4" Concrete 2-post lift install thoughts?

[xjfish]

I want to install a 12k 2-post lift in my purchased home shop. Concrete is in generally good condition with no relief joints. I have no idea on PSI, although it is finished very smooth. I have about 6" of concrete at floor drain. At 20 years old, it has cracked, cracks are insignificant. Good packed gravel base that is dry and level. I drilled out concrete for a "test spot" and found to be 4.25" at crack. Edge of footings tells same. Amgo 12k hoist purchased has a 5" concrete requirement, with a 4-3/8" minimum embedment. I highly doubt I will be lifting vehicles over 10k, however, safety is utmost concern. Flame suit on.

Would you consider mounting lift to assumed 4" floor or have a deeper section poured in?

(Edited specs, were incorrect. 5" concrete requirement from 5.5 and 4-3/8" embedment from 3.5")

 

[gizardlizard]

I personally wouldn’t risk it. Had the same issue with mine. For my own piece of mind, I cut out two 4’ square pieces. Then dug down a foot and also under the existing slab to key in the new pours. Put rebar in (under old slab edges) and poured 12” of 4000 psi concrete. Paid under 400 bones for the concrete, 60 for rental on the walk behind concrete saw and the rest was my labor. Piece of mind on it is priceless. Again, just my opinion.

 

[Beemer]

Fully agree with the remark above.
I would cut out squares for new footings and at the same time establishing confidence that the concrete is on good subbase in the event that there is a bit of soil settlement under the existing slab. That way everything important is known and addressed at the same time.

 

[ducatithunder]

12K lol. If you dont plan on lifting more then 10K buy a 10K. 12K def seperates the men from the boys in regards to concrete spec. If your set on installing the 12K, dig it out and build it based on requirements for manufacturer. IIRC it was a 2x2 or 4x4 section and doweled in if the spec wasn't met. Chump change. Dont overkill it, just do what they ask. 10K from rotary asks for 4 inch with minimum embedment. I did 5 inch and there was a flux in the poor but it all above the minimum spec.

My fear is you send it, and regret it. The liability of someone AKA friend working in your shop and something goes sideways would be far worse than the original cost to do it right.

 

[Viper98912]

That's a big 2 post for unknown concrete (and potentially only 4"). Definitely cut out a couple squares and re-pour with what you know is right

 

[charbar]

I've done plenty of sketchy stuff but I don't think I could even talk myself into doing what you are proposing. Cut it out and repour thicker, don't be a statistic of stupidity. It might work fine, but do you really want to be second guessing it every single time you lift a vehicle up? Another inch of concrete doesn't seem like a lot but when you think of it as needing another 25% more concrete that puts it into a little better perspective. I wouldn't want to be wondering 'what if' every time I have a 9k pound pickup above my head.

The cost of cutting it out and repouring is going to be insignificant compared to if something does happen and at the MINIMUM you end up with f'd concrete, a trashed lift and a wrecked vehicle. Plus whatever else is in the way if it were to go over. Worse yet if it ends up killing someone......at best you're the only one that gets killed, imagine it goes over and kills your best friend, wife, child, etc and you have to live with knowing if you would have just bucked up and done it right in the first place everything would have been fine.

 

[southalabama]

Here lies xjfish. For want of a $750 fix he said hold my beer and gambled.

 

[wssix99]

Flame suit on.

lol I think you slept with your flame suit on last night!

Concrete is in generally good condition with no relief joints.

This is why your concrete is cracked. Guaranteed the cracks were there several weeks after it poured. ...Looking into my crystal ball, I see cracks radiating outwards from the floor drain that was installed.

^ This gives me some pause, here. A pro would not have installed a slab (particularly one with a drain/penetration in it) without saw cut joints.

The cracks are also your biggest worry for a 2 post lift. I would expect that your bolt holes are required to be at least 11" away from any cracks. (The concrete takes up the stress from the bolts in circular areas around the bolts. When the cracks intersect these areas, the strength of the system is reduced.)

Amgo 12k hoist purchased has a 5.5" concrete requirement, with a 3.5" minimum anchor depth.

