Stupid garage DPM/DPC question

[VDubDan]

My house currently has a very grim, 1950's precast garage. My intention is to knock this down and build a lean-to garage.

For future proofing, and because I intend to store a classic car, I'm thinking to do a traditional extension build - i.e., rendered block cavity wall (rendered to match house), trench fill foundation, then concrete slab floor.

The bit I can't get my head round is the DPM detail for the floor. The DPM would normally come up to lap into the DPC, with the FFL matching the DPC.

Obviously in my garage that isn't the plan, I guess I'll do the DPC 150mm above ground, but I need the slab at the ground level. What do I do with the DPM? I don't want it lapped up, that'll be silly

 

[noseall]

My house currently has a very grim, 1950's precast garage. My intention is to knock this down and build a lean-to garage.

For future proofing, and because I intend to store a classic car, I'm thinking to do a traditional extension build - i.e., rendered block cavity wall (rendered to match house), trench fill foundation, then concrete slab floor.

The bit I can't get my head round is the DPM detail for the floor. The DPM would normally come up to lap into the DPC, with the FFL matching the DPC.

Obviously in my garage that isn't the plan, I guess I'll do the DPC 150mm above ground, but I need the slab at the ground level. What do I do with the DPM? I don't want it lapped up, that'll be silly

Lower the internal DPC by a course of brick (or whatever) and maybe add a cav’ tray at external DPC level.