4-Post Lift Slab Versatility - New Construction

[rmckee]

We're in the permitting stage of a new 24x40 garage here in North Carolina. I have plans for at least one Bendpak HD9 4-post lift. The Bendpak site calls for 24x24x12" footings at each leg base in new construction, or 4.25" at 3500 PSI for existing slab.

I would like the versatility to A) move the lift around to facilitate projects and have some flexibility to layout, and B) have the ability to add another lift down the road if I wanted to do so. With that all in mind, it seems like it'd be more worthwhile to be spending money on beefing up the entire slab versus just doing the footers. I called Bendpak and talked to someone there who basically just agreed with my builder's idea that 6" slab + rebar would be substantial enough for the versatile plan. I was not really reassured by the Bendpak rep's easy agreement.

Anyone here have experience with making a more versatile slab for these kinds of scenarios where I don't want to have to commit to one lift In one place forevermore?

Thanks!

 

[GRivera]

Seems weird the "existing slab" requirement wouldn't be enough for a new slab. Many 2-post lifts have similar requirements to the listed specs for the "existing slab." 6" and rebar should be more adequate for residential use.

 

[Yankeefarmer]

Those specs sound more like they are for a two post lift. Look here:

Frequently Asked Questions about Car Lifts

A collection of frequently asked questions about car lifts from our customers who have purchased or plan to purchase BendPak equipment.

www.bendpak.com

 

[rmckee]

Those specs sound more like they are for a two post lift. Look here:

Frequently Asked Questions about Car Lifts

A collection of frequently asked questions about car lifts from our customers who have purchased or plan to purchase BendPak equipment.

www.bendpak.com

I've seen that one, but also found this info sheet that spells out much more complex requirements!

 

[sz0k30]

There are a hell of a lot of 2 post lifts on standard 4" concrete, including mine. 4 post lift shouldn't even require that.

 

[cstmg8]

If it helps, I wouldn't hesitate to move a 4 post lift all over my 5" slab with rebar grid. I'm confident in the packed substrate under the slab. How many points of contact would your truck have if pulled into the garage?

 

[wssix99]

Anyone here have experience with making a more versatile slab for these kinds of scenarios where I don't want to have to commit to one lift In one place forevermore?

Yes. If you don't have a post-tensioned slab, aren't putting in radiant heat, or embedding any other utilities in the slab, this is a very simple thing to deal with.

We're in the permitting stage of a new 24x40 garage here in North Carolina. I have plans for at least one Bendpak HD9 4-post lift. The Bendpak site calls for 24x24x12" footings at each leg base in new construction, or 4.25" at 3500 PSI for existing slab.

Where did you get this information from? The HD9 instructions give one spec for the floor. 4.25" of 3000 psi concrete, cured for 28 days. THIS is what you need to build to. Anything else (engineering-wise) is a waste of money.

New car lifts DO NOT require "footers" and are not designed for them. The base plates they come with are made for flat slabs sitting directly on the ground. Lift manufacturers do also give specs for repair slabs, which are deeper sections of concrete keyed into larger, substandard slabs. These allow people who have existing slabs that do not meet spec to cut out sections and enhance them to handle the lift. These are not "footers" and do not mechanically function as such. They are also not appropriate for new construction. For new construction, you just need to follow the spec in the instructions. ^ (I assume the 24X24X12 thing is Bend-Pak's repair slab spec for 4 post lifts?)

This all being said, the BendPak spec may not be enough to give you the quality in the slab you are personally looking for in your garage. All basic slabs will require saw-cut control joints to handle shrinkage cracking in the slab. Generally, these cuts are 10'-12' apart. You should plan these out ahead of time because we assume that each of these cuts has a crack inside them and (That's what they are for.) BendPak dictates that your post legs should not be within 6" of one.

Rebar generally serves no structural purpose in a residential slab. It's only there for crack control and helping to buy insurance that cracks will not develop outside your planned control joints. With very large amounts of rebar in the slab, you can space your control joints further apart or eliminate them entirely - but that adds considerable cost to the slab and requires some engineering.

Also, going far over that 4.25" of concrete doesn't give you anything in a residential setting unless you have a lift that requires a thicker slab. If you choose to use rebar in your slab, you need to increase it proportionally with the concrete depth to keep the same crack control, so adding depth to a reinforced slab increases cost by more than just the cost of the concrete!

