Cement floor thickness for lift

[02chuck]

I am going to put in a two post lift(10,000#), but the floor of my shop was poured to be about 4 inches thick (per person that put it in). What I have read recommends 6-8 inches of cement. So I figure I need to cut out a square on each side to dig it down a bit deeper and reinforce it with rebar.
Looking for recommendations on size of square, thickness and any other things required.

Thanks
Chuck

 

[tff]

https://www.derekweaver.com/content... SPO10 & SPOA10 Installation Instructions.pdf

See page 5 of the rotary manual. Says 4’ x 4’ x 6” minimum. If you know which lift you’re getting I’d check their requirements as well.

 

[like2wheel]

You are going to get a lot of overboard suggestions from this form, but if your floors in good condition I would drill to check the thickness -because 4" in is adequate for some 10000 lb lifts. Many people go 5-6", but 8" seems ridiculous except in a corrective situation.

A quick Google on Bendpack's site:
XPR-10AS

10,000-lb. Capacity / Asymmetric Clearfloor

4" Min. Thickness / 3,000 psi



.

 

[02chuck]

Thank Guys
I had read the Bendpak minimums on the flooring thickness and had seen other information on thicknesses, but needed to hear other wisdom to make myself feel better. So I will cut the floor and do the 6 inch thickness. That way I feel better on the floor strength.

Thanks for the information.

Chuck

 

[R. Deschain]

I have a 10K Rotary. I have ~3700PSI concrte, 6" slab, fiber re-inforced, 8" welded wire, rebar in slab, and 4'x4'x12" footing with a rebar cage under each lift post. The footing was overkill, but... I like to way over build.

This guy has some sound advice as well:

 

[Retroman]

Just put in four footings for a performance shop for two lifts. The county required the footings to be 43"x 43" and a depth of 27" from top of slab with two mats of # 4 rebar at 12" ocew. These were bigger than we originally bid. I assume it has to do with the bearing pressure of the soil. Probably could have went smaller with a soils report, proctor and compaction test. We cut out a 6" slab to put these in.

 

[firebirdparts]

I am going to put in a two post lift(10,000#), but the floor of my shop was poured to be about 4 inches thick (per person that put it in). What I have read recommends 6-8 inches of cement. So I figure I need to cut out a square on each side to dig it down a bit deeper and reinforce it with rebar.
Looking for recommendations on size of square, thickness and any other things required.

Thanks
Chuck

The concrete doesn’t hold the lift up so much as it holds it down. So make the squares big enough that it goes all the way across and becomes on big rectangle. Make a concrete beam in the ground.

 

[wssix99]

So I will cut the floor and do the 6 inch thickness. That way I feel better on the floor strength.

This is an expensive thing to do for not having faith in the instructions. Bend-Pak has engineers who design these things and calculate the minimums. They have a lifetime of education, experience, and an installed base of equipment. You should feel confident in their specs.

Other manufacturers (like all other products) will have different specs because their products are designed differently and create different loads and stresses. (Even when lifting the same weight.)

For example, a lift with longer lift arms will create more "leverage" around the base when lifting a load - so that model may need deeper anchors.

Your Bend-Pak lift needs what it needs.

I had read the Bendpak minimums on the flooring thickness and had seen other information on thicknesses, but needed to hear other wisdom to make myself feel better.

The thickness of the concrete is required for embedment of the anchor bolts. (BTW - If you use the stock bolts in a 6" slab - you still get the same embedment as a 4" slab, so all that extra depth is a waste!)

The anchor bolts in the concrete develop a stress cone:

All the pull-out stresses in the bolts transfer their loads to the concrete on the surface area of these cones. That surface area (and the strength) roughly grows with the square of the depth. (If you want to pull Pi into the equation, you can get more precise numbers.)

Based on the tipping forces on the lift, that create pull-out forces on the bolts, which translate that force to the concrete, the need for depth is calculated. (Along with factors of safety.) (There are other aspects of the connections that are calculated, but this generally going to be the limiting one.)


As long as you have the depth in the concrete and use a good drill for a tight hole for the anchor, you are all great. If you have any further discomfort about the 2 post lift, I suggest purchasing proper tripod stands (also per the instructions.) Use of these stands will help make sure you don't overload the lift in the first place - and will never need to test those bolts pulling out:

 

[mcbane]

This is an expensive thing to do for not having faith in the instructions. Bend-Pak has engineers who design these things and calculate the minimums. They have a lifetime of education, experience, and an installed base of equipment. You should feel confident in their specs.

