Lift Pad Locations?

[VietGnome]

I'm currently in the trenches of planning my 30x40x12 stick build. I'm planning for 3'x3' reinforced pads in preparation for a lift down the road. I'm just trying to decide on a location.

The spots I have marked now have give me about 21' clearance from the main doors to the center of the pads. Meaning I should have plenty of clearance to park vehicle's and not worry about hitting the lift. The truck will just need to be parked on the man door side or be careful. This way I would also have the clearance for the 8x8 door to get 4 wheeler/tractor in and out, and have room to back my boat in that door and not hit the lift.

One consideration is in the fall I plan to back the duck boat into the garage still on the truck for ease of use in the mornings, so I'm unsure if I should shift the pads to the right slightly (i.e. center it off to the right door a bit ) so I'm not trying to weave the boat around the posts. Right now there's 3' from the inner wall to center of the pad.

 

[DAWrench]

I would shift the garage doors to the left so you are more lined up with the future lift placement.

 

[VietGnome]

I would shift the garage doors to the left so you are more lined up with the future lift placement.

That's fair. My original logic was keep them tight right so I have room for storage, a couple Freezers, etc along the left wall.

 

[kngelv]

I would also shift the doors left. if you are planning on leaving a boat attached and parking it in the same row as the lift then you should center the door on the lift pads so it's a straight shot. You really need to lay out the whole garage to figure out a lift location. With a gargae that deep I'd either put the lift at the front or back. I don't like anything large right in the middle.

James

 

[VietGnome]

I would also shift the doors left. if you are planning on leaving a boat attached and parking it in the same row as the lift then you should center the door on the lift pads so it's a straight shot. You really need to lay out the whole garage to figure out a lift location. With a gargae that deep I'd either put the lift at the front or back. I don't like anything large right in the middle.

James

I'm thinking about shifting the doors left slightly. The lift won't get a ton of use, so I figured the middle wouldn't block typical parking, and it would also keep the back free which is a planned shop area.

The boat's not big by any means, and it'll be getting stored parked sideways through the 8x8 door in the winter, so I dont want the lift blocking that. Summer itll probably be parked outside.

Parking it in there attached to the truck is just the solution to dry it out between hunts in the fall.

A slight shift in the doors will hopefully line things up better but still give me clearance on the left.

EDIT: the boat attached can get parked in either lane, doesn't have to be in the lift lane.

 

[wssix99]

I'm planning for 3'x3' reinforced pads in preparation for a lift down the road.

Don't do this. It's not required, it will make your pad weaker, encourage cracking and only lead to problems down the road. This type of thing is not in ANY lift manufacturer's instructions for a reason -> its a really bad idea. There are many threads on this, so I won't drain them here. (Unfortunately, the good information is mixed in with a lot of bad information so a careful read of the lift instructions will benefit you the most.)

New, simple concrete pads should be poured with a continuous cross section. Adding stuff like local reinforcement, penetrations, etc. induces cracking when the concrete cures and shrinks. 2 post lifts are designed to sit on unreinforced, simple slabs. 4 post lifts have even fewer requirements.

You may see instructions calling for local reinforcement for posts, but this is for retrofit slabs, where sections of old slabs need to be cut out and deeper repair sections added. Brand new slabs are different and have a separate section in the instructions.

The best thing you can do to plan ahead is to make sure you have proper thickness in the slab, have a control (saw cut) joint plan that says away from future post locations and have a plan to watch your contractor like a hawk while the pour is happening. (Giving them requirements for these things is not enough.)

 

[VietGnome]

Don't do this. It's not required, it will make your pad weaker, encourage cracking and only lead to problems down the road. This type of thing is not in ANY lift manufacturer's instructions for a reason -> its a really bad idea. There are many threads on this, so I won't drain them here. (Unfortunately, the good information is mixed in with a lot of bad information so a careful read of the lift instructions will benefit you the most.)

