Garage ceiling I-beam, how much weight can I hoist on it?

Depends on what it is already holding up above.

Well few builders will put a beam in larger than necessary to carry the weight of the structure. You need to know what it is already supporting.

Once you determine that, I'd still put in a vertical support under the beam while I was doing the lifting.

I think they did in this case: a 12" I-beam can carry an awful lot of weight... but I agree with the recommendation to have an engineer do a load calc, especially if the OP is planning to use this I-beam for hoisting auto engines.

And I would make the vertical support have a very large base in order to NOT crack my concrete floor with a point load.

You can stretch a string under the beam and see how much sag you have already. If there is very little sag, then you can use the string to keep track as you lift your weight.

Or you can spend a couple of thousand and hire an engineer. Your choice.

Jiml

Good point. :)

Say you use a 4x4 as the support. Isn't there a max base size that's going to do any good? If it was 3/4 plywood, at some size of the plywood and load, woulnd't the ply "buckle" upwards and reduce the area that is transfering the load to the concrete?

Of course! But you don't have to use plywood, in fact, I wouldn't use plywood. I would use a steel base with reinforcing gussets to transfer the load to as large an area as possible and place that on a sheet of plywood.

Of course, it is also possible that the I beam in question is large enough to support whatever he is going to lift without any help at all. Impossible to determine from here. But if it isn't, and you use a support, then you had better spread the load, hope there is a footing under that point, install a footing under that point, or just hope for thick concrete and no cracks.

i had a 12" 25ft i beam 1/2" thick in a garage and we pulled engines out of cars and lifted the front of some big lawn tractors and it never budged.i did do most of the lifting within 10 feet of the wall if that matters. i dont think any of the engines were over 1000 pounds..when you lift .you can see it if it sags ,just put some kind of homemade guage on it . lucas

Do a test by hoisting your mother-in-law up there. Come back in a week and see if she's still yakking.

Ok so could someone tell me what the center deflection would be with, for example, a 1000 lb center weight applied to this beam? I used to have a beam calculator, not sure where it is now.

Thanks

Dean