got an unusual problem in a rental property. House is 120 yrs old, mid terrace. Has an aluminium door straight off the pavement then a hallway with lino tiles over assuming concrete (its not floorboards) Theres a bulge that is big enough for the front door to scuff heavily over when it opens. I want to break the bulge up with a breaker then level but am a bit nervous over whats causing this bulge before I dive in. Anyone any ideas?!