If you are clear on the crack issue, you should call the manufacturer to confirm the situation. All have margins of safety that you can bite into but (as pointed out above) 12K lifts tend to have higher requirements.

with a 3.5" minimum anchor depth

This is surprising and another reason to call the manufacturer. (I'm so surprised, I would expect this is a typo. The spread between 3.5" and 5.5" is wide.)

If correct, then I would expect the concrete depth spec is off. The concrete below the anchor doesn't do anything structurally.

 

[ducatithunder]

The cracks are also your biggest worry for a 2 post lift. I would expect that your bolt holes are required to be at least 11" away from any cracks. (The concrete takes up the stress from the bolts in circular areas around the bolts. When the cracks intersect these areas, the strength of the system is reduced.)




If you are clear on the crack issue, you should call the manufacturer to confirm the situation. All have margins of safety that you can bite into but (as pointed out above) 12K lifts tend to have higher requirements.


This is surprising and another reason to call the manufacturer. (I'm so surprised, I would expect this is a typo. The spread between 3.5" and 5.5" is wide.)

If correct, then I would expect the concrete depth spec is off. The concrete below the anchor doesn't do anything structurally.

Rotarys spec is to have 6-1/4" from the edge of a bolt to any crack, joint, or edge for the hilti anchor bolts provided with their lifts. I dont have any relief cuts in my pour. Wasn't exactly sure where the lifts were going to go. I have a few shrinkage cracks I needed to work around to get the 6" buffer. The older rotary lifts had 5 bolts vs the 6 bolt pattern for the newer lifts for the exact reason stated above. Honestly wasn't worried about it as the lift straddles 2 large 16x16" grade beams with one 16x16" beam running down the center.

 

[Johnny chaos]

I foolishly read somewhere that 4" was the recommended thickness and had my floor poured to that thickness, then when the lift installer came he drilled a test hole and said he couldn't install my lift as the floor was only 4"........ oooops. I rented a saw and cut out the floor in two 4' square sections and went down 12" installed re bar and keyed under my existing concrete I did that myself; it only took one day and I feel much safer now. I would not recommend 4" after that whole fiasco. Other than having to cut into a brand new floor it wasn't bad or too expensive to do.

 

[xjfish]

lol I think you slept with your flame suit on last night!


This is why your concrete is cracked. Guaranteed the cracks were there several weeks after it poured. ...Looking into my crystal ball, I see cracks radiating outwards from the floor drain that was installed.

^ This gives me some pause, here. A pro would not have installed a slab (particularly one with a drain/penetration in it) without saw cut joints.

The cracks are also your biggest worry for a 2 post lift. I would expect that your bolt holes are required to be at least 11" away from any cracks. (The concrete takes up the stress from the bolts in circular areas around the bolts. When the cracks intersect these areas, the strength of the system is reduced.)




If you are clear on the crack issue, you should call the manufacturer to confirm the situation. All have margins of safety that you can bite into but (as pointed out above) 12K lifts tend to have higher requirements.


This is surprising and another reason to call the manufacturer. (I'm so surprised, I would expect this is a typo. The spread between 3.5" and 5.5" is wide.)

If correct, then I would expect the concrete depth spec is off. The concrete below the anchor doesn't do anything structurally.

I am well aware of reason why floor is cracked and understand conical anchor points. IDK why no relief joints, however, not uncommon from what I've seen around here. Your crystal ball is correct, biggest crack starts at floor drain. There are no cracks nearby where I purpose to install lift.

I edited first post. MFG requires 5" with 4+ imbedment. I may be almost there, however, floor is going to be 4" in spots, maybe thinner. I have read many related threads on this forum, several members have claimed 4" is plenty. Money is not a factor here. Time is somewhat.

I purchased 12k lift after going back and forth on a 10k... No regrets. Not surprised on floor thickness. I do believe best option is to cut out 4x4' sections and repour. Should I wait until the ground is above freezing?

I appreciate all replies. Happy New Year!

 

[wssix99]

Should I wait until the ground is above freezing?

