Damp proof injection before concrete slab?

[Lounge About]

Hello fellow DIY'ers

If I was to put a new concrete slab down in a room that has signs of damp in the walls would it be best to inject the walls before the slab goes down

The floor will be constructed thus

View media item 48879
Any help would be appreciated

 

[noseall]

It won't make any difference as the injected dpc should be one brick above ffl.