Two post lift concrete mistake

[cccoltsicehockey]

Made the first large mistake in my build of the garage. Could be a costly one to correct.

New slab poured yesterday. It is 4.5in or 4000psi concrete with an extra area of 3.5ftx3.5ft that is 8in deep where the 2 post lift is supposed to go. It seems I forgot to tell the contractor those areas needed rebar. I unfortuantely only have wiremess in the entire slab now.

The plan is to install a BendPak 10APX lift. https://www.bendpak.com/10apx/ It does clearly state #6 rebar is needed. My mistake on this one. I should have sent the lift specs to the contractor so that nothing was missed.

A call to BendPak actually yielded unsuspecting answer though. The gentleman I spoke with said it should be fine although they still suggest rebar. So my question to those here, am I playing with fire by not cutting out a section of the brand new slab and having two pads poured to the BendPak existing concrete install specs with rebar?

 

[gizardlizard]

I just read the directions for your lift and only saw 3000 psi at 4 1/4” deep. Saw nothing about rebar needed.

 

[jack stand]

You will be fine, especially in a "hobby" situation. I'd think that most home lifts would be working hard if they saw 1 car a week on it.
You also heard it from them that rebar was a "suggestion", one that they'd be foolish not to give.

 

[sz0k30]

I have a 2 post lift on 4" concrete with no rebar or mesh only fiber strands. Has been standing for about 20 years.

So don't worry, you'll be fine.

 

[cccoltsicehockey]

I just read the directions for your lift and only saw 3000 psi at 4 1/4” deep. Saw nothing about rebar needed.

Sorry I forgot to also include this link. The main manual is what I originally had read about a year ago when planning this all. This document is much newer and at the time I had never seen. I wonder if it is some new CYA they have decided to go with. https://www.bendpak.com/media/wysiw...ommendations-BENDPAK-2023-Version2-Rev._B.pdf

You will be fine, especially in a "hobby" situation. I'd think that most home lifts would be working hard if they saw 1 car a week on it.
You also heard it from them that rebar was a "suggestion" that they'd be foolish not to give.

That is a good point. I likely will not be lifting aything more than 7000lbs on it although maybe if I have an EV someday they might weigh more.

They would be fullish not to give the suggestion for sure but how foolish is it to not follow it.

I have a 2 post lift on 4" concrete with no rebar or mesh only fiber strands. Has been standing for about 20 years.

So don't worry, you'll be fine.

That is good to hear.


Appreciate talking me off a ledge of ripping up part of a new slab.

 

[jetranger]

If I had extra depth, I'd take advantage and use 8" long all thread with epoxy. Now you're using the whole thickness instead of the mechanical anchors in the top half of the slap. I feel like that would make up for lack of rebar.

 

[575cat]

Another overthinker

 

[cccoltsicehockey]

Another overthinker

I will be there first to admit this is me 100% to a fault. I overthink and over engineer anything I do.

While keeping up with everything else on the project I let something slip but guess it seems I should be fine.

 

[jack stand]

Take a fraction of what you'd spend rebuilding your slab and buy some nice lift height jack stands and wrench on without this monkey on your back.

 

[Dig Doug]

Epoxy in all thread ! Drill down 7 inch - don’t blow thru the bottom of the concrete.

 

[cccoltsicehockey]

If I had extra depth, I'd take advantage and use 8" long all thread with epoxy. Now you're using the whole thickness instead of the mechanical anchors in the top half of the slap. I feel like that would make up for lack of rebar.

Had to actually look these up as I didn't full understand the process. This doesn't sound like a bad idea at all. Need to look more into them and make sure also the installed is familiar with them.

 

[jack stand]

Epoxy in all thread ! Drill down 7 inch - don’t blow thru the bottom of the concrete.

This makes a lot of sense to me.

 

[Dig Doug]

Do some research

Epoxy Anchoring Adhesives

<p>Epoxy-based anchoring adhesives are designed for anchoring threaded rod, rebar and smooth dowels in a variety of base materials. These products provide strength and versatility across a wide variety of applications and are excellent for use in cold weather conditions or applications where...

www.strongtie.com

follow the instructions - prep everything prior to tapping the epoxy tube!
side note - here in Ca, there are times when a special inspector is required to monitor the application of the process

so watch a U tube & read the instructions !

