pouring a concrete slab on existing concrete + hardcore-

Parkender

I need a concrete slab for a new shed. I had an old slab but want to level it and extend it onto where some hardcore is. Anyone think of any issues with that? Would imagine it will only be 20mm higher than whats there currently.

hawkeye_bmr

What type of shed are you talking, wooden/steel or block shed?

I would say if you add 20mm to the top of the old slab, where the new one meets it will be a weak point and with settlement it will shear/crack along this.

Any impacts or heavy point loaded weight will probably cause cracking on the 20mm side also.

It will also be hard to get a good finish on the 20mm side as the aggregate will be very easily snagged when floating it.

Is there an option to break-up the old slab and use it as hardcore?

Parkender

hawkeye_bmr wrote: »

What type of shed are you talking, wooden/steel or block shed?

I would say if you add 20mm to the top of the old slab, where the new one meets it will be a weak point and with settlement it will shear/crack along this.

Any impacts or heavy point loaded weight will probably cause cracking on the 20mm side also.

It will also be hard to get a good finish on the 20mm side as the aggregate will be very easily snagged when floating it.

Is there an option to break-up the old slab and use it as hardcore?

Thanks for your reply. It’s a steel shed. Just going to be a storage unit so not overly fussed on finish etc. Just want it to do the bare necessities I suppose.

hawkeye_bmr

Parkender wrote: »

Thanks for your reply. It’s a steel shed. Just going to be a storage unit so not overly fussed on finish etc. Just want it to do the bare necessities I suppose.

If you could get say 50mm onto of the existing slab it would be a lot easier to get a good finish and less chance of it cracking.

Plus if you get plenty of hardcore compacted down there's less of it sinking/settling at the heavier section