New, simple concrete pads should be poured with a continuous cross section. Adding stuff like local reinforcement, penetrations, etc. induces cracking when the concrete cures and shrinks. 2 post lifts are designed to sit on unreinforced, simple slabs. 4 post lifts have even fewer requirements.

You may see instructions calling for local reinforcement for posts, but this is for retrofit slabs, where sections of old slabs need to be cut out and deeper repair sections added. Brand new slabs are different and have a separate section in the instructions.

The best thing you can do to plan ahead is to make sure you have proper thickness in the slab, have a control (saw cut) joint plan that says away from future post locations and have a plan to watch your contractor like a hawk while the pour is happening. (Giving them requirements for these things is not enough.)

Very interesting. That's the first I've heard of this. Plan is for a 6" thick pad with 10M rebar.

Is there a rule or anything on how close a lift can be placed to a relief cut?

Anything else I should be watching for? Or just ensure they follow the plan?

 

[ericm]

I'd also line up the lift with the door that serves it. Either move the lift to the right or doors to the left or both.
Why are you putting the lift so far in from the door? Even a full size pickup (3/4 ton crew cab 6.8' bed) needs about 14' from the rear bumper to the center of gravity. My feeling is that every foot farther in than the end of the vehicle plus whatever clearance you want at the back when the garage door is closed is wasted space. You can't put stuff in that space or it will block access to the lift. But I want the lift free for relatively short term use by multiple vehicles. Some people put long term projects on them and that would call for different positioning.

I let my concrete guy talk me into 3'x3' pads. Worse, he did them with nice square edges, not tapered into the rest of the slab. As a result there's a crack in the slab around one of them. Look at the specs for the lifts you may want, pick the one with the requirement for the thickest slab, and make your whole slab that thick. If you really want thicker areas for the lift, maybe do it over a larger area and very gradually taper into it.

Most people think that there's a lot of downward force on the posts. But the foot on the bottom of each post is huge! The psi is lower than that of truck tires on the slab. The slab is really there to keep the posts from tilting.

 

[ericm]

Is there a rule or anything on how close a lift can be placed to a relief cut?

Yes. Read the install instructions for your lifts. For many of the 10k lifts I'm looking at it's 6" but sometimes it's different.

Make sure the concrete guy puts the cuts in the right places. I spent a morning with my guy to specify where the cuts go. I gave him a blueprint showing where not to make the cuts. I had to leave for home before he did the cuts. He did them slightly differently than we'd agreed on and did not check my diagram. One cut is close to where I wanted to put the lift, so I am going to have to move the lift 6" farther in.

In hindsight I should have put painters tape on the wall to show the no cut area.

 

[VietGnome]

-snip-

How far forward would you put it? I just dont want it so far forward that the posts would impede doors on vehicles, etc. The garage will see a lot more daily driving/parking than it will see vehicles on a lift if that makes sense.

I'll check the specs but I'm likely to inherit a 2post down the line.

Are your reinforced pads raised? Or you mean nice square edges on the bottom side and that caused the cracking?

Edit: a concern was also that farther forward i would risk hitting an open door, opening a door onto a car on the lift, or hitting the door opener.

 

[wssix99]

I let my concrete guy talk me into 3'x3' pads. Worse, he did them with nice square edges, not tapered into the rest of the slab. As a result there's a crack in the slab around one of them.

I'm sorry this happened to you. The edges of the square create a feature called a reentrant corner, which causes reentrant cracks. You will have them at each corner and may only be able to see them if you wet the slab. (They will not all open up to be the same width.)

At 3X3, the area will not meet the manufacturer's requirements for a 2 post lift. You will need to cut the floor and make a repair slab for a safe installation.

 

[ericm]

I'm sorry this happened to you. The edges of the square create a feature called a reentrant corner, which causes reentrant cracks. You will have them at each corner and may only be able to see them if you wet the slab. (They will not all open up to be the same width.)