This is the most important part of using epoxy, the 2nd is making sure it’s mixed in the mixing nozzle correctly should all be a uniform color third is hole size for the correct all thread size

drill the hole clean and brush ( use a vacuum or air compressor to blow out ) the hole. No dust inside the drilled hole it will weaken the bond

 

[arrowhead]

Take a fraction of what you'd spend rebuilding your slab and buy some nice lift height jack stands and wrench on without this monkey on your back.

I got 4 of these. Not so much because I don't trust the concrete or the lift, but they really help stabilize things from moving around. The extra security is just a bonus. https://www.harborfreight.com/autom...n-capacity-underhoist-safety-stand-61600.html

 

[Hubmonkey]

Yeah I just had a 2post 10k lift installed and was worried about all the things I have heard about horror stories of lift installs... My Situation is 5" 3500 PSI Concrete with mesh and I have been put at ease by the Lift Manufacturer's engineers and the installer on several separate conversations. You are fine just get it installed and enjoy.

 

[cccoltsicehockey]

Yeah I just had a 2post 10k lift installed and was worried about all the things I have heard about horror stories of lift installs... My Situation is 5" 3500 PSI Concrete with mesh and I have been put at ease by the Lift Manufacturer's engineers and the installer on several separate conversations. You are fine just get it installed and enjoy.

Appreciate this personal experience. Between this, some epoxy bolts, and an extra jack lift stand so I have one for both ends (already planned on one anyways) I feel a lot better about not worrying about things.

 

[ConCretin]

I think you may be confusing Benpack's specs for a retrofit repair with new construction. I seem to recall a repair detail for a deficient existing slab that called out #6 bars but that wouldn't ever be applicable to a new slab. Not to second guess professionals but the idea of putting 3/4" rebar in a slab on grade is absurd. Based on your description, you are absolutely fine. Carry on and enjoy your new shop and lift.

 

[Garrym]

Both of my 2 post lifts have the posts tied to the roof structure with brackets I made.
One has only 80mm concrete, the other about 100.
The bolts into the concrete only have to stop the base of the post from moving.
Both lifts are solid as rock.

 

[CraigStu]

I would get the all thread from McMaster Carr. They have a huge variety w/ great explanations of the qualities of various alloys. I'd be leery of all thread from L or HD.

 

[larry4406]

A competent lumber yard can order Simpson brand anchor rods in various diameters and lengths.

We get 3’ long rods that are 1” diameter for some of our house types. Simpson also has the epoxy, nuts, washers, etc.

 

[George-in-NH]

I have a 2 post 9k lift in 5" of concrete with no rebar or wire, only fiber mesh in mix - due to a miscommunication during floor installation. If concrete was good quality don't worry about it.

 

[70runner]

If you go the epoxy route, which I recommend, take a look at the Hilti HY200 adhesive system with their HIT-Z anchors. This is the system they recommended to me for my 2 post lift. This system does not require hole cleanup though I still did that. My pad is 5" 3500psi, with a 4'x12', 12" deep tray centered on the lift posts. I used the 3/4" HIT-Z, 9 3/4" long.

 

[wssix99]

I think you may be confusing Benpack's specs for a retrofit repair with new construction. I seem to recall a repair detail for a deficient existing slab that called out #6 bars but that wouldn't ever be applicable to a new slab. Not to second guess professionals but the idea of putting 3/4" rebar in a slab on grade is absurd. Based on your description, you are absolutely fine. Carry on and enjoy your new shop and lift.

Bendpak is now publishing a new concrete guide that specifies wire mesh or rebar (for crack control) of various sizes, depending on the slab thickness and lift model being used.

...In true Bendpak fashion, the specs in the concrete guide don't match the specs in the lift instructions.

(Full disclosure - I love my Bendpak lifts. The accuracy of the instructions - for all of them - have continually left things to be desired.)

 

[wssix99]

A call to BendPak actually yielded unsuspecting answer though. The gentleman I spoke with said it should be fine although they still suggest rebar.

The rebar they were suggesting was for (shrinkage) crack control for new construction slabs. It is not an absolute requirement and just helps control cracking. If you have proper saw cut joints, that's the most important thing.

It sounds like you are generally in-line with the installation manual specs, which are the legacy instructions and have been working fine for properly placed slabs. All of the new stuff in the new concrete guide looks to be there as additional insurance policies.

with an extra area of 3.5ftx3.5ft that is 8in deep where the 2 post lift is supposed to go. It seems I forgot to tell the contractor those areas needed rebar.

