2 post lift and non structural concrete slab question

[roadrunner255]

Hello all,

12x40x48 post building moving along slowly.

Getting things together for a flooring quote. Slab will be non structural, and poured after the building is erected.

Plan on installing my bendpak 10k 2 post lift towards the center of the building.

Bendpak recommends a minimum thickness of 4.25 in. (108 mm) 3,000 PSI / 28 Day Aging and #6 Rebar (3/4"), and spacing of 12 in.

I was planning on using 6" of concrete, a contractor also suggested adding wire mesh as well.

Any comments?

Thanks!

 

[wssix99]

Can you share the passage you are reading in the instructions? I just read BendPak's instructions for the 10AP and they said 4.25", 3000PSI, 28 days and reinforced. (with no specifics) 6" minimum bolt spacing from cracks. (and joints in the slab)

- You need a 4" depth for the lift's anchor bolts and BendPak recommends a little more to make sure you get it. If you have less than 4", you will be in trouble. Even if you specify 4.25", best practice on this site is for YOU to watch the pour like a hawk stick a ruler in the concrete and make sure they give it to you!

- 3000PSI is a minimum, you can go with more. A higher PSI rating will have more cement in the mix and will give you a nicer finish on the floor.

- 28 days cure time is needed for crack control. No way around this minimum for any lift.

- The reinforcing BendPak recommends is insurance against cracking post-cure. It performs better than mesh. Mesh is less expensive, but you are rolling the dice a little in comparison. (#6 rebar is crazy, overkill and expensive. You should be able to reinforce a slab adequately for crack control with #4.)

 

[roadrunner255]

I opened a support case with bendpak and they referenced the 10ap for existing concrete in the following document.

BendPak lift install

Even ai is recommending #4 over #6.

Thanks

#4 or #6 rebar for non structural 6" concrete floor and a bendpak 10ap 2 post lift

Use #4 rebar (1/2" diameter) spaced at 12 inches on center in a grid pattern for a standard 6" residential or light-commercial concrete floor supporting a BendPak 10AP. [1, 2]

Why #4 Rebar is the Right Choice

• Overkill for the Application: #6 rebar (3/4" diameter) is massive, typically reserved for heavy commercial foundations, bridge structures, or massive industrial slabs. #4 rebar provides more than enough tensile strength for a 10,000-lb capacity 2-post lift like the BendPak 10AP. [1]
• Placement & Clearance: #4 rebar is much easier to handle, bend, and tie correctly. Crucially, it allows you to maintain proper concrete coverage above and below the steel (at least 2 inches of clearance) inside a 6-inch slab. Using #6 steel in a 6" slab crowds the depth and makes precise positioning difficult.

From: "Support - BendPak"
Subject: RE: Bolting lift to non structural 6" slab requirements

Hello,

If the slab is wall to wall and a new pour then 6 inches should be fine. I've also attached a link to our concrete slab requirements section of our website. This should help you answer any questions you may have. FYI use the chart on page 3 10ap, even though it says "pre-existing concrete foundation".

Car Lift Concrete Slab Requirements - BendPak

BendPak strongly recommends consulting a concrete specialist before installing a car lift. Review general slab thickness, strength and installation requirements before you begin.

www.bendpak.com

Concrete Floor Requirements - 2-Post and 4-Post Lifts - BendPak
Thank you,
T1 Parts and Technical Support Specialist

 

[firebirdparts]

Go for it. 6" is overkill, and overkill is good. I much prefer #4 rebar too, FWIW.

 

[matt_i]

They want a couple of straight parallel pieces to improve the "beam strength" between the posts (?)

There is a long history of litigation against lift manufacturers and they are squarely hoping you will issue them a get out of jail free card by diverging from requirements.

Id just do it despite the overkill. The concrete yard may be able to deliver what you need.

I'd be surprised if the cost difference between #4 and #6 is greater than $30.

 

[roadrunner255]

Thanks all for the comments.

Erector mentioned the second 12" design they do frequently.


Thanks

 

[carlaisle]

The instructions specify #6 rebar only for existing slabs. #4 is specified for new installations. The obvious explanation is they know no one has #6 rebar in their slab so, if you follow the instructions, you'll only install the lift onto new concrete that is (theoretically) built per their specifications.

 

[C-S-H]

The concrete slab is an essential part of the U-shaped moment frame of your 2-post lift. They gave you two reinforced concrete slab designs for your application. One is for a 4.25" slab, and the other is for a 12" slab. Your best design will fall between the two, but you will need to provide your own structural design. The AI answer above is garbage.

 

[wssix99]

The instructions specify #6 rebar only for existing slabs. #4 is specified for new installations. The obvious explanation is they know no one has #6 rebar in their slab so, if you follow the instructions, you'll only install the lift onto new concrete that is (theoretically) built per their specifications.

+1 We have seen this guide before. Some of the titling is confusing. It is NOT for the OP's situation. This guide is for existing concrete that needs to be cut out and have a new slab poured and tied into the old concrete.

For an entirely brand new slab, the specs are in the lift instructions. Just follow those and keep the control joints well clear of the posts (this will be the hardest part...) and everything should be good.

 

[caleb383]

Hello all,

12x40x48 post building moving along slowly.

Getting things together for a flooring quote. Slab will be non structural, and poured after the building is erected.

Plan on installing my bendpak 10k 2 post lift towards the center of the building.

Bendpak recommends a minimum thickness of 4.25 in. (108 mm) 3,000 PSI / 28 Day Aging and #6 Rebar (3/4"), and spacing of 12 in.

I was planning on using 6" of concrete, a contractor also suggested adding wire mesh as well.

Any comments?

Thanks!

Pouring a 6-inch concrete slab with rebar for a BendPak 10k 2-post lift is a smart approach. Exceeding the minimum requirements gives total peace of mind when hoisting heavy vehicles.

 

[finn]

Pouring a 6-inch concrete slab with rebar for a BendPak 10k 2-post lift is a smart approach. Exceeding the minimum requirements gives total peace of mind when hoisting heavy vehicles.

So you guys would design an airplane that would never fly, by that logic.

Engineering analysis always has a factor of safety in the calculations, and it’s not 1.001.

The credo typically espoused here on GJ. of make it bigger, is just dumb engineering applied by novices.

Reminds me of my brother in law, the English teacher, who mixed and poured a 12” slab for an outhouse at his cabin. The whole outhouse was about four feet square.

 

[wssix99]

If one wants piece of mind when lifting vehicles on a 2 post lift, I would look to making sure the load is balanced and proper jack stands are used vs over-designing the slab.