Maybe not. Where are you located? Is your shop heated? If you have heat and foundation walls, the soil under your slab is probably not frozen, even if the soil outside is.

I edited first post. MFG requires 5" with 4+ imbedment. I may be almost there, however, floor is going to be 4" in spots, maybe thinner. I have read many related threads on this forum, several members have claimed 4" is plenty. Money is not a factor here. Time is somewhat.

This makes more sense. Embedment is everything and I'd suggest having a conversation with your lift manufacturer about it. I expect that the 5" is a guide for people to ensure they are working in a way that will guarantee that they can get the embedment.

If you need to pour a repair slab, you'll need 30 days of cure before you drill and install the lift.

I do believe best option is to cut out 4x4' sections and repour.

The lift manufacturer will have specifications for the repair slab, including required reinforcing. Some manufacturers allow for 2 sections. Others require a single pour with the entire area reinforced together. (On a two post lift, the slab acts as a beam between the posts, so this may be critical for the design. The manufacturer should have the required spec., keying details, etc.)

 

[NUTTSGT]

With no pictures, it's hard to actually say what to do as fixing the floor.

If you're cutting out two 4x4 sections, bring in a ready mix truck, break out your wallet. You're going to pay a small load charge but you might as well get your money's worth. Small load depends on concrete plant, it may be 3 yards, or it may be 5 yards. You'll have to call your local supplier.

Even at 12' thick, two 4x4 pads will take less than 1.25 yards.

A 6x12 pad, 12" thick comes in at 2.67 yards, closer to the minimum if 3 yards.

Use this site to figure how much concrete you'll need.

Concrete Calculator - How Much Do I Need? (Bags & Yards) - Concrete Network

Calculate how much concrete you need in cubic yards, meters or bags with our accurate, contractor-trusted concrete calculator. Easy to use on any device.

www.concretenetwork.com

Oh, add your rebar, it's cheap enough for 20' sticks at Menards.

 

[haveissues]

If you're cutting out two 4x4 sections, bring in a ready mix truck, break out your wallet. You're going to pay a small load charge but you might as well get your money's worth. Small load depends on concrete plant, it may be 3 yards, or it may be 5 yards. You'll have to call your local supplier.

We have a couple of onsite mix companies around here and I bet a lot of other places do also. They have a 2 yard minimum I think, perfect for this kind of stuff.

 

[xjfish]

Maybe not. Where are you located? Is your shop heated? If you have heat and foundation walls, the soil under your slab is probably not frozen, even if the soil outside is.


This makes more sense. Embedment is everything and I'd suggest having a conversation with your lift manufacturer about it. I expect that the 5" is a guide for people to ensure they are working in a way that will guarantee that they can get the embedment.

If you need to pour a repair slab, you'll need 30 days of cure before you drill and install the lift.


The lift manufacturer will have specifications for the repair slab, including required reinforcing. Some manufacturers allow for 2 sections. Others require a single pour with the entire area reinforced together. (On a two post lift, the slab acts as a beam between the posts, so this may be critical for the design. The manufacturer should have the required spec., keying details, etc.)

Located in MN. Shop is heated (40* min). Soil directly under slab not frozen. I guess I'd be concerned with longer cure time? I will do some additional research and contact lift manufacturer as you suggest.

NUTTSGT: I will attempt to update this thread with some pictures eventually. I appreciate your input. I may be looking to hire out the concrete job (home needs a slab/patio replaced eventually also), although I should probably consider DIY to get the ball rolling.

 

[wssix99]

Located in MN. Shop is heated (40* min). Soil directly under slab not frozen. I guess I'd be concerned with longer cure time?

Temperature affects cure time and strength but a heated garage is a fine temperature to cure concrete. You should still be fine after 28 days: https://www.concreteconstruction.ne... that,ultimately reaches the highest strength.

 

[xjfish]

Temperature affects cure time and strength but a heated garage is a fine temperature to cure concrete. You should still be fine after 28 days: https://www.concreteconstruction.net/how-to/best-curing-temperatures_o#:~:text=All of this suggests that,ultimately reaches the highest strength.

