A ceiling that is actively dripping is doing you a favour, because water that finds a way through is water that is not accumulating above the plasterboard. The dangerous version is the one that has not come through yet, and the sign of it is a bulge rather than a drip.
Ceiling caved in water damage: move people, then relieve the bulge
Keep everyone out from under it and move what is below. A ceiling holding water is heavy and fails without warning. Where there is a visible bulge, a controlled release from below into a bucket, one small hole at the lowest point, is safer than waiting: it lets the water down in a stream you can catch rather than as a board and a room full of debris.
Turn off what you can, and look up
If a bathroom, kitchen or heating pipe is above, isolate that supply. If it is raining and there is roof above, you are waiting for weather rather than for a plumber. Electrical fittings in or near a wet ceiling are isolated at the consumer unit, because a downlight is an opening in exactly the wrong place.
What does mold look like on ceiling boards, and what it tells you
Fresh water staining is a recent event. Growth on the ceiling surface means the material has been damp for a while, because the EPA puts visible growth on wet building materials within 24-48 hours and surface growth takes longer to become obvious. A ceiling that is both stained and growing is usually reporting a slow leak rather than last night's storm, which matters for the insurance answer.
Dry the void, not the board
Most of the water sits in the insulation and on the joists above. Drying the room while the void stays wet is how a redecorated ceiling grows mold out of sight. Access holes, cavity drying and readings taken above the board are the difference between a repair and a postponement.
Questions people ask about water leaking from ceiling
Should I put a hole in a bulging ceiling?
Usually yes, from below, one small hole at the lowest point with a bucket underneath, after moving people and furniture away. A controlled release is safer than a ceiling that lets go on its own, which it eventually will.
Does a ceiling always have to be replaced after a leak?
No. Sound board that is now dry with light staining is frequently sealed with a stain blocking primer and redecorated. It comes down when it has sagged or softened, when the void cannot be dried without access, or when the water was contaminated.
What does mold on a ceiling mean?
That the material has been damp for a while rather than briefly. It changes the insurance conversation, because carriers treat sudden damage and a long standing leak differently, and surface growth is evidence of duration.
Can I find the leak myself?
Sometimes, by looking directly above and then working outward and uphill, since water travels along structure before it drops. Where the answer is not obvious, a moisture meter and a thermal camera find it far faster and far more cheaply than opening ceilings.
Is mold on bathroom ceiling surfaces a leak or condensation?
Condensation, most of the time. A bathroom ceiling that grows mold evenly across the cold part of the slab is a ventilation problem; a defined patch with a stained edge is a leak from above, and the two need different work.
How long does water damage restoration take on a ceiling?
Drying the void takes days rather than hours, and the repair waits for it. A board that stayed up dries in place; one that came down is a rebuild, and the equipment leaves when the readings say so rather than on a set day.