Roofing

Extreme condensation on ceiling of flat roof extension

Anonymous user 09/03/2024 - 3.17 PM

We moved into a 1960's mid-terrace ex-council house in May this year which has a small extension to the rear of the property. We were told the flat roof had a fairly new felt covering. Since the nights have got colder we have noticed that the ceiling of the extension is wet and large water droplets are forming all over the ceiling and mold. The condensation seems contained to the ceiling only and the walls are mostly fine only the top of the walls near ceiling are suffering mold problems. We had assumed it was a ventilation issue so got an electrician to fit humidistat extractor fan that runs all the time and boosts if humidity reaches a certain threshold but this doesn't seem to have made any difference. I would have expected that any humidity trapped would be sucked out by the extractor so slightly stumped to why this hasn't worked. The extension is much colder than the rest of the house and is not heated in any way. The ceiling is very cold to touch. There is a door that isolates the extension from the kitchen of the main part of the house which we keep closed most of the time or ajar to prevent heat loss. The kitchen has no ventilation other than the cooker hood and the kitchen windows are kept closed as they open out onto a lean-to conservatory so I have wondered if any of the humidity generated in the kitchen is escaping to the extension, though the kitchen opens out to the rest of the house too so plenty of space for humidity to escape to. The extension is used to house our washing machine and I don't believe the washing machine is the cause of the condensation. I have no idea what is causing the condensation so any advice and help would be appreciated as we don't want to keep showing money at new ideas like the extractor to find they don't make any difference.