Do i have to put a pvc sheeting down on my existing indian stone patio before i lay my 4 inch 2m concrete slab on top of it. This is a hot tub base,
I have to do this as there is a 8cm down to a 12cm slope on the patio .
So need a 2m x 2m slab with mesh in to support it.
The existing patio is only 3 years old and sits on a foot of concrete.
I can either just put the frame/form down on 1200gsm pvc sheeting to protect the stone underneath or just pour the c40 concrete in on top of the indian stone within the form/frame.
Im just worried that the sheeting will not allow the concrete to sink down and fill the uneven riven tops on the flags.
If it has to go on the flags then what do i use for bonding the surface so it keys to it.
If done this way ,will if crack as it starts shrinking while drying because it is keyed to the stone patio underneath..
Advice would be app.