At 3X3, the area will not meet the manufacturer's requirements for a 2 post lift. You will need to cut the floor and make a repair slab for a safe installation.

Even if the rest of the slab is thicker than the lift manufacturer's spec?

 

[wssix99]

Very interesting. That's the first I've heard of this. Plan is for a 6" thick pad with 10M rebar.

Did you see an authoritative reference that showed this as a good idea? You won't see any warnings not to do this because its wild-*** crazy from an engineering perspective. (So, engineers/designers will only put the acceptable options in the instructions.) Concrete finishers may come up with these kinds of ideas, but they do not typically have a design/engineering background.

I like putting rebar in the slab. It is NOT there for strength but crack control. (All concrete cracks.) It will help provide insurance that you will have an enjoy a quality slab for a long time.

No need to worry about this rebar. When you go to drill the lift, purchase a rebar cutting bit. (It is a great $100 investment.) If you hit rebar when drilling, switch to the cutting bit and its no sweat.

Is there a rule or anything on how close a lift can be placed to a relief cut?

This is in the lift instructions. Relief cuts (control joints) are treated just like a "crack." The concern is not with the concrete or strength, per se. These cuts and cracks need to be avoided for the bolting. The wedge bolts develop stress in the slab in the shape of a cone around the bolt. Cracks need to stay away from these stress areas. Lift manufacturers will give a distance, from the lift, to stay away from cracks so that the bolts are happy and so that there is also a margin of safety.

Anything else I should be watching for? Or just ensure they follow the plan?

Choosing your lift first helps and following the advice above to go with the most conservative requirements.

Thickness and control joints are the first thing to plan. If you are planning on hydronic heating, then routing those lines away from the post locations would also be a benefit.

 

[ericm]

How far forward would you put it? I just dont want it so far forward that the posts would impede doors on vehicles, etc. The garage will see a lot more daily driving/parking than it will see vehicles on a lift if that makes sense.

Yea if you're parking in the space ahead of the lift then you might want it a little forward. But 21' is longer than most cars. I guess it depends on how much space you want around the car when it's parked in that bay.

My goal is to keep the lift bay mostly free for cars that need a lift. But even if I want to park something there, most of my cars are significantly shorter than the 3/4 ton truck that the lift is spaced in to hold. The posts will be at the front fenders.

Are your reinforced pads raised? Or you mean nice square edges on the bottom side and that caused the cracking?

On the bottom side.

 

[wssix99]

Even if the rest of the slab is thicker than the lift manufacturer's spec?

Yes. a two post lift requires the slab to act like a flat plate in order to resist tipping:

The minimum size of a "pad" needed for a special installation is the manufacturer's repair slab size. (I have never seen one close to 3X3.) Even when a manufacturer provides specs for a repair slab, it needs to be pinned or keyed into the old slab so that the two still act as the "plate:"

A pad that isn't keyed into the slab like a full plate can just "tip out" of the hole!

 

[ericm]

A pad that isn't keyed into the slab like a full plate can just "tip out" of the hole!

I'm really hoping that you mis-understood me because my writing wasn't clear enough.

My slab was a single pour, not deeper pads poured later after cutting out sections of slab. The form was made deeper in two 3'x3' sections where the lift will be bolted down. There's a hair line crack along the outside of one of the pads.

If this is really a problem I'm going to have to have a lift installer look at it (expensive since the closest is 3 hours away) and if they agree it's a problem, negotiate with the concrete guy on fixing it. Or put my lift in a different bay.

 

[VietGnome]

Did you see an authoritative reference that showed this as a good idea? You won't see any warnings not to do this because its wild-*** crazy from an engineering perspective. (So, engineers/designers will only put the acceptable options in the instructions.) Concrete finishers may come up with these kinds of ideas, but they do not typically have a design/engineering background.

I like putting rebar in the slab. It is NOT there for strength but crack control. (All concrete cracks.) It will help provide insurance that you will have an enjoy a quality slab for a long time.

