Flat concrete raft-how do I prevent damp under first course of blocks?

[Boycey]

I have poured a reinforced concrete raft for a large double garage on the advice of building control. It is flat, ie there is no step for the outside skin to sit on. This was clearly a mistake ! Is there a good way to provide proper DPC protection at this late stage or am I totally stuffed ???

 

[myownnme]

While I've never heard of a building department allowing or advising a concrete s.o.g. to bear the weight of the walls without a thickened edge or continuous footing, it doesn't really surprise me either. It seems that you could trench around the perimeter taking care not to damage any vapor barriers (which I suspect are lacking anyway) and pour a grade beam/stem wall or what ever you like to call it. This could be water proofed and perforated drains could be utilized to help carry away moisture.

 

[Boycey]

Thanks for this, but what is a stem wall ?
The raft was thickened at the edges but there was no step on the outside edge to build the outer skin of blocks on. This meant that both skins sit on the concrete slab over the thickened portion. There is a PVC membrane under the whole thing.