Can I put 804 gravel on old concrete or should I break it up first

cianw

Hi, I'm currently preparing a base for a new concrete slab patio. A portion of the area has an old piece of concrete acting as a path around the house and it has a heavy slope on it.

The slab I intend to pour will be 100mm thick so I need to level up the area of old concrete too.

My question is should I remove this old concrete first or just throw down the 804 and compact it on top. On the very right by the house is 4inches so I don't need any gravel there but I need up to 3 inches back to where it meets the gravel on the left.

Will the 804 gravel be "loose" on top of the old concrete and it won't stick as good into soil etc? Or should I be ok.

standardg60

FWIW you're going way too close to your DPC level at that planned height. The standard minimum is 150mm (which your existing concrete is at) , so you may need to rethink that.

Fine Cheers

Good point re DPC. Assuming house floor level is same as dpc, is this the same level as your plinth in photo ?

Why use 804 at all ? More experienced posters can advise but could you start off with 75mm concrete at house and increase as necessary ? As you have asked, it might be better to remove depending on your dpc level but obviously that is a good bit more work.