No need to worry about this rebar. When you go to drill the lift, purchase a rebar cutting bit. (It is a great $100 investment.) If you hit rebar when drilling, switch to the cutting bit and its no sweat.


This is in the lift instructions. Relief cuts (control joints) are treated just like a "crack." The concern is not with the concrete or strength, per se. These cuts and cracks need to be avoided for the bolting. The wedge bolts develop stress in the slab in the shape of a cone around the bolt. Cracks need to stay away from these stress areas. Lift manufacturers will give a distance, from the lift, to stay away from cracks so that the bolts are happy and so that there is also a margin of safety.


Choosing your lift first helps and following the advice above to go with the most conservative requirements.

Thickness and control joints are the first thing to plan. If you are planning on hydronic heating, then routing those lines away from the post locations would also be a benefit.

I sure haven't seen any references. Just internet speak, and it seemed logical in my head.

Regardless, I'll talk to the contractor when it's time and hash out joint locations.

In the mean time I think ill shift the doors left to center them up a bit more, and plan to set them around 16-17' from the doors.

I think that should give me enough clearance to not hit a door opener or open door with anything on the lift, but shouldn't impede opening doors when just parked.

Would you center both doors in the garage? Or just move them left slightly? i dont want to sacrifice too much space on the left hand wall, but don't think I want a lift closer than 36" to the wall.

Edit: now im thinking of keeping the doors but putting the lift in the left bay. I could still have the 5.5' clearance on the left side, easy for moving around the lift and working and id still keep clearance on that wall for Freezers/some storage

 

[carlaisle]

I would also line the lift up with one of the garage doors. What to move and how much you would be best suited to determine.

You don't need those extra footings/thickened areas for your lift. Check the specs from the lift manufacturer of your choice but, as a general rule, a 6" slab would be entirely adequate for most any passenger car lift. If you do the thickened areas anyway, make sure they are sloped about 45 degrees and not sharp right angles - those are the source of Eric's problems.

The location of the control cuts is important to the lift location. Include language in the contract with the concrete installer that specifies via diagram where they are to be located with a specific (and reasonable) margin of error. If he chooses not to follow instructions, he can tear it out and do it again at his expense. This is also a great way to weed out the concrete contractors you don't want to hire.

 

[wssix99]

If you do the thickened areas anyway, make sure they are sloped about 45 degrees and not sharp right angles

This is still a problem, although not as harsh as a straight-down shape. There is no technical specification, concrete finishing guide or other technique tested in science that indicates that this is acceptable in practice. (If there is, it would be interesting to read and I'd like to personally see it.) Any thickened area will still have an "anchoring" effect on the slab when it contracts during cure. Any reinforcing in the slab will have differential strain in the thickened areas. All of this increases the chances of uncontrolled cracking.

 

[wssix99]

I'm really hoping that you mis-understood me because my writing wasn't clear enough.

My slab was a single pour, not deeper pads poured later after cutting out sections of slab. The form was made deeper in two 3'x3' sections where the lift will be bolted down. There's a hair line crack along the outside of one of the pads.

When a concrete pad cures, it shrinks. Every edge of the slab (in an ideal world) physically moves towards the center when this happens. (In reality, the slab doesn't move freely across the ground and it will typically crack along the control joints and shrink inward within each saw-cut section.) The deeper section, in your case, creates a constraint (like an anchor) where the slab can't move. The rest of the slab pulls away from it and a crack forms.

Its not all gloom and doom and not like your crack is a clean cut. The crack is jagged and the two parts of the slab interlock somewhat, so the 3X3 block won't easily tip out, but that area is weaker than it would be otherwise with a solid slab.

If this is really a problem I'm going to have to have a lift installer look at it (expensive since the closest is 3 hours away) and if they agree it's a problem, negotiate with the concrete guy on fixing it. Or put my lift in a different bay.