...

The thickness of the concrete is required for embedment of the anchor bolts. (BTW - If you use the stock bolts in a 6" slab - you still get the same embedment as a 4" slab, so all that extra depth is a waste!)

In the ideal case, look at the 12" slab Bend-pak recommends for new builds: https://www.bendpak.com/car-lifts/concrete-floor-requirements/. They allow 4-1/4" slabs for old work because if they required 5" they would lose sales to another company's sales engineer who says their lift can work on a thinner slab. There is an inherent conflict of interest for "sales engineers".

And if it was only about pullout forces, no lift manufacturer would specify rebar for lift installs. Flexural strength, punch shear capacity, and overall integrity of the slab are important too.

 

[Jking24]

I think people out think themselves in this forum. The difference between old slab and new has nothing to do with sales. When you cut your floor your compromising any strength it could provide theirfor the new slab must act as is own complete footing and provide the same strength and counter weight the uncompromised for would have. Don't over think it if they say 4-1/4" that's what you need end of discussion. And you can bet their is a large safety margin built into that recommendation. Don't over think. Or do and spend tons of money and time for absolutely no reason

 

[WNYflyer]

In the ideal case, look at the 12" slab Bend-pak recommends for new builds: https://www.bendpak.com/car-lifts/concrete-floor-requirements/. They allow 4-1/4" slabs for old work because if they required 5" they would lose sales to another company's sales engineer who says their lift can work on a thinner slab. There is an inherent conflict of interest for "sales engineers".

And if it was only about pullout forces, no lift manufacturer would specify rebar for lift installs. Flexural strength, punch shear capacity, and overall integrity of the slab are important too.

Most of the lifts I have looked into to seem to be very deliberate in holding back on the all the foundation requirements for say a two-post lift. They will say something simply like 4 1/2" slab with 4000 psi concrete then when you actually look at the installation manual they will mention such things as the minimum distance from edge of slab to anchor bolts, restrictions on control joint locations relative to the base plates, restrictions on cracks in existing concrete, etc. Up front most seem to limit the information on foundation requirements to that which the competitors show which I am sure as you said done for competitive reasons.

I have noticed that even Mohawk has now kind of hidden their foundation requirements such that you have to do a little digging. Again probably done for competitive reasons.

 

[recountryman]

You are going to get a lot of overboard suggestions from this form, but if your floors in good condition I would drill to check the thickness -because 4" in is adequate for some 10000 lb lifts. Many people go 5-6", but 8" seems ridiculous except in a corrective situation.

A quick Google on Bendpack's site:
XPR-10AS

10,000-lb. Capacity / Asymmetric Clearfloor

4" Min. Thickness / 3,000 psi



.

Just a FYI it's now 4.25" thickness /3000 psi. I just got a email from them where I asked if I get the area where the lift is going poured to 4.25" should it be 2 separate sections or just one pour covering both uprights. All they did was send the requirement sheet showing requirement of 4.25".

 

[jeffyhog]

Just a FYI it's now 4.25" thickness /3000 psi. I just got a email from them where I asked if I get the area where the lift is going poured to 4.25" should it be 2 separate sections or just one pour covering both uprights. All they did was send the requirement sheet showing requirement of 4.25".

Is this a new spec sheet from Bendpak? Everything I've ever seen said 4" thick and 3000psi. i just had a contractor out here yesterday to give me a bid on my new shop and i decided to verify my slab requirements. Here is the link to the bendpak PDF- https://www.bendpak.com/car-lifts/concrete-floor-requirements/

What's up with the requirement for #6 rebar? That's 3/4" rebar when I've never seen any call out for rebar. And the spec it at maximum 12" apart. my contractor says that 2 pieces of #6 rebar crossing each other is really too much for a 4.25" slab.

Where did these new specifications come from? Seems like overkill to me.

 

[wssix99]

In the ideal case, look at the 12" slab Bend-pak recommends for new builds

You should have stopped when you read this and it didn't make sense.

They allow 4-1/4" slabs for old work because if they required 5" they would lose sales to another company's sales engineer who says their lift can work on a thinner slab. There is an inherent conflict of interest for "sales engineers".

Making stuff up like this, which also doesn't make sense, makes you and your comment look even worse.

Read the page again. The 12" specs are for retrofit slabs installed into cut sections of sub-standard slabs. It's a "new" slab where the pre-existing slab doesn't meet spec - not new construction.