This is the only thing that gives me pause. The instructions call for a slab of a continuous cross section. Having these deeper areas can cause cracking, although you will see posts from many members here who have done this without any adverse effects. (Doing this in the middle of the slab, where a lift would can be less stressful.)

^ Placing limited rebar in these areas would have been problematic, so its good that its not there. This is only done for repair slabs.


If you wait your 28 days for the slab to cure and don't have any cracking within the limits in the instructions, you should be all good!

 

[Homewrecker]

If you go the epoxy route, which I recommend, take a look at the Hilti HY200 adhesive system with their HIT-Z anchors. This is the system they recommended to me for my 2 post lift. This system does not require hole cleanup though I still did that. My pad is 5" 3500psi, with a 4'x12', 12" deep tray centered on the lift posts. I used the 3/4" HIT-Z, 9 3/4" long.

Did you install these initially or switch over to them from previously installed wedge anchors? I have wedge anchors right now and was thinking of replacing them with these since some of my existing anchors keep taking torque during monthly re-torques.

 

[cccoltsicehockey]

Bendpak is now publishing a new concrete guide that specifies wire mesh or rebar (for crack control) of various sizes, depending on the slab thickness and lift model being used.

...In true Bendpak fashion, the specs in the concrete guide don't match the specs in the lift instructions.

(Full disclosure - I love my Bendpak lifts. The accuracy of the instructions - for all of them - have continually left things to be desired.)

This is the biggest issue you have pointed out. They consistently seem to change their separate concrete instructions and never update the rest of their documents.

 

[cccoltsicehockey]

If you go the epoxy route, which I recommend, take a look at the Hilti HY200 adhesive system with their HIT-Z anchors. This is the system they recommended to me for my 2 post lift. This system does not require hole cleanup though I still did that. My pad is 5" 3500psi, with a 4'x12', 12" deep tray centered on the lift posts. I used the 3/4" HIT-Z, 9 3/4" long.

Wow these look great. Will look into these.

 

[cccoltsicehockey]

I have a new cause for concern. I had them run conduit to up right next to one of the lift posts so I did not have to do the power above ground. Where the conduit comes up inside of one of the walls it is nice an solid in the concrete. However, where it comes up next to the lift post the concrete has already pulled away from the conduit. This has me concerned that there is an open pocket on the underside of the slab around the conduit. Waiting to speak with my builder about this but I can't say it gives me warm fuzzies thinking there might be a pocked under the surface so close to where the bolts will go into the slab. If what I am saying isn't clear I will grab some pictures later today.

 

[Rusted Nut]

I have wedge anchors right now and was thinking of replacing them with these since some of my existing anchors keep taking torque during monthly re-torques.

if you have to re-torque monthly, those anchors are pulling out and are no where near as strong as they should be. Hilti epoxy products are excellent!

 

[finn]

I would get the all thread from McMaster Carr. They have a huge variety w/ great explanations of the qualities of various alloys. I'd be leery of all thread from L or HD.

This!

When I hear people saying to use all thread, my mind immediately conjures pictures of people going to HD or Ace and getting the cheap grade 2 imported junk on the rack.

I used epoxy on a couple holes that didn’t seem right with my drop in anchors. I used Simpson (I think) high strength threaded rod designed for this application. Pretty sure it was grade 8.

 

[C-S-H]

I seem to recall a repair detail for a deficient existing slab that called out #6 bars but that wouldn't ever be applicable to a new slab. Not to second guess professionals but the idea of putting 3/4" rebar in a slab on grade is absurd.

Yes, absurd. Reviewing their documents and details, they demonstrate no understanding of reinforced concrete.

 

[C-S-H]

The rebar they were suggesting was for (shrinkage) crack control for new construction slabs. It is not an absolute requirement and just helps control cracking. If you have proper saw cut joints, that's the most important thing.

The presence of the lift makes this a structural slab, and therefore requires temperature and shrinkage reinforcement at the minimum.

This is the only thing that gives me pause. The instructions call for a slab of a continuous cross section. Having these deeper areas can cause cracking, although you will see posts from many members here who have done this without any adverse effects. (Doing this in the middle of the slab, where a lift would can be less stressful.)