Your installer and concrete guy won't have the technical expertise to evaluate this and when confronted with the fact that they didn't read instructions - I am 100% sure what they will say and tell you.

Instead, I would place a call to your lift manufacturer, insist you talk to technical support and give them the run-down of what has happened. As long as your cracks don't violate the post distance-to crack guideline, they may be able to bless your situation with certainty.

 

[AC-WC]

When a concrete pad cures, it shrinks. Every edge of the slab (in an ideal world) physically moves towards the center when this happens. (In reality, the slab doesn't move freely across the ground and it will typically crack along the control joints and shrink inward within each saw-cut section.) The deeper section, in your case, creates a constraint (like an anchor) where the slab can't move. The rest of the slab pulls away from it and a crack forms.

Its not all gloom and doom and not like your crack is a clean cut. The crack is jagged and the two parts of the slab interlock somewhat, so the 3X3 block won't easily tip out, but that area is weaker than it would be otherwise with a solid slab.


Your installer and concrete guy won't have the technical expertise to evaluate this and when confronted with the fact that they didn't read instructions - I am 100% sure what they will say and tell you.

Instead, I would place a call to your lift manufacturer, insist you talk to technical support and give them the run-down of what has happened. As long as your cracks don't violate the post distance-to crack guideline, they may be able to bless your situation with certainty.

I can add this-I spoke with my lift mfg and for mine they advised 4" thick. They did not specify anything else. Nothing about how far from cracks, psi, rebar, mesh etc. I was not comfortable with my floor due to numerous joints, age, spalling and unknown thickness. I did some research and found Bendpak's requirements. It is the only thing documented I could find from any manufacturer (probably a liability thing). I did follow their instructions almost to the letter. My only variation was using fiberglass rebar vs steel. Due to my situation mine was a retrofit.
You won't go wrong with their recommendations if you follow the lift capacity .

https://www.bendpak.com/media/wysiwyg/downloads/Concrete-Slab-Footer-Recommendations-BendPak-2025.pdf

Very few concrete guys know anything about lifts and I doubt anyone you find to do the work will either. Mine sure as heck didn't and I was glad I babysat the entire process. You've gotten good advise from the other posters.

 

[firebirdparts]

You can move the lift closer to the wall. People will tell you that you need a certain amount of space for actual work, but that's not really true. You can't actually get the vehicle close. You could get the post close enough that you don't want to walk around the post, but you can't really get a vehicle close to the wall using a 2 post lift. Just not possible.

I don't like the pads, but if you're just gonna shovel out a little more dirt for 6" then it'll be fine. Just make sure you don't have any neatness. Neatness leads to stress risers.

 

[dave*99]

 

[mikedodge]

You can move the lift closer to the wall. People will tell you that you need a certain amount of space for actual work, but that's not really true. You can't actually get the vehicle close. You could get the post close enough that you don't want to walk around the post, but you can't really get a vehicle close to the wall using a 2 post lift. Just not possible.

I don't like the pads, but if you're just gonna shovel out a little more dirt for 6" then it'll be fine. Just make sure you don't have any neatness. Neatness leads to stress risers.

There's usually a minimum dustsnce to stay away from the edge of the slab which is usyslly at the wall. I'd want enough space to get around the post because it's annoying when you can't do that and not being so close also gives you space to have a bench or to put things on that side such as the wheels when they come off and not be tripping over them.

 

[rust in the eye]

FWIW
My slab was poured with two 3' x 3' x 12" deep "pads" in the otherwise 5" slab to accomodate my lift posts, a monolithic pour, not cut into an existing slab. One pad is only a foot or so away from the edge. This was ~10 years ago and no cracks or problems at all.
I made these pads large for two reasons; possible small adjustment to planned post positions and mass.
My control post is 2' from a wall and I'm satisfied with the room to walk around there.
I'll suggest laying your plans out in full scale with tape on the floor and vertical obstacles where you'll place the posts, drive a car/truck onto your lift area then "work" around car. Lay some wheels down beside the car as you might while servicing, roll a tool box where you'd expect to use it and make some decisions in full scale. Sleep on the decided plan then do it again.