And if it was only about pullout forces, no lift manufacturer would specify rebar for lift installs. Flexural strength, punch shear capacity, and overall integrity of the slab are important too.

You should read my comment again. You didn't completely read that, either.

 

[wssix99]

BTW - Reading stuff on the internet (and for that matter making stuff up on the internet) should never be a substitute for reading the instructions. (carefully)

That being said - the Bend-Pak lift assembly instructions leave many things out. (Fortunately, the slab specs are good.) They have many addendums, corrections, and it's also not uncommon to have to call support to find out where to install the left-over hardware in the bag not illustrated on the paper.

 

[wssix99]

What's up with the requirement for #6 rebar? That's 3/4" rebar when I've never seen any call out for rebar.

Reading through the disclaimers they have added to the linked document on the page, it looks like they are concerned with people installing on cracked concrete. This spec is hefty and will stop cracking.

It's unfortunate that they gave the spec in #6. #4 is just fine. As long as the Steel Area Ratio is the same, then it can be converted for crack control. (#4 spaced 5.25" is equivalent to #6 every 12" in a 4.25" slab.)

And the spec it at maximum 12" apart. my contractor says that 2 pieces of #6 rebar crossing each other is really too much for a 4.25" slab.

For a regular slab where rebar is being used for crack control, this would be true for common practice of allowing for 1.5" to 2" of cover over the rebar.

This Bend-Pak rebar spec is exactly 2X what ACI specifies for crack control and exactly 1.5X what ACI specifies for control joint elimination. So, if one eliminates control (saw cut) joints, one should be able to go with less cover of the rebar. (Bend-Pak's instructions are assuming someone has already worked this out - they are not for new construction.)

If the slab goes over 4.25" thick, then ^ those safety margins drop with the lower Steel Area ratios in the cross section of the slab.

 

[ItsNemo]

You guys put a lot of faith in Bendpak but owning one of their lifts, I really question their competence.

 

[wssix99]

You guys put a lot of faith in Bendpak but owning one of their lifts, I really question their competence.

I have faith that their engineers won't kill me. I think the steel work is stout and I purchased mine for the dimensions and specific lifting specs, which are unique for my application.

The safety locks are not well thought out (on any model I own), the electrical hook-ups are wonky, and the shipping sucked. (I understand they are improving the later.) Is all that what you are talking about?

 

[mrobins297aaa]

why not just drill a hole thru your existing slab and see how thick it is?
before you start doing all this expensive extra work.

if you do cut your slab make sure you keep that rebar away from your anchor bolt locations because if you hit one when your drilling your anchor bolts you'll wish you never put that stuff in there.

 

[wssix99]

That way I feel better on the floor strength.

I expect that your instructions say nothing about rebar, (as mentioned in the supplement linked above) which is really about cracks and control joints. As long as you have the required thickness and have no cracks or control joints within the crack distance minimums given in the instructions, you should be clear and fine. Calling Bend-Pak should confirm that for you if you have any concerns.

 

[jeffyhog]

I expect that your instructions say nothing about rebar, (as mentioned in the supplement linked above) which is really about cracks and control joints. As long as you have the required thickness and have no cracks or control joints within the crack distance minimums given in the instructions, you should be clear and fine. Calling Bend-Pak should confirm that for you if you have any concerns.

I called Bendpak yesterday because i was confused about the differing information between my original owner's manual and the new 2019 concrete requirement data sheet. The person i spoke with would give me no other information other than telling me that they would email me a pdf of the current specifications. Really made me wonder if the original specs are being found to be insufficient. I would imagine there would be plenty of pictures online if slabs had failed under the load of the lifts.

I'm unsure what I should specify for my new building. I'm afraid that if I put all that #6 rebar every 12 inches in the area that the lift is going, I'll certainly hit some of them when I'm drilling for the anchor bolts. My original plans were for a 4.5" 3000psi slab with #4 rebar every 24" each way.

 

[wssix99]

I'm unsure what I should specify for my new building.

If you are building new, then you have some options. Personally, I think Bend-Pak's reinforcement recommendations are overkill for most people. (The reinforcement in my new garage was close because I was a little sketchy about the quality of the fill underneath.)

You can deviate from the #6 rebar as long as you keep the Steel Area ratio constant. You can go with #4 bar (and save a ton of money) and just space it closer so that the cross sectional ratio of steel to concrete remains constant.

^ ie: As the slab thickens, more steel is needed. You also technically need a little more steel when you jump up from 3000 psi concrete to 4000 psi concrete, but I think Bend-Pak's numbers and factors of safety account for people doing this...

