dpc type

Hello all. My first post but have been browsing the site for years. Intended to pave out the little front terrace but for the life of me can not figure out where the DPC line is so I can build it 150mm below it. It is a property built in the 1920's with a cavity wall. I've dug out patches of...

Hello Can anybody identify what type of damp proof course this would be. It just looks like a thicker layer of mortar from the outside.