 

[finn]

You need at least two feet, and preferably three feet between the outside of the post and the wall.. More would be better if the pump and tank are mounted on that post.

5” of concrete is more than adequate. Mohawk has some crazy spec that’s far outside of anyone else. Makes one wonder what they’re smoking.

You can thicken the slab locally, per the description in the BendPak installation manual.

i suggest you select your lift first, then follow that manufacturer’s instructions as published in their installation manual.

Fiture proofing is an exercise in futility.

 

[dave*99]

I have 20” between my lift post and the wall. The pump is on that post. I can walk between the post and wall. No problem. I wouldn’t go less but I don’t need more.
There are no tool boxes or benches on that wall. Take your pick.

 

[jsaw]

You have to have enough space between the lift and the wall so that You have room to work . If You need to pull the axles out of a rear end to replace axle seals, You need room to move. If You are doing suspension work and need to have a 5 or 6 foot long prybar to pry down on a control arm, You need room to work.
If You need room to swing a sledge hammer, or use a slide hammer to remove a bearing, You need room to work. Too close to a wall, and Your lift is useless.

 

[gizardlizard]

Agree with the above post 100%. You always need more room than you think you do. I planned my lift location and AFTER I had the pads poured, I decided to shift things a little to gain more room. Best decision ever. I was worried the columns would make storage of other vehicles too tight. That should be secondary to the lift use. If you struggle when using the lift, what’s the point?

 

[Codyboy]

This is still a problem, although not as harsh as a straight-down shape. There is no technical specification, concrete finishing guide or other technique tested in science that indicates that this is acceptable in practice. (If there is, it would be interesting to read and I'd like to personally see it.) Any thickened area will still have an "anchoring" effect on the slab when it contracts during cure. Any reinforcing in the slab will have differential strain in the thickened areas. All of this increases the chances of uncontrolled cracking.

The slab for my house cracked.
Everywhere there was a dugout trench for a beam. The cracks run basically parallel to where the beams are located along the 4" part. The thick beam sections didnt Crack.
None of the cracks have ever opened up and are just hairline and at most a 1/16" or less.

 

[StefanNH]

Don't do this. It's not required, it will make your pad weaker, encourage cracking and only lead to problems down the road. This type of thing is not in ANY lift manufacturer's instructions for a reason -> its a really bad idea. There are many threads on this, so I won't drain them here. (Unfortunately, the good information is mixed in with a lot of bad information so a careful read of the lift instructions will benefit you the most.)

New, simple concrete pads should be poured with a continuous cross section. Adding stuff like local reinforcement, penetrations, etc. induces cracking when the concrete cures and shrinks. 2 post lifts are designed to sit on unreinforced, simple slabs. 4 post lifts have even fewer requirements.

You may see instructions calling for local reinforcement for posts, but this is for retrofit slabs, where sections of old slabs need to be cut out and deeper repair sections added. Brand new slabs are different and have a separate section in the instructions.

The best thing you can do to plan ahead is to make sure you have proper thickness in the slab, have a control (saw cut) joint plan that says away from future post locations and have a plan to watch your contractor like a hawk while the pour is happening. (Giving them requirements for these things is not enough.)

I am pouring a slab for my shop this spring. The concrete guy I am using recommended pouring deep where the posts go for added strength. This is the first I had heard of NOT reinforcing a section. Could you link some of the discussions on this?

 

[Codyboy]

I am pouring a slab for my shop this spring. The concrete guy I am using recommended pouring deep where the posts go for added strength. This is the first I had heard of NOT reinforcing a section. Could you link some of the discussions on this?

