Repair concrete floor

[Adam78]

I have just purchased 1930s semi and have started replacing the kitchen units. The kitchen has a concrete floor with a bitumen layer on top.

Upon removing the cabinet under the sink I've noticed a section of the concrete slab is missing. The hardcore/ground where the concrete is missing appears to be unusually moist too. Can't see any visible signs of a leak - you can just make out in the pic the first course of bricks just below the DPM appear wet.

Whats the best way to repair this concrete. Do I just cement over the section and apply some liquid DPM on top. Any advice would be appreciated.

 

[ree]

OP,
Your, presumably original, concrete floor lacks a membrane (a DPM).
There's no signs of rising damp so the floor seems to be working - the wet we see is ground water, & the DPC and conc floor are keeping it in check.

You could open a plastic rubble bag, and use it to form a mini DPM - then pour in a Builder's merchant's bag of dry ready mix concrete. Level it off with the floor and DPC.

 

[Nige F]

I have just purchased 1930s semi and have started replacing the kitchen units. The kitchen has a concrete floor with a bitumen layer on t

the bitumen aka tarmac layer is the damp proofing.

 

[foxhole]

Given the location of the waste pipe possible historic leak, or maybe still is.

 

[jj4091]

Is that waste pipe going through the wall to the outside. Is it a cavity wall or solid.If it is going outside you may need to check it is not flowing into a broken drain and soaking the footings on the outside and then perculating through the wall.

 

[Adam78]

Is that waste pipe going through the wall to the outside. Is it a cavity wall or solid.If it is going outside you may need to check it is not flowing into a broken drain and soaking the footings on the outside and then perculating through the wall.

Its washing machine waste pipe that does go through a cavity wall to the outside into a drain. THe kitchen sink waste and rainwater downpipe all drain into the same drain outside which is located roughly where the wastepipe in the pic above exits.

I've just got hold of some leak tracing dye which i'm going to pour down into the drain to see if it is indeed due to a broken drain.