I bought a 14000 pond bend pak lift and alignment rack.(4 Post)
Question i see some 4 post lifts that are movable not bolted down. i rather not bolt this lift down if i don't have to. being a 4 post lift will it be self supporting?
I just finished the concrete in my shop its 5 inches thick with radiant heat and I'm afraid ill hit a line. any advice would be much apricated. thanks !!!

I think if you are going to use it as an alignment rack it would have to be flat and level. Anytime it is moved it should be leveled again. I once used a very expensive laser to level two Hunters that had been moved in an assembly plant. They had to be documented for ISO and MVSS compliance. You don't have to be that accurate. but it should be checked.

I would think you'd still want to not position the legs directly over a line anyhow, no? If you can be within a gap, I'd think that would be ideal. What's your line spacing?

I've read about guys using thermal cameras to see layout after the fact.

Portable lifts are designed for that. A bolted lift probably isn't. Also, check your spec sheet for the lift, 5 inches of concrete sounds marginal.

I put an Ammco 12000 4 post in my shop, it called for 6 inches and specified no cut lines within a distance of each post. I asked the concrete guys to wait a couple days before doing cuts so I could mark the appropriate areas as no cut zones.

There were similar restrictions for my 2 post lifts with the biggest difference the distance to cuts. Much larger area for the posts.

Note, I was doing a commercial installation and things got used daily. For a hobbyist you might get away with less but things only have to go wrong once.

I recommend rethinking your lift purchase and getting a portable one

I agree, I am looking at a portable 4 post lift, probably the backyard Buddy, if the lift is not portable it should be bolted in, too much risk otherwise. I think 6” is the minimal concrete recommended, I have 16” 4000 psi on the thin side and 36” on the other so I haven’t studied the concrete requirements too close, figured I have enough.

As to the stability, anchored or not, it depends on the lift. I have a friend with a Direct Lift PP9 Plus ((9,000 lb model) and he did not fasten it to the floor. BUT the installation manual says that anchoring to the floor is optional. This model also has a caster option so you can move it around. What does your installation manual call for?

My two post 10,000lb BendPak says 4" of 3000psi concrete is the requirement, and that's with only two pads touching the ground (most likely less surface area). I did pour closer to 6" in the area of the lift just to be sure. No issues after 15 years. I was definitely surprise when I read 4"

The lift needs to be designed to not be bolted down. If the instructions say to do it it needs it.
5" isn't enough for 2 post hoist, it might be for 4 since the load is less per point. The type of concrete matters too. I've seen hoists installed where the floor was thicker then that and they ended up cutting a square out under each post and re-pouring because the floor was cracking and coming apart with the weight and I'd imagine it would be more prone to that with radiant floor between the tubing and that's there and also the insulation that usually goes below it. If the floor was put in with normal parking in mind especially with radiant it usually can't handle the stress of having a hoist on it.

Ok, but how close to the cuts? Iirc my 2 post lifts wanted 4 foot squares to anchor to.

You will have to refer to the manufacturer's recommendations. Mine has instructions on how to install it on just about any surface including setting up outdoors on gravel.

Since I was wondering if my garage floor thickness was not adequate, would installing a
let's say 2' X 2' X 3/4" steel plate under the posts be a safe and cheaper alternative?

I would do a core sample or 4 for a basis.

Joe

that surely would spread the load, but i'm not an engineer so whether it would be adequate for say, a 3 1/2"-4" thick slab of concrete, that's way above my pay grade.
however, what about four jack stands holding up an entire car on a 3" slab ? they have four "tiny" 1 1/4-1 1/2" feet, 1/8" or so thick on a roughly 1 foot square area. those "feet" don't break the concrete, and i realize i'm not counting the weight of the lift, but i do kind of wonder.
wondering is probably what gets me in trouble most times.........

Moparx, the jack stand thing is something to think about.

Also, I have a drain in the middle of the area for the lift with slopes from side to side to accommodate
drainage. How do the lift instructions manage that?

Thanks,
Joe

PS along with the jack stand thinking, what about the load from the two little wheels of your floor jack lifting the front
of a C or B body, maybe 75% of the total car weight???

i believe it the jack wheels would also somewhat compare to the jack stands, with a very high pinpoint load on a very small contact patch of concrete.
but once again, i'm not an engineer, so i don't know how these examples would compare to the suggested support the lift legs require.
it still gives one something to think about.
a two post lift is an altogether different animal...........

thanks for all the replies. what I'm thinking about doing is putting in 2 5inch thick slabs of concrete over the top of my floor. thinking 2 ft in width the whole length of the lift on each side. mounting the lift on top kind of like the gas pumps islands at gas stations. I will pin the slabs in with some stainless steel doll pins ( drilling only a half inch so not to hit any water lines ) to keep it from moving and some ramp extensions for the difference in height my slab is probably more closer to 6 " thick and a 5 bag mix with fiber and wire mesh

Have the slab x-rayed to see where the lines are at?

Frankly I wouldn't go that route. You are still point loading the additional concrete footing and point loads tend to fracture concrete. When I had to install some additional support in my basement for the center stringer I faced a similar dilemma, point loads on a 3" thick concrete floor. What I ended up doing was using 12" X 12" X 1/2" steel plates. Worst case, that plate simply supported on the edges, should deflect about 0.020" with a point load of 5000 lbs. With my 3500 lb floor jacks I didn't think I'd have a problem and I haven't. So far.

As to hitting your embedded floor heat, use thermography to locate them. Works like a charm. A lot of building contractors now have thermography cameras to show homeowners where they have heat loss through windows, doors, etc. so I am confident you could round someone up to do that for you.

Maybe a cheap infrared thermometer? Like everyone used to check your temp last year. Cheap ones are about $15-$30 anywhere that sells tools.

A jackstand supporting a car 2 feet up is way different than a lift supporting a car 5 feet up.

It's not an issue of punching through the concrete but being able to hold the posts down while a car is in the air.

absolutely true for a two post lift, but a four post may be ok, stability wise ?