When I had the concrete poured for the shop I had a general idea but not specific where I'd put a lift.
I knew it would be somewhere in this 20x20 area. So that whole 20x20 got 6" of concrete.
He gently sloped down to that 6" depth from the adjacent 4" . Nothing harsh or squared edges on the transition but a very gentle slope.

 

[AC-WC]

I am pouring a slab for my shop this spring. The concrete guy I am using recommended pouring deep where the posts go for added strength. This is the first I had heard of NOT reinforcing a section. Could you link some of the discussions on this?

Stefan-please read the bendpak concrete requirements link above. On a new pour it is not required and there are several good points made in this entire post.
Adding a deeper section does not give you 'better' anchoring. Adding rebar/mesh along with stress cuts is the correct way to reinforce concrete.
A deeper section is recommended when you are doing a retrofit as recommended by bendpak.
No, I don't own a bendpak but do recognize good engineering recommendations.

 

[dave*99]

I am pouring a slab for my shop this spring. The concrete guy I am using recommended pouring deep where the posts go for added strength. This is the first I had heard of NOT reinforcing a section. Could you link some of the discussions on this?

I often find a large gap between what my owners manual says (post 23) and the advice on GJ. Be sure to have both handy as you plan your actions.
YMMV

 

[Codyboy]

Stefan-please read the bendpak concrete requirements link above. On a new pour it is not required and there are several good points made in this entire post.
Adding a deeper section does not give you 'better' anchoring. Adding rebar/mesh along with stress cuts is the correct way to reinforce concrete.
A deeper section is recommended when you are doing a retrofit as recommended by bendpak.
No, I don't own a bendpak but do recognize good engineering recommendations.

Maybe you or someone can answer this.
I have been looking at the bendpak 10AP.
I have looked at their requirements for concrete and 3000 psi and 4.25" thick is spec'd which i have covered with 3500 psi. and 5-6" thick.
They also state rebar has to be #4 (1/2") @ 12" o.c.
I only have 3/8" @ 16" o.c.
I verified this with my builder.

Is that a real issue?

Other lifts im looking at are the challenger versymmetric 10k
And a Weaver W pro 10.

I'll probably make my own thread to ask about those lifts but figured would try and clarify the bendpak issue since mentioned here already.

Thanks

 

[AC-WC]

I can't speak to the lifts, yes, I think we're hi-jacking this thread for that discussion so please start one for that. For the rebar-IF it's already down then I would contact bendpak or whichever mfg you decide and confirm with them. They may say it doesn't matter or they may say it needs the retrofit. It's so close to spec they may give you an OK to proceed.
If your concrete guy has already purchased the rebar convince him you must change to the 1/2" or fiberglass rod.
All you need is to show him the bendpak requirements and tell him it's direct from the engineer/manufacturer i.e. no different than an architect or building inspector.
Hope this helps!

 

[wssix99]

Maybe you or someone can answer this.
I have been looking at the bendpak 10AP.
I have looked at their requirements for concrete and 3000 psi and 4.25" thick is spec'd which i have covered with 3500 psi. and 5-6" thick.
They also state rebar has to be #4 (1/2") @ 12" o.c.
I only have 3/8" @ 16" o.c.
I verified this with my builder.

Is that a real issue?

No. The rebar is only there (in a new slab) for crack control. If your slab didn't crack after 30 days of cure, then you don't have a problem.

Rebar is not a requirement, it is just insurance against cracks forming outside the saw cut joints.

Bendpak's old instructions 10+ years ago called for 4" slabs with no reinforcing. These were the actual minimum requirements, but they left no room for mistakes or a fudge factor. (The bolts need that full 4".) The new BP specs are good practice and if you really dig deep in to the threads here, you'll find many people recommending rebar and going over 4" to give this room back in the day.

If you have any uncertainty, you can call BP customer service and they should provide you the same assurance. (We have had other threads with the same concern and they have confirmed the same for other members.)

