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Mould accumulating in our loft conversion
We’ve noticed we’re getting mould accumulating on the outside and inside of the door to the crawl space in our loft conversion.
There is no heating up there yet but I’m concerned that wont stop the cold draught creating pockets of condensation. I haven’t treated the doors so obviously I can do that to protect them but I’m more worried about the damp itself, which obviously won’t be stopped by sealing the wood.
The inside of the crawl space isn’t insulated at all. We grabbed some insulation and membrane (out of the skip because the builders were just throwing away the excess). Will insulating it help or is it the lack of heat that’s the problem? Any suggestions on how to resolve this would be much appreciated. We assumed it would be insulated by the builders but looking closely it’s not mentioned on the scope of work, so now we need to work out a plan. Obviously we’d like to make sure it’s not creating damp in the room but I’d also like to use the crawl space for storage so would rather it isn’t damp in there either ideally.
Also to add, I know ideally we would’ve used more breathable materials up there but we couldn’t find a builder willing to even consider using something other than the standard, glass wool, plasterboard etc scenario.
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7 Replies
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Is it very recent plaster? A lot of moisture comes out when that’s drying. We had tons of condensation in mornings after windows were closed at night and no heating in the room.
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The plaster went in quite a while ago, probably 2 months now so has been dry for a while. The windows only went in just before Christmas and I’ve been tiling gradually though so it’s been pretty inconsistent on moisture levels I think. Hopefully it’s down to excess moisture and cold though, this is sounding likely from the other comments too, so going to do our best to warm it up a bit (radiators aren’t going in til end of January so just got a little electric heater up there now) and see what difference that makes.
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Most attics aren’t heated, but they must be insulated, including the actual loft hatch itself.
It’s pretty shocking work to be honest. Why go through the effort and expense of a loft conversion and not have it properly insulated.
Your designers really should have known better. It’s recommend getting a thermal imaging scan done (our RICS surveyor did this for us for about £300), because it seems likely that you have cold bridging causing damp. Rather than pulling things apart, get the imaging done and then target the areas actively losing heat.
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Hi, for building regs if you are following them, the floor of the crawl space must be insulated as it is the roof of the room below. Without this the room below will end up with mould on the ceiling and you will feel alot of heatloss. I’d recommend installing tile vents at high level and eaves tray vents at low level in the crawl space as you must ensure the crawl space is still well ventilated as it’s a cold roof design. If it’s not ventilated then you will get condensation in the loft area and timber rot.
The stud walls to the crawl space should be insulated too. You should have draughtproofing strips all around the doors to the crawl space.
Get an electric heater in the loft room and have it on twice a day for an hour each, you need to heat the air to take moisture out the room, then ensure you have window trickle vents open or extractor fans running to remove this moisture laden air. To stop mould you need heating, ventilation and extraction. Don’t decorate the rooms until the mould is gone and under control.
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I’ve got the same situation but about a decade on from the building work and this is great advice. We haven’t got draught strips in the door and I don’t think the crawl space has much ventilation, and indeed, there is a bit of condensation occasionally.
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Thank you so much, this is so helpful, I will start getting this things done. We have had a heater on up there at points, but mostly when I’ve been working up there – currently doing tiling when I’ve had a spare moment over Christmas, so it hasn’t been consistent each day. The builders seem to be very careful about building regs and we have a private company involved for them so I imagine that means there is insulation under the boards and there definitely seems to be some within the stud wall surrounding the doors. Would you recommend lining the inside of the tiles with glass wool insulation and membrane or does that reduce the airflow too much?
We’ve also been looking at some natural products from Mike Wye to do this which are more breathable, but again, don’t know if that will restrict air flow too much?
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The crawl spaces are built as cold roof meaning they are designed for air to enter the space, if you insulate along the tiles then you will trap moisture, you only insulate at rafter/tile if the space is a warm roof meaning there is no airflow and it’s part of the heated space.
As long as the stud walls and the loft floor are insulated to regulations then that’s enough just ask building control if they have inspected and approved these elements.
It’s likely then you have alot of moisture rising up into the loft room from the house below. Heating will help but definitely get the extractor working in the bathroom up there and open the window vents and this should balance it all out.
The extractors and trickle vents work together to move air around the house, vents bring fresh air in when extractors come on and pull air out. Without both you get stale air sitting in rooms which can add to moisture. Turn the heating on for an hour then switch the extractor on for abit and you will get the moisture out whilst it’s not in use up there
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