I've got an 1890s house in London. We started getting some penetrative damp through some of the upstairs walls so I've had a look in the attic to check if there's anything going on up there.

It looks like all the rafters have got white mold on them, though the internet's say it could be efflorescence. I'm guessing that me replacing the insulation in the ceiling joists a few years ago has contributed to this.

Luckily I have one window in the attic, but it's a small window and a large attic, and it's currently winter and quite rainy.

All my Google searches are turning up damp companies who surprisingly don't respond to phone calls or emails so I ask the more trusted stackexchange: what should I do, if anything, about the attic?

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  • Good thing you commented, I've posted an answer. Hopefully some help.
    – beirtipol
    Nov 21, 2020 at 20:12

1 Answer 1


I had 2 builders come out to survey and both pointed out that I had recently reinsulated the loft. The issue was that there was no ventilation in the loft so the damp air was trapped up there by the new lovely fat insulation I had installed. The solution was to install roof vents to allow some airflow in the loft.

It cost me about £1500 to get this done but that included some remedial work to the chimney to try and address a penetrating damp issue in one of the bedrooms.

It's been about 6 months and I was told it would take some time to clear up so I'll recheck it again in the new year.

  • Thanks for coming back and reporting your results!
    – Matthew
    Nov 21, 2020 at 21:37

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