 

[wssix99]

I am pouring a slab for my shop this spring. The concrete guy I am using recommended pouring deep where the posts go for added strength. This is the first I had heard of NOT reinforcing a section. Could you link some of the discussions on this?

I mean no disrespect, but I had to disprove every bad idea from a "professional" contractor or on this forum, my fingers would drop off.

I would approach this in a simple way:
1) Tell your contractor to follow the instructions that come with the lift. (If he gives you grief or disagrees, then tell him to "Follow the F'ing instructions that come with the lift.")
2) If he still gives you lip, then ask him where his engineering degree is from and what his grades were.
3) If he gives you a BS answer, ask him why he would give you advice that would violate ACI 360R-10.

If he still can't align to your lift manufacturer's expertise, then I would get another contractor ASAP as he might screw something else up on your house important.

If you are uncomfortable with the engineering and how a 2-post lift works safely with a simple slab, that's different. You can start another thread and we'd be happy to discuss it.

BTW - I have and regularly use one 2 post lift and two 4 posts lifts in my garage. The 2 post lift is hell and I deeply regret it. 4 posters are much better for casual use and aging bodies. ...and don't come with as many concrete, bolting or other complications.

 

[dave*99]

I mean no disrespect, but I had to disprove every bad idea from a "professional" contractor or on this forum, my fingers would drop off.

I would approach this in a simple way:
1) Tell your contractor to follow the instructions that come with the lift. (If he gives you grief or disagrees, then tell him to "Follow the F'ing instructions that come with the lift.")
2) If he still gives you lip, then ask him where his engineering degree is from and what his grades were.
3) If he gives you a BS answer, ask him why he would give you advice that would violate ACI 360R-10.

If he still can't align to your lift manufacturer's expertise, then I would get another contractor ASAP as he might screw something else up on your house important.

If you are uncomfortable with the engineering and how a 2-post lift works safely with a simple slab, that's different. You can start another thread and we'd be happy to discuss it.

BTW - I have and regularly use one 2 post lift and two 4 posts lifts in my garage. The 2 post lift is hell and I deeply regret it. 4 posters are much better for casual use and aging bodies. ...and don't come with as many concrete, bolting or other complications.

I agree with your statements to follow the lift manufacturers specs. I struggle to understand why there are so many independently arrived at solutions to this.

The lift manufacturers want to fit as many existing floors as reasonably possible.

 

[C-S-H]

Your 2-post lift needs a reinforced concrete structural slab. Your 3'x3' thickened areas will help with punching shear under the loaded edge of the post base plates, but otherwise are not the ideal shape of thickened slab that you need. The post is a cantilever with substantial moment applied to it, and that moment will to be taken to the slab. Then the slab will load the soil below it eccentrically to the center of the base plate. That is why you see the thickened slab spanning between posts, and extending out well past the base plate dimensions in the other directions. Your structural slab also needs to provide structural stability without relying on the minimally reinforced slab around it.

It is a simple structural slab design for a structural engineer. The punching shear on the loaded edge of the base plates determines the slab thickness. Then the rebar can be calculated using strength design by making the slab internal moment equal to the applied external moment. The anchor bolts have to be designed carefully as well.

Ex.:
External moment: 10000# / 2 posts * 1.25dynamic * 2 load factor * 36" arm length = 450,000 #-in per post
Internal moment: 0.9 strength reduction factor * 1.2 in^2(6-#4 rebar) * 60000psi steel rebar grade * 7.25" internal arm in 9" slab = 469,000#-in

So in this example I use 6 - #4 rebar in the bottom mat, both directions, within about a 3.5' design strip width under the base plates. And use half of that (3-#4) in the top mat at the base plates (both directions). So the primary steel is laid out in a giant capital I-shaped footprint. Use temperature and shrinkage steel rebar area beyond the design strip widths (top and bottom), and blend the 9" slab into the typical slab thickness. The softer the substrate, the wider the thickened slab area needs to be all around.