Evening all, thanks for reading this. Just to be clear, I'm an absolute amateur at DIY, but have bought a flat and it needs a lot of work. It's a 40s/50s ex-council block, lots of redbrick and cement etc. There was a raised section in the hallway floor, approx 15mm high by 250mm wide, running diagonally across. Similar situation in the bedroom the two follow the same line, I'm assuming they're connected. First thought was to use self leveling compound to raise and level the two floors but a mate advised against, and suggested I chisel out the raised area and back fill/level the hole. So I bought a cold chisel and set to work... I found the floor was in several layers. On top, a dark red cement type material (~15mm), underneath that a cement coloured cement type material (~5-15mm, but this was only in places), and below it all, concrete. The middle layer was all broken and dusty in large part. Worryingly, I also found an old pipe that must be causing these problems. The pipe looked very old and corroded (had small holes rusted in it), and the building hasn't exploded yet. I'm now left with a sizable hole in my hallway floor. Perhaps 60mm deep at its deepest. Approx 750x300mm at surface. Was thinking to fill with some kind of cement at the bottom, leave to cure, then self leveling for the top 5 - 10mm. Carpet or, if it's level enough, laminate will be going on top eventually. Does this sound reasonable? Anything obviously wrong with the plan? Thanks in advance for any advice.