I called Bendpak and talked to someone there who basically just agreed with my builder's idea that 6" slab + rebar would be substantial enough for the versatile plan. I was not really reassured by the Bendpak rep's easy agreement.

Yea, this is kind of like asking a proctologist for an eye exam. It's not what they do and they probably shouldn't have ventured to give you guesses for answers.

 

[wssix99]

BTW - Having a concrete finisher that knows what they are doing is key to getting a quality floor. The control joints I mentioned above should be 1/4 the depth of the slab and I almost never see anyone go that deep. (When you go thicker on the slab, this becomes even more of a problem!!!) Many contractors also wait too long to make these cuts. They need to be done as soon as the concrete sets up.

We have some members here who have experienced out-of-boundary cracks in their new slabs because their contractors half-assed this or waited several days to go back and make these cuts. "Little" details on this stuff are actually a really big deal and matter a ton.

 

[Yankeefarmer]

I've seen that one, but also found this info sheet that spells out much more complex requirements!

If you read the bottom of that sheet carefully, it says the specs that have you concerned are for new, stand-alone concrete and don’t account for the support from surrounding concrete. They are listed as minimum slab width and length. In other words, if you were setting a four post lift on a dirt floor, this is what you should have. My iPad wasn’t cooperating in copying just the portion to which I am referring.

 

[wssix99]

I've seen that one, but also found this info sheet that spells out much more complex requirements!

Ah - yes. Pages 2-4 are for repair slabs. It's confusing because they use the word "new" when talking about something that's really old and existing. Page 1 is what applies here for new construction.

 

[rmckee]

Thanks all for the quick replies. Someone from Bendpak just called me to follow up on Friday's call and pointed out the same info that two of you just found, that the footers are basically for putting a lift into a dirt floor barn and needing to rest the legs on something stable. I am surprised that information isn't listed much higher on that PDF form I found to clarify the data contradiction from everywhere else on the website. The word "new" really throws it for a loop.

The person there said that going to 5" with wire mesh or fiber mesh would be suitable for my plans, and told me to bring that back to the structural engineer for clarification in the design.

 

[rmckee]

Yes. If you don't have a post-tensioned slab, aren't putting in radiant heat, or embedding any other utilities in the slab, this is a very simple thing to deal with... this is kind of like asking a proctologist for an eye exam. It's not what they do and they probably shouldn't have ventured to give you guesses for answers.

Appreciate the detailed response. No radiant floors, and plumbing will likely be brought out of the structure above ground level. Sounds like it really shouldn't be too complicated.

 

[wssix99]

Thanks all for the quick replies. Someone from Bendpak just called me to follow up on Friday's call and pointed out the same info that two of you just found, that the footers are basically for putting a lift into a dirt floor barn and needing to rest the legs on something stable.

This isn't correct, either. If a Bendpak rep really said that, they should have their phone taken away and be forced to sit in the corner. (The printed instructions are technically correct and this is not what they say, at all.) If they are giving advice to people like this, someone could be seriously injured. [If one were to put this lift on a dirt floor, a continuous flat slab would need to be poured that extends 6" beyond each leg. All of the floor, concrete scenarios Bendpak and other manufacturers give include a continuous mass of concrete between lift legs.]
word "new" really throws it for a loop.

The person there said that going to 5" with wire mesh or fiber mesh would be suitable for my plans, and told me to bring that back to the structural engineer for clarification in the design.

The extra concrete doesn't do anything for you in this application. So, if you want to save some money, you can go back to 4.25" or even 4". If you read into the detailed Bendpak installation instructions, they give a detailed narrative about drilling holes, bolting, not drilling through the slab, and then needing enough depth so that one DOES NOT drill through the slab. (contrary to advice you might see in other threads on this site)

If you aren't going to bolt this lift down, the extra depth isn't providing that benefit to you. This (relatively light) lift also doesn't stress the slab out any more than a car sitting on top of it, so you also don't need any extra "strength" in the slab. The four post lifts (especially when they aren't bolted down) don't put much stress into the pad, contrary to what two post lifts might impart.

 

[1984shovelhead]

Good luck with bendpak bought 2 4 post lifts from them and 2 rolling jacks the customer service people I spoke to are chrome plated assholes should look into serving fast food.

