New Damp

ANGLICANPAT

Bungalow with concrete tiles. None seem to be broken as far as we can see . Ridge tiles look ok through binocs, no light showing in that area from loft view . Mould patches have appeared fairly suddenly over a few weeks , in the ceiling corner of the bedroom party wall .Its on ceiling and both wall surfaces, covering about eight inches fan shape into each.

Rest of the walls beneath that top patch are completely clear ,until you get towards the skirting, and then theres exactly the same thing on wallsboth sides of the corner immediately above the skirting , again about 8 inches fanned spread. We have had horrendously heavy rain so it could have blown under the roof sides , but then surely the damp would only be coming from top down.

Its never happened before, but if it were a matter of damp being caused by drying clothes in the house , a lot of heat and not enough ventilation, would that produce mould in just corners top and bottom?

Would have thought it was too much of a coincidence to have a roof leak and a failure in the front wall dampcourse at the same time, so is there any other reason why mould would appear only top and bottom suddenly? If a roof leak, I would have thought everything would start at the top and work down ?
If theres no apparent break in tiles, where would I ask a roofer to start, how would he go about finding the cause if no breaks? -or is it a damp specialist we need? Thanks for any insight.

SG27

Sounds like condensation. Occurring in corners where air circulates less and around the base where the wall will be colder. It's quite common for condensation to form in these areas.

force_ten

as above sounds like cold bridging from outside, the wall in the corner ot the room is cold and when the room is used condensation is forming on the cold area causing mould

Dank

We had mould upstairs in a corner behind furniture. Initially it was cleared using Ebac dehumidifier. I then ducted cooker hood to outside and there was no further need for dehumidifier.

So called surveyors employed by damp proofing firms will always find damp requiring expensive work. Have a look at Building Research Establishment site.