cavity concrete block wall on top of an existing stone wall

[afj24]

Helo,
I am building a cavity concrete block wall on top of an existing stone wall to form a flat roof.
What would I require regarding damp course, cavity tray, insulation etc?
Thanks in advanced
Alan Jones

[thedoctor]

Horizontal Damp course only required to stop water rising up through blocks and if you are more than 150mm off the ground when you start your cavity wal its not required. A cavity DPC is only inserted over windows or any opening where water can potentially get into the cavity. If the wall id continuous up to the underside of the roof, no DPC is required. The insulation required depends on the building and its use, talk to your local building inspector re this.