This is not an inherent problem. We cast concrete in all kinds of configurations without any cracking. All you need is good mix design, good batching, good concreting, and good curing. Same as last 2000 years.

Placing limited rebar in these areas would have been problematic, so its good that its not there. This is only done for repair slabs.

We make castings with radically different amounts of rebar in various portions of the casting. No cracking if done as per above.

 

[Scotto]

I got 4 of these. Not so much because I don't trust the concrete or the lift, but they really help stabilize things from moving around. The extra security is just a bonus. https://www.harborfreight.com/autom...n-capacity-underhoist-safety-stand-61600.html

I have one as well and love it. I've been lazy admittingly in using it all the time but it sure firms everything up when you put it under the rear end.

 

[finn]

I have one as well and love it. I've been lazy admittingly in using it all the time but it sure firms everything up when you put it under the rear end.

My observations are that there are more incidences of cars falling off of lifts, if internet pictures are anywhere near accurate, than incidences of lifts themselves failing. Despite that, here on GJ, the preponderance of discussions are around who builds the biggest, baddest lift.

The underlift support devices just aren’t as impressive, I guess, since they’re relatively inexpensive.

I’ve been using an OTC four leg support and a single post Sunex (?) support. The single post takes up less space, but I plan on buying another four leg since they’re so much more stable. I can’t say I use the stabilizer 100% of the time, but it’s pretty close, especially when there’s something long up in the air.

 

[Zeke]

I can't imagine not cleaning a drilled hole in concrete whether they say it's not needed or needed. (Post #22)

AFA the concrete separating from the conduit, just tap the surface with a hammer and listen. Do this in various places and you will learn quickly what solid concrete sounds like.

Why don't people put in Sonotube type piers in new floors when they know they are installing a lift? Everyone seems to have questions about this. I don't want any questions if it's my job.

 

[Rusted Nut]

I can't imagine not cleaning a drilled hole in concrete whether they say it's not needed or needed. (Post #22)

If there is dust in an epoxy hole, the epoxy won't bind to the wall as well as designed, and you will severely reduce your design strength. Inspectors will check minimum hole diameter, and put a large q-tip in the hole to check for dust. If it's not clean, they won't let you install.

 

[wssix99]

The presence of the lift makes this a structural slab, and therefore requires temperature and shrinkage reinforcement at the minimum.

This is not an inherent problem. We cast concrete in all kinds of configurations without any cracking. All you need is good mix design, good batching, good concreting, and good curing. Same as last 2000 years.

We make castings with radically different amounts of rebar in various portions of the casting. No cracking if done as per above.

The practices that apply to a slab on grade are different than for elevated structures, beams, columns, etc. The reinforcing on a continuously supported slab is completely different than other simply supported concrete. The American Concrete Institute and other like bodies have special guides for this type of construction.

Slabs on grade also have a unique issue where they experience tension across their entire area due to shrinkage. These forces are concentrated in the middle of the slab and complicated by penetrations, features like reentrant corners, and inconsistencies in the cross section. (If not accounted for by proper isolation and control joint design, uncontrolled cracking occurs.)

 

[msharley]

Appreciate this personal experience. Between this, some epoxy bolts, and an extra jack lift stand so I have one for both ends (already planned on one anyways) I feel a lot better about not worrying about things.

The HILTI brand Epoxy Anchors are super simple to use....

Have put in hundreds of them over the years.

Simply wrap a piece of tape around the bit (the depth stop always seems to be in the way or ......comes loose in mid hole) drill, blow out the dust...epoxy & anchor. .... used to be a 24hr cure time?


And of course it is easier with a HILTI gun & bit....no re bar makes the drilling easier.

 

[Beemer]

A call to BendPak actually yielded unsuspecting answer though. The gentleman I spoke with said it should be fine although they still suggest rebar. So my question to those here, am I playing with fire by not cutting out a section of the brand new slab and having two pads poured to the BendPak existing concrete install specs with rebar?

Don't you just love contradictory answers from the same entity?
That being said, an Engineer could check the unreinforced concrete if he had access to the loading data.
It might be less expensive to replace the pads though but it would be nice to not have have those new joints showing where settlement might occur.

 

[haveissues]

The fact that other companies such as rotary don't specify rebar combined with bendpak also specifies 3/4" rebar under a frikin 6k movable scissor lift in that document makes me think someone f'ed up when making it. I would attach it to the concrete you ave and not loose any sleep.