Concrete base / type one base

[bigwest]

Never had to ask myself this question before so would be grateful of any advice. We've just dug out an old patio in preparation for a new one, in doing so we discovered that half of the old patio is laid over a substantial and seemingly solid concrete slab about 3 to 4 inches thick. The rest is just a mess of slabs on soil, bit of hardcore, sand etc. so obviously needs to be dug out for a new base.

The new patio will cover the whole area, so is it OK to use the concrete slab as it is and butt up to it with a new base of crushed stone?

Just wondered if there would be any problems having two type of base under one paved area? Rather not break out the old slab as it's some size but rather not risk any future problems.

Any thoughts gratefully appreciated.

cheers

Andy

[Tony McC]

If it were a driveway, then there could be a problem of difgferential settlement with havinbg one area of paving over a rigid base and the other over flexible, but as it's only to be a patio, I reckon you should be OK as long as you thorougly compact the new sub-base.

[bigwest]

Thanks Tony, will give it a proper wack!