I'm afraid that if I put all that #6 rebar every 12 inches in the area that the lift is going, I'll certainly hit some of them when I'm drilling for the anchor bolts.

Murphy's Law dictates that you will hit rebar in every single hole you drill! Even if you are spaced far apart, you'll hit one, for sure. Just get a proper rebar cutting bit (It will cost you $75.) and your life will be a breeze. You drill with the regular bit and then swap to the cutter when you hit the rebar and then end up with clean holes.

My original plans were for a 4.5" 3000psi slab with #4 rebar every 24" each way.

This is not enough steel to get you anything structurally. You would still need control joints every 10 feet and I think this is what Bend-Pak is trying to avoid now, with these specs. They (and all manufacturers) consider control joints "cracks" and can't be near the legs.

The other unfortunate thing about cracks and control joints is that when people forget them, the uncontrolled cracks form right in the middle of the room. (Right where the lift goes.) When people do remember them, they put them... right in the middle of the room - where the lift goes and where it clashes.

So, in order to do control joints properly and still accommodate a lift, we need to put in extra cuts, section the slab in thirds, and get enough rebar in there that we can push the distances past the standard 10'-12' common standard. (So there isn't a cut between the posts.) Bend-Pak's spec eliminates the need for these cuts and the need to worry about any of this.

 

[jeffyhog]

If you are building new, then you have some options. Personally, I think Bend-Pak's reinforcement recommendations are overkill for most people. (The reinforcement in my new garage was close because I was a little sketchy about the quality of the fill underneath.)

You can deviate from the #6 rebar as long as you keep the Steel Area ratio constant. You can go with #4 bar (and save a ton of money) and just space it closer so that the cross sectional ratio of steel to concrete remains constant.

^ ie: As the slab thickens, more steel is needed. You also technically need a little more steel when you jump up from 3000 psi concrete to 4000 psi concrete, but I think Bend-Pak's numbers and factors of safety account for people doing this...




Murphy's Law dictates that you will hit rebar in every single hole you drill! Even if you are spaced far apart, you'll hit one, for sure. Just get a proper rebar cutting bit (It will cost you $75.) and your life will be a breeze. You drill with the regular bit and then swap to the cutter when you hit the rebar and then end up with clean holes.




This is not enough steel to get you anything structurally. You would still need control joints every 10 feet and I think this is what Bend-Pak is trying to avoid now, with these specs. They (and all manufacturers) consider control joints "cracks" and can't be near the legs.

The other unfortunate thing about cracks and control joints is that when people forget them, the uncontrolled cracks form right in the middle of the room. (Right where the lift goes.) When people do remember them, they put them... right in the middle of the room - where the lift goes and where it clashes.

So, in order to do control joints properly and still accommodate a lift, we need to put in extra cuts, section the slab in thirds, and get enough rebar in there that we can push the distances past the standard 10'-12' common standard (So there isn't a cut between the posts.) Bend-Pak's spec eliminates the need for these cuts and the need to worry about any of this.

OK, thank you very much for the detailed explanation. I think I'm beginning to understand what the goal is, but I have no experience with concrete. I'm not sure I understand the steel area ratio. #6 rebar is 1.5x the thickness of #4, so does that mean I need 1.5x as much #4? I'm thinking it would be more because it's probably calculated by cross sectional area of the rebar.

Edit- I went back to your previous post where you said #4 rebar every 5.25" is equivalent to #6 every 12". Thank you for the information!

I hope I'm not hijacking this thread, but it all seems like information relevant to the OP's situation as well.

If I'm understanding correctly, the goal is to have no cracks (or saw cuts) between the lift posts which would compromise the rigidity of the slab and the lift structure. I was reluctant to specify thicker footings under the lift area as I was believing that the difference in concrete thickness would cause cracking around the thickened areas during curing. I guess that is a true statement, but the additional thicker rebar would prevent the cracking?

I was thinking that I would get the shop built, position the lift posts in place, and drive my biggest pickup between the posts and then decide where the final lift placement would be. I guess I need to figure out exactly where I want the lift to go and plan my excavation and rebar accordingly.

I'm putting in a MX-10AC lift. Its an older 10K pound model and measures 11' wide. If I understand the Bendpack slab requirements correctly, I need to dig a 4' by 13' by 12" deep area where the lift will be installed. The grid of #6 rebar will be at a depth of approximately 11", so they will be far too deep to hit while drilling. The rest of my slab could be 4.5 inches, but i would need to place #4x 18" minimum length rebar ever 18" around the perimeter as anchorage dowels. The concrete would need to be 4000psi.

