Crack in ceiling

[Laura2211]

Hi there
There has been a small crack on the ceiling of my kids bedroom for a while now but over the past week it has got bigger & started to sag. I’ve obviously moved them out of the room but unsure what to do. I guess the ceiling needs replacing so is that a builder I would call? And how much would this cost roughly?
Sorry to sound thick but I really am a complete amateur when it comes to building works and issues 🤦‍♀️
TIA

Is there anything in the loft that has slipped between the joists to make the crack start cracking?

Do you have a leak in the loft?

Go into the loft to see if anything is amiss. It looks like a plaster problem caused by pressure of something resting on it, if nothing appears wrong, I’d pull the looses plaster off for safety , it’s going to come off anyway. You could call a builder or plasterer for advice.

Agreed. Get in the loft and pull up and boarding/insulation in that area.

If it's starting bulging after the recent cold snap, you might have a pipe that's frozen and started leaking slightly.

Leaving aside the cause of it. The ceiling can be plasterboarded over & skimmed very quickly & cheaply. We've done it in two rooms. If you had hairline cracks that were annoying, you could paper the ceiling with 'Wallrock' it's a lining paper made like felt - from fibres. That can stretch in any direction without tearing. We've also used this with great success.

If it’s not damp or there isn’t a tide mark, then unlikely to be caused by water.

could it be damaged by the kids and they’re keeping quiet?

as for repair , it could be as small as a square of plasterboard just larger than the crack but will need an artex type finish. You could diy depending on how professional you want it to look.