SR-71

I'm just finishing my new garage (30' x 40' pole construction, 10' walls, 15' roof height over each of the 4 bays), and I want to put in a lift. The floor is 4-6 inches thick (I didn't work real hard to make it totally even) 3500+ lbs fibre-reinforced concrete.

I searched the forums and found two threads on lifts. It's apparent that the majority prefer 2-post lifts, mostly for improved accessibility. But it's a narrow margin.

I not only need to lift my 'Bird, but also a Tahoe SUV, curb weight 5000 lbs. Also a mini-van (not mine, thank goodness) and a Ford Probe (go ahead and laugh, but it gets over 30 mpg).

I'm leaning toward a 4-post for safety (that is, how safe I "feel" lifting my baby with it, and working under it). I also may want to store a vehicle or boat overhead from time to time. I figure I can deal with the ground clearance putting the 'Bird on and off.

But I want to clarify a couple things before I buy.

How is a 2-post lift anchored? If I get a 2-post, do I have to drill holes in the floor and set in bolts? What keeps them from pulling out? Or does it have a base plate? Basically, what keeps it from tipping over with all that weight on it? What's holding the danged thing up?

Are there any 4-posts that can move the platforms closer/farther apart? Seems to me that if the width between platforms could be adjusted, that would solve a lot of accessibility problems, and maybe I could use the lift to work under my big Bob-Kat commercial mower, too.

Fyrstorm

iTrader: (1)

To me the 4-6" slab as a base I'd find concerning, if it were me I'd figure out where the legs of the lift were going to sit and give them each their own footing - like you'd do in a basement.

Having 5000lbs above my head, that is sitting on something thinner than your average sidewalk is kinda scary. I work in the constuction industry and even the floors in large stores (like Price Costco) are about 8". When I worked on a Speedy Muffler shop their floors were a foot thick -- but I'm not sure about how thick it was where the lifts were going. Airport aprons for unloading and loading passengers/cargo are 18-20" thick. All of these have reinforcing steel grids in them (10 to 15M if you know the gauges of steel, spaced in 4" squares).

Sorry though, I can't help you with how the lift is kept stationary.

Meant to add:

If you want to be absolutely sure about safety you can consult an engineering firm (even better if you know a civil engineer) and they can pop off a quick calculation for the point loads of what you want to lift and then compare it to the strength of your concrete. Maybe it's good enough, but what if there's settlement below the slab right where the foot were? Guess I'm paranoid but feeling safe is also a big concern as well hehe! And usually the safety factor is 3, so if what you are lifting needs a strength of 20mPa then the concrete should be 60mPa (sorry, canadian units...) - and be sure the ground where you are placing it is solid for sure as well. No good putting down a footing if the ground below it gives out.

BNBZ28

iTrader: (1)

when we built our garage we had a lift put in. we had it installed professionally (for safety reasons) they drilled 12 holes in the floor and put in some studs that will only go in one way kinda like an anchor they are probly 7/8 in diameter and they were torque to 150ft/lbs. i retorqued them about 3 months after it was in and havent had any problems. its a two post rated for 10,000 pounds. i think it was near 3k installed. i have lifted my moms infiniti qx56 which weighs around 5000 lbs give or take without any problems. and my dads company vans which are the dodge 2500, 3500s weighing near 8000 i would think. the 4 posts take alot of room and there really isnt a need for one unless you are buying an alignment rack.

BNBZ28

iTrader: (1)

just remembered they want you to have a minimum of 4inch think 3000psi fiber mesh concrete for that.

KWIK84

iTrader: (5)

The 2 post lifts are held in place by what are called "red-heads" think of basically a overgrown hollow wall anchor. I agree though 6" is a little thinner than I would like to use. The 4 posts are a great option though, with the load spread out over 4 points of contact your psi will be much less, and you can get these with a removable caster plate setup so that it can be moved around the shop (of course remove casters before putting a vehicle on the rack) as for an adjustable width, i have not seen one, not to say that a company doesn't make on just have never seen one.