Would it then be appropriate to specify the saw cuts to be made around the thicker 4x13' area and then every 10'? Or are you saying that I don't need to be concerned about cracking around or within that lift section because of the extra rebar? I'm guessing that I don't want cuts between the posts or within that 4x13 area.

How much rebar, and what size would you recommend under the rest of the slab? total size is 2000 square feet. i will also be installing a 4 post lift in another area, but i believe my original spec of 4.5" 3000 psi was just fine for a 12K pound 4 post lift.

 

[rburke65]

What ever the mfg. recommends. I went over board but that’s me. And I still use the tall tripods jack stands.

 

[wssix99]

I'm not sure I understand the steel area ratio. #6 rebar is 1.5x the thickness of #4, so does that mean I need 1.5x as much #4? I'm thinking it would be more because it's probably calculated by cross sectional area of the rebar.

Edit- I went back to your previous post where you said #4 rebar every 5.25" is equivalent to #6 every 12". Thank you for the information!

Yes, the calculation is the ratio of the cross section of the steel to the cross section of the concrete. (The area of the steel is the area of the circular cross section of the bar and then the area of the concrete is the depth of the slab times the rebar spacing.)

If I'm understanding correctly, the goal is to have no cracks (or saw cuts) between the lift posts which would compromise the rigidity of the slab and the lift structure.

The instructions should allow for cracks like this, even though these new Bend-Pak concrete specs do not. In theory... when concrete cracks; it will do so irregularly and the aggregate will interlock the cracked sections together. This may not always work as expected, so that may be why Bend-Pak is now recommending rebar - to cover things 100%.

IMO - If one has a cracked floor and those cracks are hairline and they are outside of the minimum distances listed, I would feel fine about things. For new construction, rebar is a great insurance policy to make sure cracks don't pop up where they can't be dealt with.

I was reluctant to specify thicker footings under the lift area as I was believing that the difference in concrete thickness would cause cracking around the thickened areas during curing.

Yes, right on.

I guess that is a true statement, but the additional thicker rebar would prevent the cracking?

Not necessarily. The regular design guides assume consistent reinforcement over a consistent cross section. To be in (full) control of changing cross sections, thicknesses, etc., special design and voodoo would required.

^ These lifts don't require "footings". The base plates have equivalent surface areas at the contact patches on a car's tires. So, there's no exceptional vertical stress on the concrete. The problematic forces are bending ones - this requires a flat, continuous, "plate" sitting on the ground to counteract.

I was thinking that I would get the shop built, position the lift posts in place, and drive my biggest pickup between the posts and then decide where the final lift placement would be. I guess I need to figure out exactly where I want the lift to go and plan my excavation and rebar accordingly.

No. If a brand new slab, it should be a consistent cross section and rebar needs to be consistent across the entire floor. If you have a bigger garage and don't want to reinforce the whole thing, separate the slab into sections with expansion joint and then reinforce only the section where you'll be putting the lift. (The expansion joint structurally isolates the sections.)

If I understand the Bendpack slab requirements correctly, I need to dig a 4' by 13' by 12" deep area where the lift will be installed.

This is only if you have an existing, substandard slab and need to cut out a section in the middle to retrofit it. All this depth and extra rebar is to address the undercutting of the original slab and to have the two parts work together as a bound unit. (single plate, all keyed in together) If your entire slab is new, you just pour it with the 4.25" spec. (This spec should not require saw cuts.)

 

[Beemer]

Cut out a piece and replace with what is needed. You can add rebar and easily make it like an independent footing in that area rather than just a slab, then you'll never worry about it.

 

[recountryman]

Is this a new spec sheet from Bendpak? Everything I've ever seen said 4" thick and 3000psi. i just had a contractor out here yesterday to give me a bid on my new shop and i decided to verify my slab requirements. Here is the link to the bendpak PDF- https://www.bendpak.com/car-lifts/concrete-floor-requirements/

What's up with the requirement for #6 rebar? That's 3/4" rebar when I've never seen any call out for rebar. And the spec it at maximum 12" apart. my contractor says that 2 pieces of #6 rebar crossing each other is really too much for a 4.25" slab.

Where did these new specifications come from? Seems like overkill to me.

