How much weight can a slab hold?

[chicane]

Is there some sort of calculation to figure out the maximum sustained weight a slab can hold before it cracks (or even collapses). In other words Length, Width, thickness and the PSI of the concrete used to figure out this weight?

 

[bmwpower]

Don't forget rebar. It greatly increases weight capacity of the slab. I don't know the calculation. Any structural engineers out there??

 

[Ironcrow]

If the slab is sitting on compacted soil then the sustained allowable load will be the compressive strength of the concrete or the load bearing capacity of the soil, both in the couple thousand psi range.

 

[PAToyota]

Yes, there are calculations... Could dig out my textbooks... But would then have to figure out how to post all the greek letters...

 

[chicane]

Yes, there are calculations... Could dig out my textbooks... But would then have to figure out how to post all the greek letters...

OK, well without going through all of that on a typical 4"-6" slab, how much weight will it hold?

 

[Junkman]

4" slabs are usually poured with 3500 PSI concrete. Add some rebar, and you are probably up to 4500/5000. My 8000 pound rated Bend Pak 4 post lift has 4 ... 1 foot square steel pads that support that 8000 pounds. That equals about 9800 pound total.... lift and car. Divide 9800 by 4 and you have each post supporting 2450 pounds on a 1 square foot of concrete, and nothing has cracked yet.

 

[chicane]

4" slabs are usually poured with 3500 PSI concrete. Add some rebar, and you are probably up to 4500/5000. My 8000 pound rated Bend Pak 4 post lift has 4 ... 1 foot square steel pads that support that 8000 pounds. That equals about 9800 pound total.... lift and car. Divide 9800 by 4 and you have each post supporting 2450 pounds on a 1 square foot of concrete, and nothing has cracked yet.

Cool thanks, so that's what you are parking on (4" slab at 3500 PSI )?

 

[PAToyota]

OK, well without going through all of that on a typical 4"-6" slab, how much weight will it hold?

It has been a long time since I've bothered to do the calculations. It would help to know what you are trying to accomplish. As Junkman states, a standard 4" slab with reinforcing - I would spec 4x4x4/4 wwf - is most likely going to support anything that you dish at it. I've done truck garages where we went to a 6" or 8" slab with #4 bars at 8" and 6" oc each way respectively to support greater loads.