Roofing

stain in middle of ceiling bathroom

Anonymous user 28/02/2024 - 3.25 PM

In the bathroom of my loft extension (dormer)a stain appeared in the middle of ceiling, in the bathroom, another stain appeared in the corridor just above bathroom window. ..my builder concluded without inspecting the flat roof that it was condensation which was contradictive with information I found and other professionals inspection...After a battle of two month roofer came to inspect the flat roof, no evidence of leak or water infiltration was found.roofer told me that leak or water infiltration could be very hard to find on flat roof and I just should keep an eye on stain. It seemed to not evolve so I decided to follow advise of my builder and paint the ceiling. ..less than a week after painting , a yellowish line appears where the stain use to be. .used the bathroom only twice since I have another one. ..bathroom was well ventilated when in use. ..Builder advises to use a stain blocker but I read everywhere that it should be use only when source of stain has been clearly identified and properly dealt with and I don't feel it has. I really need some advise about what the best next step . Photo can be provided on demand UPDATE: Thanks both for your reply, there were very helpful, this is a cold roof and where the stain is, this is a very cold spot compare to the rest of the ceiling, so it seem consistent with an incorrect insulation at that spot which would explain condensation in the middle of ceiling. What is the best solution to correct this?