Chicago two-flats share stacks, joists, and often a single water main. A split in a kitchen supply at 4 a.m. will show as a bedroom ceiling downstairs by 4:20.
Shut the main if you cannot find the local valve. Call the other household. Water does not care whose name is on the lease.
We contain the downstairs, extract the upstairs, and meter both units. Insurance files that treat this as one room always come back around. Two addresses, one event, one moisture map.
Plaster ceilings can hold a surprising amount of water. We do not punch a random hole and leave. We open what the meter says is wet, then close it when it is not.