 

[bjpil007]

This isn't correct, either. If a Bendpak rep really said that, they should have their phone taken away and be forced to sit in the corner. (The printed instructions are technically correct and this is not what they say, at all.) If they are giving advice to people like this, someone could be seriously injured. [If one were to put this lift on a dirt floor, a continuous flat slab would need to be poured that extends 6" beyond each leg. All of the floor, concrete scenarios Bendpak and other manufacturers give include a continuous mass of concrete between lift legs.]
word "new" really throws it for a loop.



The extra concrete doesn't do anything for you in this application. So, if you want to save some money, you can go back to 4.25" or even 4". If you read into the detailed Bendpak installation instructions, they give a detailed narrative about drilling holes, bolting, not drilling through the slab, and then needing enough depth so that one DOES NOT drill through the slab. (contrary to advice you might see in other threads on this site)

If you aren't going to bolt this lift down, the extra depth isn't providing that benefit to you. This (relatively light) lift also doesn't stress the slab out any more than a car sitting on top of it, so you also don't need any extra "strength" in the slab. The four post lifts (especially when they aren't bolted down) don't put much stress into the pad, contrary to what two post lifts might impart.

This isn't correct, either. If a Bendpak rep really said that, they should have their phone taken away and be forced to sit in the corner. (The printed instructions are technically correct and this is not what they say, at all.) If they are giving advice to people like this, someone could be seriously injured. [If one were to put this lift on a dirt floor, a continuous flat slab would need to be poured that extends 6" beyond each leg. All of the floor, concrete scenarios Bendpak and other manufacturers give include a continuous mass of concrete between lift legs.]
word "new" really throws it for a loop.



The extra concrete doesn't do anything for you in this application. So, if you want to save some money, you can go back to 4.25" or even 4". If you read into the detailed Bendpak installation instructions, they give a detailed narrative about drilling holes, bolting, not drilling through the slab, and then needing enough depth so that one DOES NOT drill through the slab. (contrary to advice you might see in other threads on this site)

If you aren't going to bolt this lift down, the extra depth isn't providing that benefit to you. This (relatively light) lift also doesn't stress the slab out any more than a car sitting on top of it, so you also don't need any extra "strength" in the slab. The four post lifts (especially when they aren't bolted down) don't put much stress into the pad, contrary to what two post lifts might impart.

This is really helpful info, thanks. I'm building a new 26 x 28 garage and plan to install an Advantage DX9000XLT 4 post lift, and my architect has been insisting on 12" footings at post points, and bolting down; however, Advantage is saying exactly what you're stating here so I feel better pushing back.

Only question -- is there any downside to putting a nice epoxy coating on top of the 4" 3500PSI concrete (in terms of the lift?) Cracking, etc.?)

 

[finn]

Personally, I would be reluctant to put a shiny floor covering under a lift unless it had some anti slip components in it.

 

[nafterclifen]

Personally, I would be reluctant to put a shiny floor covering under a lift unless it had some anti slip components in it.

Haha, this made me laugh. Do you really think a lift is going to slide on a floor? They're not light.

 

[kelpaso1]

No he's talking the area under the lift where oil and AF spills can make YOU slip.

 

[finn]

Haha, this made me laugh. Do you really think a lift is going to slide on a floor? They're not light.

No, but you will, when you slop oil and coolant on the shiny floor.

Unless it’s a showroom, and not a shop, I guess.

 

[firebirdparts]

It's not actually necessary to provide any special features to the slab. You just want good and solid underneath, 4.25" and 3500 psi. Way more than enough.

 

[nafterclifen]

No, but you will, when you slop oil and coolant on the shiny floor.

Unless it’s a showroom, and not a shop, I guess.

Ah, ok - I misinterpreted (sorry). I definitely agree.

 

[Falcon67]

Don't have any anti-slip additives under mine - called "watch where you step" and clean up spills.

4", 2 post, 4000 PSI, no special footers under the lift. Also consider that a 4 post has nearly twice the floor bearing area as a 2 posts, so I'd not have any problem moving it around a shop with a normal "4 inch slab".

 

[R. Deschain]

Those specs sound more like they are for a two post lift. Look here:

Frequently Asked Questions about Car Lifts

A collection of frequently asked questions about car lifts from our customers who have purchased or plan to purchase BendPak equipment.

www.bendpak.com

Agreed. My 2-post sits on 24" footings with rebar in them, but that seems way overkill for a 4-post.