.

 

[Walkers]

I vote for making a few square feet where you are going to put the lift deeper by a couple inches. No inspector will question it.

 

[Ign]

I also had them do a rectangular "trench"....it was actually like 12" thick LOL. It was a little larger than the overall footprint so I had a little wiggle room. Not necessary but we were pouring from scratch so not a big deal.

Just be certain you're getting a level slab. It can be difficult to convince contractors and local inspectors you DO NOT want a slight grade for drainage

 

[bluedog225]

Just to vent a bit and echo some of the above since I had a bad experience.

1. No way to know what is adequate or not without a soil test and engineer. No way. It may be well intentioned but it is all internet speculation. Don’t make this mistake.

2. The framing, plastic beams, rebar, and rebar supports all need to be 100% before you allow concrete. My guy said he would put put in supports and fix a framing issue, then just poured and walked away. Nothing, nothing you can do at that point to fix the pour. And if you don’t pay him, things can get ugly in the concrete world.

3. Triple check square and level before the pour. Get a pro to do it if needed. Laser levels, transoms, etc.

4. Extra thickness and rebar at the likely lift location costs almost nothing. Throw it on top of the rebar grid and tie in. The real expense will be the soil test, engineer, and materials they specify. And increasing the specs by a bit if you choose. Take pics before you pour….seriously, it all looks different after.

5. Get a friend or hire someone whose only job is to check in the concrete trucks and look the drivers in the eye and say “no added water.” Make them say they understand. Then your job is to turn off the water to the site until the pour is complete and watch the chute on every truck until they are done. Turn your back for a second and they add 30 gallons.

Hope it works out. First concrete job is a real learning experience. Unfortunately.

All the best.

 

[RAS61]

If you don't mind the extra cost I'd do the whole thing 6", doubt the inspector will notice or care, and if he asks any questions just say you like doing things extra safe (Code +1) and don't want to worry about cracks down the line. Making some areas deeper for footings draws attention and screams something funny's going on to me

 

[ConCretin]

To go back to the original premise that thickened areas of the slab are going to raise alarm bells that you might - Gasp! - install a lift. Is there really a place in America where you aren't allowed to install a lift for personal use?

 

[Lucid Moments]

Why do people keep worrying about an inspector. I thought the inspector's were there to make sure that building code is followed and the code is there to set minimums. If code calls for 4 inches and you go 6 the inspector won't care. That isn't his job. Zoning might, but that is a different department.

 

[Hobby_Man22]

I was just going to do a 20x20ft area in the back right corner where I would put it. That's an extra $1200 bucks

 

[csp]

I've never had to have a slab pour inspected, including when I built my home and later my shop.

Footers and stem wall rebar to follow with the engineered specs, absolutely, but not on a slab.

You might look into that before losing sleep over it.

 

[Hobby_Man22]

Just to vent a bit and echo some of the above since I had a bad experience.

1. No way to know what is adequate or not without a soil test and engineer. No way. It may be well intentioned but it is all internet speculation. Don’t make this mistake.

2. The framing, plastic beams, rebar, and rebar supports all need to be 100% before you allow concrete. My guy said he would put put in supports and fix a framing issue, then just poured and walked away. Nothing, nothing you can do at that point to fix the pour. And if you don’t pay him, things can get ugly in the concrete world.

3. Triple check square and level before the pour. Get a pro to do it if needed. Laser levels, transoms, etc.

4. Extra thickness and rebar at the likely lift location costs almost nothing. Throw it on top of the rebar grid and tie in. The real expense will be the soil test, engineer, and materials they specify. And increasing the specs by a bit if you choose. Take pics before you pour….seriously, it all looks different after.

5. Get a friend or hire someone whose only job is to check in the concrete trucks and look the drivers in the eye and say “no added water.” Make them say they understand. Then your job is to turn off the water to the site until the pour is complete and watch the chute on every truck until they are done. Turn your back for a second and they add 30 gallons.

Hope it works out. First concrete job is a real learning experience. Unfortunately.

All the best.

Are they still likely to add water if they use a pump truck?

 

[Hobby_Man22]

Talked to the concrete guy and he said he can do a 3x3 pad where the posts go.

 

[Ilikeike]

Not according to mohawk. A 10k lift calls for 6'' of concrete.

I'm assuming that is due to the fact they don't have the overhead support most of the cheaper ones do, which take a lot of the lateral load off the anchors.
Mohawks legs are beasty self supporting with lots of lateral loading when lifting a vehicle.. due to no overhead beam tying them together.
I cutout re-pored and keyed in the footing for my Mohawk lift, in accordance with their instructions.

 

[ConCretin]

Are they still likely to add water if they use a pump truck?

They are likely to add water no matter what. These days, no-one wants to deal with stiff concrete and they'll often add water if they can get away with it. A traditional mix design is based on a 4" slump, which is fairly hard to work with in a slab.

Having said that, there is nothing inherently wrong with adding water on site as long as the allowable water in the mix design is not exceeded. Rather than forbid the addition of water, better advice would be to instruct the driver not to exceed the the specified slump. If the concrete arrives at a 3" slump, it's not reasonable to ask your finishers to place it and you won't be happy with the job you get.

Better yet, order concrete with enough mid range water reducer to provide the slump your finisher wants so you don't have to worry about it. Water reducers are a chemical admixtures that allow for higher slumps without adding water that would weaken the concrete.

 

[bluedog225]

Agreed. Is OP really prepared to do a slump test at delivery?