Condensation in roof space of loft conversion

Discussion in 'Other Trades Talk' started by linzey123, Jan 21, 2022.

  1. linzey123

    linzey123 New Member

    Hi I am desperate for answers on the reason for the condensation building up in the roof space above my loft conversion.

    It’s is a large loft conversion built roughly 4 years ago and during cold weather condensation is dripping through the from the underside of the flat roof onto the insulation and finding it’s way through the plasterboard into the bedroom.

    The problem was so bad 2 years in that the roof had to be replaced and they put several mushroom vents into the roof to help with ventilation. There are soffit vents at the back and ridge vent toward the front of the space.

    I thought the mushroom vents had solved it apparently not as in the last couple of weeks it’s started coming through again.

    I started airing the room more each day leaving a window open and turned down radiators to ensure it’s not too hot in the bedroom having read online but this does not seem to have made any improvement.

    only access to see into the roof space is to pull down the down lights and put a camera up…obviously what I can see is limited but you can clearly see the wet in the spaces away from the spot light wholes.

    i am at a loss as to what the problem is and who to contact to help me solve it.

    any advice would really be appreciated.
     
  2. AnotherTopJob

    AnotherTopJob Screwfix Select

    Presumably there's a good air gap above the insulation?
     
  3. linzey123

    linzey123 New Member

    What qualifies as good? It’s difficult to measure but probably around 5 inch gap between insulation and roof
     
  4. AnotherTopJob

    AnotherTopJob Screwfix Select

    Sounds plenty of air gap.

    The key is cross-ventilation from front to back, so there could be a restriction at the soffit or ridge, or in the structure itself.

    To be effective, the mushroom vents need to promote airflow rather than just let air in.
     
    doesitmatter likes this.
  5. doesitmatter

    doesitmatter New Member

    As AnotherTopJob said, cross ventilation is absolutely vital. Air needs to come in to go out.

    Quite regularly, you see people installing insulation in lofts and going right to the edge of the roof, thus stopping air from getting into the soffit or ridge. This means less air can get in, and inevitably, condensation builds up. If there's any way to check that, it's worth it.

    What sort of insulation have they used in the roof? Is it the foil covered stuff?

    Do you have an en-suite in the loft conversion? If so, is the extractor fan connected properly? (thought it was worth asking)

    You may want to have a gander at this video, it certainly helped me understand my own flat roof.
     
  6. linzey123

    linzey123 New Member

    They seem to have built it with beams running back of the house to front so assuming that air would flow from soffits up to the ridge vent. The mushroom vents have since been added in the middle. I do not think there is any cross ventilation. Assuming if I take the ceiling down this could be rectified without taking the roof off?

    They used foil backed sheet insulation however they have left gaps for spot lights which I have now learnt is a big no, no! Can I ask should this element have been checked by building inspector before sign off….as this seems like a standard thing that should NOT be done from what I have read and I am wondering if they have therefore broken Building regulation rules?

    Yes we have an en-suite with extractor and we don’t seem to have a major issue this side but this may be because this is close to the ridge vents…
     
  7. AnotherTopJob

    AnotherTopJob Screwfix Select

    How many ridge vents are there? When we had a dormer conversion about 5 years ago they replaced all the ridge tiles with a dry system which apparently aids ventilation.
    (I am not a roofer BTW so hopefully someone qualified will clarify).
     
  8. linzey123

    linzey123 New Member

    I believe that we have something like this too.
     
  9. doesitmatter

    doesitmatter New Member

    Couldnt give you advice about the roof vents and roof being taken off. Sorry.

    Loft conversions are permitted development, so subject to Building Regs sign off. As part of Building Regs, they will be looking at Parts B (Fire Safety) and P (Electrical Safety).
    I am not an inspector but gaps for spot lights compromise thermal continuity, so would likely not be signed off if spotted.

    I only asked about the en-suite as I have noticed condensation dripping above my ducting out of the extractor (even though I havent used the shower, only the extractor) and have read that it could be an issue with the design, so have bought a vented roof tile to reduce the ducting run; which sits opposite a flat roof. Though my loft isnt converted, I have installed a lot more insulation up there (300mm) and it has clearly a fine balance I need to think about.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice