Garage floor slab and DPM detailing

[flanagaj]

We are having a Radon membrane (but I suspect the same applies for a simple DPM) and am just about to put my order in for pre formed Visqueen units.  As the floor slab protrudes across the 350mm wide inner leaf/cavity and outer leaf, I am confused as how you stop the slab getting damp from rain water falling on the outer part of the slab which sits outside the garage door, which then creeps internally inside the garage.

Below is an image of the pre formed corners, but even if you did not have pre formed corners and cut and taped the DPM around the opening, you still have the issue of the slab running continuously through the opening and outside.

Do you simple cast the slab in two sections and have a dpm upstand on the inside and have rebar mesh poking through to the 350mm wide opening section?

  

Edited yesterday at 15:05 by flanagaj

[Oz07]

I've stopped mine short before and used kerb units on edge for the final bit. I don't think it matters massively

[flanagaj]

2 hours ago, Oz07 said:

kerb units on edge

Sorry, but what are kerb units?

[Russell griffiths]

Turn the membrane upwards against the outer side of the outer leaf of blockwork, then lay your driveway up against it. 

[Oz07]

Like these charcoal blocks. Basically as @Russell griffiths says finish slab inline with internal wall