porch footings

[grizzlebear]

Hi
Im having a go at building a block/rendered porch this year.
We get a lot of cold in the front because our front door has a large glass panel. My thought is do a double block and then it might give a little insulation.
So, the question to start is this. The front drive is tarmaced from 1960, i have had a little test dig and under the tarmac the hardcore just keeps going past 12" .How deep will i need to dig down for the footings/will i just be able to cast the base srtaight on this hardcore?

cheers for any help

 

[noseall]

How deep will i need to dig down for the footings/will i just be able to cast the base srtaight on this hardcore?

Not if you want it to last.

You will need to dig down to decent ground, whatever depth that may be.