Thank you. A definite downside is cutting existing slab would potentially be a huge mess. Not opening doors and running fans outside in the winter. No running water in shop. Regardless, I am going to look into options.

 

[NUTTSGT]

We have a couple of onsite mix companies around here and I bet a lot of other places do also. They have a 2 yard minimum I think, perfect for this kind of stuff.

We don't have any of them around here, I wish we did. But you are right, perfect for a job like this.

However, we still don't know how bad the OP's concrete is. Would it hurt pouring/reporting a bigger section of the floor at this time ?

 

[NUTTSGT]

Thank you. A definite downside is cutting existing slab would potentially be a huge mess. Not opening doors and running fans outside in the winter. No running water in shop. Regardless, I am going to look into options.

It's going to be a mess.

Fans and doors open to keep dust at bay. If you're heating the garage, and have heat in the rest of the slab, it will recover faster than you think.

If need be, turn the heat up to 70 week prior to build up extra heat in the concrete floor. That is, if you are only removing a section for the lift.

 

[gizardlizard]

When I cut my floor, I used a walk behind wet saw, and a wet vac. Worked great and the dust was minimal. It’s all about water control and how much you are flooding the blade. Highly recommend a walk behind saw over a handheld that’s for sure.

 

[jonesg]

I'd wait for warmer weather in the spring, then you can run a hose .

 

[wssix99]

A definite downside is cutting existing slab would potentially be a huge mess.

You can get cutting companies to come out who would bring their own water. Downside is its an extra co$t.

 

[Natty Bumppo]

I had to cut my floor and pour new pads....the pad was thick enough but I had some cracks and some settling underneath and ended up with a void. Used a hand held saw...definitely a dirty job that I would not want to have to do again.

 

[xjfish]

We don't have any of them around here, I wish we did. But you are right, perfect for a job like this.

However, we still don't know how bad the OP's concrete is. Would it hurt pouring/reporting a bigger section of the floor at this time ?

I did a little checking around and it looks like everything local is larger quantity ready-mix. Possible to get adequate PSI with bagged concrete and rented mixer? OP's concrete is not "bad"; definitely not replacing more than what is needed to anchor lift safely.

It's going to be a mess.

Fans and doors open to keep dust at bay. If you're heating the garage, and have heat in the rest of the slab, it will recover faster than you think.

If need be, turn the heat up to 70 week prior to build up extra heat in the concrete floor. That is, if you are only removing a section for the lift.

Yeah. If I get time, maybe I will do all prep work and hire out pour?

When I cut my floor, I used a walk behind wet saw, and a wet vac. Worked great and the dust was minimal. It’s all about water control and how much you are flooding the blade. Highly recommend a walk behind saw over a handheld that’s for sure.

Stupid question: Can walk behind wet saws typically be used with a water tank or hose fed?

I'd wait for warmer weather in the spring, then you can run a hose .

I may not have much of a choice. To be honest, I have plenty of other projects to keep me busy until then.

You can get cutting companies to come out who would bring their own water. Downside is its an extra co$t.

Noted.

I had to cut my floor and pour new pads....the pad was thick enough but I had some cracks and some settling underneath and ended up with a void. Used a hand held saw...definitely a dirty job that I would not want to have to do again.

Looks good.

 

[NUTTSGT]

I personally wouldn't use bag mix to repair my floor for a lift pad. I even add extra Portland to my mix.

There's a discussion elsewhere about a concrete pad and lift setup.

I look at it this way, you are going to put a vehicle 6' over your head, do you really want to cheap out on what is holding that vehicle.

Bagged mix can be decent and can be inconsistent. I'll buy Sakerete or Quikrete but I will not buy Menards brand.

 

[gizardlizard]

I did a little checking around and it looks like everything local is larger quantity ready-mix. Possible to get adequate PSI with bagged concrete and rented mixer? OP's concrete is not "bad"; definitely not replacing more than what is needed to anchor lift safely.

Yeah. If I get time, maybe I will do all prep work and hire out pour?

Stupid question: Can walk behind wet saws typically be used with a water tank or hose fed?

I may not have much of a choice. To be honest, I have plenty of other projects to keep me busy until then.

