I have a 10x12 shed that rests on a concrete slab. Unfortunately the slab sank about 3” on one end, so water in the spring actually creeps up onto the slab and rots away the wood. I’ve been told that it can’t be mudjacked because of the footing that is thicker around the edge. The only negative I’ve heard about pouring a new slab on top of an old one is that cracks from the old one will just transfer through to the new one. There is nothing wrong with the original slab other than that it sank. Would it be safe to lift the shed and pour a new slab on top of the old to get it above grade again?

What's to stop the existing slab from further sinking when you add a thousand pounds to it?
Your best bet would be to consider calling a foundation repair company to have them jack it up properly although you may not like the price.

I don't agree with the "can't be mudjacked because of the footer". If it settled or sunk it can be lifted. I think you got some bad advice.

quote:

Originally posted by 400m:
There is nothing wrong with the original slab other than that it sank.

The fact that it sank means there was something wrong from the beginning. 3" over 12' is significant. You might be better off fixing the water issue & living with the uneven slab until it's time to replace.
For DIY, once you lift the shed it's not that much more work or $$ to bust out the concrete & pour new vs pour over an already unstable base. Hell if you're lifting the shed, it might be time to find a new spot that isn't as wet & then you'll have an extra 10x12 patio.