SR-71

My floor is minimum 4" all over, up to 6" in places, and is 3500 psi fiber mesh. The 2-post lifts I've been looking at all specify what you said, 4" 3000 psi.

So I'm certain the floor can easily take a 4-post.

I'm not too sure about a 2-post that's basically bolted into the floor with anchors. I know the engineers have worked that all out, but stilll..... Kinda scary to me.

LAFireboyd

iTrader: (3)

I'll also be building a garage this spring, and I'm going with a 4-post lift. I prefer its versatility, its stability(even if that's only mental stability, lol) and that no special height requirements are necessary.

But there shouldn't be any worries about the concrete floor. If the minimum requirements are 4" thick @ 3000 psi, as xx11seczxx said, then you've more than covered that. Besides, think about it...

Our cars sit on only 4 points(a square foot each) on a basic concrete garage floor everyday. Distributing that 3500#, that's about 1100# per square foot on each of 2 points in the front and 700# per square foot on the rear points.

The only additional weight you'll be adding is the weight of the lift, itself, which is about 1500#. Distributing that between the 4 points and adding the car's weight to it, you'd be at about 5000#(the weight of those fancy SUVs that're already being supported safely on many garage floors--and you know those garage floors can support even larger vehicles than that). At the heaviest loads in front, you'd still only be at about 1500# per square foot.

Commercial requirements, naturally, would be more. There's much more at stake to the company and its insurance company if something failed. And you never know what else could end-up sitting on that floor, so it has to be built to withstand nearly any possible load.

My point is that we put A LOT of weight on our basic garage floors already, but we just don't realize it or think about it. Yet the floors are just fine.

So no worries, SR-71. It sounds like you're ready for your lift.

KWIK84

iTrader: (5)

No worries being under those lifts, spent 10 yrs under them at the dealerships. Technicians spend all day under them everyday. As long as you understand lifting points and weight distribution.

cooltc2004

iTrader: (4)

For a two post lift, you have to bolt it to the floor. That means bolts into your concrete. Im pretty sure its 6" thick minmum, but it could be 4". 2 post lift is nice for working on wheels (brakes, suspension, etc) where a 4 post is nice for everything else.

I have a 4 post lift. There is a good 2.5 - 3 feet between the ramps, and it could have been ordered with even more room in between the ramps. Whats nice, is that you can store a car on the lift, and actually move the lift around with the car still on it (obviously depending on your lift).

With my 4 post lift, I feel 100% safe underneith. If the hydrolics were to fail, there are stops on the side which catch the ramps. The MOST it could fall is 16 inches, but your not suppost to let the hydrolics support the weight, so that should never be the case.

/edit: LAFireboyd, there actually are height requirements. The 4 posts themselves are 7 feet tall, and if you want to go all the way up, add the height of your car (probably minus 1 foot). Take that into consideration.

There are some 2 post lifts that can lift 5+ tons safely. With a two post lift, once properly secured, won't go anywhere. Your garage could blow away before this thing would move. That should even be a worry.

LAFireboyd

iTrader: (3)

Sorry, I meant no height requirements for the building. A 2-post lift is tall, whereas a 4-post lift will fit into any residential garage. And yes, there's that added benefit of storing a car on the lift and parking another one underneath it.

PackmuleTA

concrete should be fine most places are 4-6 inches even house footers are usually that deep and they will hold alot more weight. you could get the concrete cut out where you are to place the plates at. drill rebar into the 4 sides and pour with a 4000- 5000 psi. That way the rebar will keep the new concrete from seperating from the old and while the concrete is wet get the bolts in to the correct position. I drive a concrete truck I've seen alot of ruff jobs but you should be fine with 3500 if you could find a way to get the bolts into the old concrete without them wanting to pull back out

Tranny

I've talked to several lift manufacturers and they are telling me 12" deep just around the base and then 4" every where else and 3000 psi rated concrete and the bolt anchors are epoxied in? I will hve them install it for safety.