Heavy forklift load on warehouse floor
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  1. #1
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    Default Heavy forklift load on warehouse floor

    Just bought a used Cat forklift weighing something over 14k lbs. I’d like to run it all around the warehouse whenever I want. Landlord’s statement on limit of floor loading is “2000 psf.” Is there any data available on floor loading by forklifts? I’m guessing the landlord’s figure applies to static loading, so how would that relate to dynamic loading by a rolling forklift? Another guess is that there’s a big difference in floor loading by balloon tires vs. solid tires. Then of course the empty weight of that forklift isn’t the worst case. Lifting capacity is 10k lbs. so worst case is loaded forklift at 24,000 lbs. The floor is fortunately on the ground and has been that way for at least a decade, probably concrete over gravel over dirt, in a well-drained area, no soft ground I’m aware of. I’ve already driven a forklift weighing 8k lbs all around this floor with various loads. It has solid tires. Floor shows no damage from this lighter machine.

    You can understand my issue, I’d like to know the chances that my loaded forklift will seriously damage the floor. There are already a few cracks in it but those are hairline and both sides of crack are at same level.

    35798151-dc1f-4195-b259-6bf2ba5049af.jpg

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    So the forklift is 8 feet long, 4 feet wide.. Even fully loaded at 24k thats
    less than 1000lbs per sqrft.

    That's your argument.. Stick to that..

    Say you weigh 200 lbs and are walking across the floor and the only thing that is hitting the floor is your
    heel.. Maybe 2 square inches... That's 100 lbs per inch, 14,000 plus per sqrft. OR!!! you could say you
    only put down 200 lbs in that sqrft, so you were well within the limit.

    If you do crack the floor (you won't) slather some bondo in there and paint it before you leave.
    Probably some boiler plate BS that doesn't mean anything anyways.

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    Ok thanks, now on a related question a friend wants to sell me an old monstrous 28 x 280 lathe that’s about 20 ft long and weighs about 10 tons. I’ll have to have professional riggers move it of course. Sound like a problem for the 2000 psf-rated floor or not? Offhand I don’t know how many feet it has nor their dimensions.

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    You could have some fun with this.

    If you crack the floor get the landlord by to stand on the crack. One foot only and even then just on his toes.


    Do the math, 2K lbs per square foot equals 14 lbs (rounding) per square inch. So if a weigh 200lbs (yeah right 200lbs) and I stand on my toes on one foot then all my weight guessing 8sq inches. So I cant weigh more then 112lbs.

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    The point loads can be a problem. We have a high bay warehouse, on an upper floor, that we just had to redo the floor in because the point loads from the fork lifts tore it up. These lifts weigh 26k lb though. Since you are on grade it will probably be ok. Just keep an eye on it.

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    Quote Originally Posted by Pete Deal View Post
    The point loads can be a problem. We have a high bay warehouse, on an upper floor, that we just had to redo the floor in because the point loads from the fork lifts tore it up. These lifts weigh 26k lb though. Since you are on grade it will probably be ok. Just keep an eye on it.
    Thanks good to know. I’m guessing the lift traffic caused that upper floor to flex a bit, causing slight tension on the underside. Concrete has very little tensile strength so first signs of failure may have been concrete popping off the underside. But I’m no structural engineer, so who knows.

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    One point of view:
    Let's see, 6000 square foot warehouse, 2000 psf allowable load -- so you're good up to a total of 12 million pounds.


    Another:
    Your 24K forklift at max load, theoretically, would be 'balanced' on the front axle, give or take a few hundred pounds for steering traction in the back. Two non-pneumatic tires, 12" wide, say 3"x12" contact patch each, so 1/2 square foot. Calculates out to 48K psf.

    Chip

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    I see if i could find out how thick the floor was......Ive seen a few warehouse floors poured kinda thin,...saves a lot of money.If you check, the floor loading he specifies is pretty low.Your current fork would be well over his limit.The Cat fork seems to be about 4 ton cap,weighing 6ton+ load.I would think any rental warehouse should sustain a working 4 ton fork.Maybe you can include floor damage into a liability insurance policy.

