possible leaking chimney flashing?

[chimchimineycheroo]

We live in a 3 story end terrace, and the top floor has a bathroom we've never really used (terrible water pressure, rubbish toilet that never flushes properly, etc).

I'm now in the process of ripping it out, and have discovered damp patches behind the built-in cupboard and black mould under the tiles. It looks as though all the damp is coming from around the chimney breast, and I'm thinking that since this room is on the top floor of the house and right under the sloped roof, it could be the flashing is leaking.

The plaster around the chimney breast feels damp, and has been coming off in great chunks. The ceiling where it meets the wall next to the chimney breast is very soft. (was tiled over previously)

Having never done any significant DIY before, what would be our next steps? Any help/advice/experience gratefully received.

Get a roofer to have a look at it. There aren't many other options.

I think I would get a surveyors report to see if the roof is damaged where it meets the chimney. Is there a loft? What condition is that in or is the top floor essentially loft space? Clearly it needs inspecting from the outside and I wouldn’t do anything until you know exactly what the problem is. You can then get quotes for repairs based on accurate information. You need a roofer as this isn’t a diy job in my opinion.

We'll climb into the loft later today and have a look. It's a small loft, as the top floor is built right into the roof, but I think we can crawl in there.

Our neighbours have recently done up their roof so I'll ask them for a recommendation.

Thanks.

Is the chimney vented? People brick fireplaces up without putting in vents and this can cause problems internally in the flue with condensation and damp.

My chimney leaked badly (water running down it, in the loft space)- builders could find nothing wrong, in the end someone suggested the stones it was constructed of were too porous, so I got someone to spray Thompsons Ultra Seal onto the outside chimney stack and this resolved the issue. So if you cannot find anything else wrong this would be a cheap fix to try.

Thanks for the tips.

Had a quick chat with a neighbour who recently had their roof done, and the roofing company is owned by her brother! She's sending him round tomorrow, so that's convenient. Will update if anyone's interested.

Yes update us. If the neighbouring roof has just been done then that might have disturbed yours unless it's obviously a long-standing problem?
Also be aware chimey flashing is likely to be lead which is worth a lot. Sometimes if roofers are up on the adjacent roof they might be tempted to help themselves to the lead.
So important to employ reputable roofing contractors.