ᐅ Sealing and insulating the base coat plaster

Hello, since I am building a new terrace, the base plaster will extend 20cm (8 inches) in height. Because the base plaster (painted with some older paint showing wear) will be in contact with gravel or frost protection, I plan to apply bitumen coating to the plaster and then install a dimpled membrane. My question is whether this approach is correct. I would like to thank you in advance for any suggestions and solutions.

Regards, Frank

Bitumen is fine. What do you mean by dimpled membrane (also known as drainage membrane or studded membrane)?

The old paint will likely need to be removed beforehand.

If it is solid, not necessarily. Only what is flaking off.