Noted.

Looks good.

Walk behind saws require a hose hookup and water pressure is needed.

The directions that came with my Rotary lift specifically said NOT to use bag mix because of the inconsistencies.

 

[jonesg]

Walk behind saws require a hose hookup and water pressure is needed.

The directions that came with my Rotary lift specifically said NOT to use bag mix because of the inconsistencies.

bricklayers build houses by mixing mortar a bag at a time.
the problem, clearly seen on youtube, is the cowboys who don't measure water, they just use a hose .

When I ordered a few yards it arrived at least 45 minutes old, then another 30 minutes to pour and level , so you have some time to work with.

 

[mdim]

Although it would probably fine, I personally wouldn't risk it and would pour a couple footings where the lift will be. If nothing else there could be a liability issue if the floor isn't to spec and someone got hurt in an accident.

 

[xjfish]

I've been very busy lately. I'd like to get back to preparing for lift install. Prior to calling concrete guys or going nuts with a concrete saw, I did some more "test" drilling. Also, I changed location in shop where I plan to install lift. (Shop is roughly 48' deep by 34-35' wide with doors on narrow side) Now, plan is to install at rear bay with 12' door, lift will not be centered in 12' door, rather cheated closer to center of shop for working clearance. Previous plan was to install centered in 10' door side of shop in center between front and back walls. Too much overhead stuff to deal with and more cracks in concrete.

ANYWAYS: I have NEARLY 5" of concrete at this location and no cracks. Crude readings are AT LEAST 4.5" to 5" of good concrete. Measuring about 4.75+" consistently. Attaching a couple of pictures. The first pic with large crack was at 4-1/4" (where I initially checked) with maybe an open space underneath. Second pic hole and opposite holes have very good well packed base. It was impossible to measure without blowing out holes with compressed air.

SO: MFG requires 5" of 3500psi concrete and 4-3/8" anchor embedment for provided expansion anchors. I can easily attain minimum embedment with epoxy anchors, but a hair shy on depth. Unknown psi, see pics? I am highly leaning towards going this route now. This is just a home use lift. Currently I don't own anything over 7,000 lbs. Yes, I may eventually lift heavier stuff, with caution.

What say you garage journal experts?

EDIT: PICS NOT SHOWING. WORKING ON IT...

 

[xjfish]

Initial check. Largest crack in floor, roughly center of shop at rear.

 

[xjfish]

 

[Ponchohunter]

I had to cut my floor and pour new pads....the pad was thick enough but I had some cracks and some settling underneath and ended up with a void. Used a hand held saw...definitely a dirty job that I would not want to have to do again.

Very Nice! I'm getting ready to have a similar lift installed. I'm too old to be laying on the ground anymore! I have one of my four corners at entry of 25 year old + concrete pad that has a crack, nowhere near(like multiple feet from from where post feet will be). It has the thickness. It's actually a two part pad and it will be mounted on the pad with NO imperfections away from relief cut that separate the two. Will that possibly matter? Sorry, for jumping in on your post ,but still trying figure out how to post my question alone as I am a newbie to lifts and this site. Thanks and again, Nice setup! John

 

[mepstein]

Cut out the required amount, have the correct depth poured and never worry about it again.

 

[IndyGarage]

Do any of you guys have a calculator?

My 12K lift has footpads that are 18 by 24 inches. That's 432 square inches. If you put all the weight on one of the posts, it will have 12,000/432 or 27.8 PSI. With the weight evenly distributed it's half that.

I think a slab of wood can handle about 10X that easily.

If the concrete is stable and in good condition it won't have a problem with the lift. You'll put a ton more stress on the concrete when you are driving into the garage.

 

[Dig Doug]

Did you get your concrete done?

if you cut out pads make sure to dowel into the existing slab to tie the pad and slab together
and
I would add a mat at the bottom and chair it up 3 inch - 4 or 5 # 4 rebar each way

as for concrete
whitebag is $5.50 ea 5,000 psi
yellow is $4.50ea 4,000 psi

you could add a shovel of portland cement to each load (3 bags ) to make a better mix