I just dug out part of my screed to re-route my radiator pipes.
On the edge of the floor (from the wall going in by a bricks width) a few inches down is the top of a red brick course covered in a thin light-blue plastic.
I'm not sure why there is a brick course jutting into the floor.
But the problem is I damaged this thin blue plastic and I want to repair it before filling the hole in with concrete.
Can I spread silicone over it? Or should I just lay some black DPC roll over it? Or can I just lay a piece of black bin bag over it - considering it was such thin plastic in the first place?