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    Thanks. The worst case warehouse floor loading I can think of is pallet racks, which I’ve used over 15 years in five different ground-floor warehouses, without any evidence of floor failure. Let’s use the basic column area of one pair of uprights the way I typically load them. Each side of one upright frame I use has a bent steel hollow box beam of about 3x3” cross-section. There’s a thin steel foot plate welded across the bottom of each vertical box but I won’t count that since if the floor really failed right there it’d just fold up on its way down. So each upright frame with two vertical box beams is 2 x (3x3)=18 sq in. 2 sets for an assumed free-standing rack unit =36 sq. In. Assume 6 horizontal shelves are installed using the usual 96” welded box beams and wire screens (or plywood and 2-byes for us po’ folks.). Each of My 8’ x 42” deep shelves carries an avg of 3000 lbs including its share of the rack steel. So the whole unit weighs 18,000 lbs. pressing on 36 sq. In. Of floor = 500 psi floor loading, correct? Or 72,000 psf. So the landlord’s figure is more conservative than my testing by a factor of 36. I’m gonna take a wild guess that if the floor failed the landlord has an easy job showing the tenant broke the rules. I doubt that a lot of concrete floors fail under pallet racks or other typical warehouse items but there must have been some cases somewhere to cause landlords to bother to insert language in their leases.
    Last edited by Cannonmn; 12-16-2017 at 11:09 PM. Reason: Add

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    Slab on grade floors need to be designed on the basis of load , whether the load is static or moving, if moving how many load applications, and the quality of subgrade support. Search for "industrial concrete slab design". You get lots of hits. Here is an example: http://www.apd.army.mil/epubs/DR_pub...tm5_809_12.pdf.

    If the slab is not on subgrade, like an upper floor it becomes a more complex structural engineering issue.

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    If there are any unsupported areas under the floor from settling that lift with a load on it could break it.

    You'll know it if it happens. Makes a hell of a bang when concrete lets loose under a forklift.

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    Interesting info so far. If landlord can’t tell me the slab thickness I’ll ask other tenants, if no info there I’ll just hammer-drill one or two holes and measure. If slabs don’t vary significantly from one point to another maybe only one hole needed. I’ll be sure to avoid the under-slab 480 volt conduit and the plumbing runs.

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    The commonest cause of severe floor damage from load is ceramic tile warehouses...chemical damage is more of an issue for owners.I would just run the fork,and watch out for cracks....they form gradually as the subbase yields.A big lathe will be no problem for weight,but watch out for chemical damage from coolant.I have owned sheds,and I know the damage tenants can cause,including stealing all the electric fitout.I would be happy to cop a bit of floor damage in return for a secure tenant.
    ,

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    Part of our old shop has 4" of concrete, we've driven a forklift on it that weighs 75,000 lb empty without a problem. I've also fell through 12" of concrete with the same lift. What is under the concrete has much more to do with it's strength than the thickness.

    You'll probably be ok with what you are wanting to do, but you'll be many times over what the landlord says the limit is. The problem you're going to run into is if you do crack it, the landlord is going to claim that you overloaded it. It's a tough call, even though you should be ok, fixing a floor after you crack it could get expensive.

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    m16ty wrote: "... fixing a floor after you crack it could get expensive."
    Fortunately, fixing it "good enough" that it can hold 2000 lbs. is not difficult.

    Chip

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    I think more informative would be info on how old the building is and what sort of other tenants have been in there. If its old and there are no cracks, you are pretty unlikely to crack it with the sort of work you are talking about. If new and citing those sorts of numbers I would be cautious.

    See if past tenants have had big equipment moved in and out of there. The big lathe should be fine, they are heavy, but not that dense. Stay away from anywhere you know of conduit runs underneath with heavy loads if you can. It is the random pocket without under side support that will do you in. The older the place, the more likely someone else would have found that spot.


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