Sorry forgot about this post. Anyway they specs your seeing for new floor is NOT for a new floor as in a new whole floor but one that section was cut out and re-poured due not to meeting the specs...see where it says

"New Concrete Slab Recommendations:

The information contained in this appendage supersedes any other information given in the accompanied manual. This information is presented for design recommendations for a new concrete slab in the event that the pre‐existing floor does not meet minimum requirements of the applicable lift type. Please read all instructions below carefully before producing new slab."

All needed for a new whole floor for lifts up to 10k per them is 4‐1/​4" thick @3000 PSI / 28 Day Aging and #6 Rebar

 

[Daedalus]

It always amazes me that people who pour 8" or 12" or 24" slabs for their lifts will not think twice about getting on an airplane or in an elevator without having to re-engineer them first too. People would rather pay more of their hard-earned money to bring peace of mind to avoid fear of an unknown bogeyman, than to trust the word of professionals who are educated, trained and licensed in exactly the things that these people don't understand.

 

[bad_idea]

My concern with 4" minimum thickness - is your slab actually 4" and does the lift manufacturer mean 4"? Typically a slab is formed up with 2x4s, which are actually 3 1/2" thick. How thick you figure the slab is?

 

[Daedalus]

My concern with 4" minimum thickness - is your slab actually 4" and does the lift manufacturer mean 4"? Typically a slab is formed up with 2x4s, which are actually 3 1/2" thick. How thick you figure the slab is?

I don't care if they use balsa stringers. When I'm paying for a 4" slab then that's what I want. When I had 20 yards poured a couple years ago you can bet I was out there with a laser level and a tape measure after the forms were laid. But that wasn't really the point of my post. Anyone pouring an 8" or thicker slab isn't trying to just meet a 4" min thickness.

 

[ocramidajzj]

@wssix99, so I know this is an old thread, but you appear to have some fact-based perspective. After over a year of research I haven't found an answer to the question of what margin of error in thickness across a floor would be consider safe. In my case I have drilled test holes and the measurements have ranged from 4.25, 3.5, 5 inches. And since the work-around to a substandard slab is to cut out/repour a 4x4 footing, should I then assume that I'm good as long as the depth is 4.25 within a 4x4 area? This is for installing a Max Jax. Appreciate any insights you can provide. Hopefully this thread isn't too old.

 

[wssix99]

I haven't found an answer to the question of what margin of error in thickness across a floor would be consider safe. In my case I have drilled test holes and the measurements have ranged from 4.25, 3.5, 5 inches. And since the work-around to a substandard slab is to cut out/repour a 4x4 footing, should I then assume that I'm good as long as the depth is 4.25 within a 4x4 area?

I think you are on to the right method. The area where you would want to be generally confident about the slab thickness would be over the lift's minimum footprint or minimum pad size. (Slight variations across the footprint are probably fine.) Often lift instructions will give this footprint as a special dimension in addition to the repair slab (where you cut out a section and replace it with a deeper section) specs.

The most important area for depth would be where you are placing the anchors. This is likely (lift design-wise) the more critical depth because it is needed in order for the anchors to achieve their full pull-out strength. Wikipedia has a good recent article that shows how this works: https://en.wikipedia.org/wiki/Concrete_cone_failure Concrete is weak in tension, so we need the anchors to get their proper depth to counteract that. The concrete resists pull-out along the surface area of a cone radiating from the bottom of the anchor. (see the wiki) As the anchor gets deeper, the concrete gets an exponential increase in pull-out resistance due to the geometry of that cone.

If you drill the holes for your anchors and don't have the depth, I would do the repair slabs. If you only have one or two holes that don't have the needed depth, you can call MaxJax to see what their tolerance is. Often, lift manufacturers have a factor of safety that can absorb one or two bolts that don't get their full depth.

 

[ocramidajzj]

Thank you so much @wssix99! Very much appreciated.

 

[cherokee]

I can only tell you what I did on mine. My building was all new, so I can't advise on the "dig a hole" type deal. The book for the lift I wanted said the same thing as quoted. I just had the entire thing done at 8", figured it is only going to hurt one thing.....the wallet. No harm in doing it all and only good can come from it.

A few years ago after I could do things again after my back surgery I went out to find a HUGE tunnel under my shop. Groundhog. OH GOD NO, was my first thought.

Everything was still fin inside, and I re packed gravel in there best I could.

Not saying having it that thick saved it from a bigger mess, but it sure did not hurt.

It was a huge den that sucker built, they are not little animals, and I never saw him, he was long gone.