Foundation slab over existing concrete?

[Dancing Bear]

Re: Foundation slab over existing concrete?

OK - the soil beneath the patio was compacted prior to pouring, so it should be pretty solid. I'm liking the idea of sawing out the foundation area so that it moves independently of the rest of the patio.

[Ken524]

Re: Foundation slab over existing concrete?

DB,

Pouring concrete on top of concrete won't improve the foundation below the patio (that eliminates the first 2 choices). If the slab is on top of dirt, there could be hollowed out areas from drainage and settling; especially if it wasn't compacted. This could lead to some serious cracking.

Your oven will way a ton. More than a car. No way would I put a car on my patio. It's just not designed for the weight.

My first choice would be to remove a section of the patio (no need to remove the whole thing) and put in a compacted gravel base, followed by rebar and 5.5" of concrete.

2nd choice is Dmun's idea (pretty darn clever!). Have someone saw an area around where the oven will be.

[Dancing Bear]

Re: Foundation slab over existing concrete?

Bare soil - what are the potential problems?

[dmun]

Re: Foundation slab over existing concrete?

The worst case scenario is that the uneven pressure on the existing patio could cause it to crack. You could always have a concrete cutting place cut a joint between the oven foundation and the patio, if a patio crack is going to cause agitation.

Also, is the patio poured on a proper bed of crushed rock? A lack of drainage could cause a problem. A lot of patios are just poured on bare soil.

[Dancing Bear]

I am planning to build my oven in a spot where there is already a 3-1/2" reinforced patio slab. Should I:

1. Pour an additional slab on top of it (and should that be the full 5-1/2", or would another 3-1/2" be OK),

2. Remove a section of the existing slab and pour the foundation from the ground up,

Or

3. Just leave it alone and build on top of the existing slab?

I'm favoring option 1; does anyone have insight to provide?

Thank you -

Bill Stewart