1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Pooling roof leaking

Discussion in 'Roofing and Guttering' started by RoofingMystery, 13 Oct 2018.

Tags:
  1. RoofingMystery

    RoofingMystery

    Joined:
    13 Oct 2018
    Messages:
    2
    Thanks Received:
    0
    Country:
    United Kingdom
    We're having a new roof built and in my opinion, there isn't enough pitch. This is partly proven in that the roof leaks and pools. The builder claims this is because the resin used (same as in boat hulls) needs 2 applications (so far only one has been applied) but that there is enough gradient.
    The pools now stay well over the rec. 48hrs unless temperatures rise or it's dry weather for several days. The only time it flows off the roof is when the pools reach saturation levels and spill over. If the wind blows from the west, the water collects in the NE corner and doesn't run off.


    We have another flat roof and I can clearly see water running in streaks off it, but not this new one. Am I being thick?
     

    Attached Files:

  2. Notch7

    Notch7

    Joined:
    15 Sep 2017
    Messages:
    10,680
    Thanks Received:
    917
    Location:
    Sussex
    Country:
    United Kingdom
    I aim for a fall of 1 in 40 to 1 in 60 for orangery flat roofs in grp. Ive never had an issue with ponding, just the odd small spot where the grp matting has bee n doubled up. A bit of localised ponding say a puddle of no more than 600mm round and upto 2mm deep, although not ideal, is probably of no practical issue. Approaching 5 to 10mm and that would constitute a build error.

    1 in 80 is the minimum theoretical and 1 in 40 is recommended for felt roofs to allow for variations like bowing joists and felt overlaps.

    I csnt see the final gel coat altering anything.

    Was there a reason not to have a decent fall? Sometimes height restrictions dictate a slightly less than ideal amount of fall. With no restrictions I would simply do a 1 in 40 -that gets over any overlap or sagging issues.
     
  3. RoofingMystery

    RoofingMystery

    Joined:
    13 Oct 2018
    Messages:
    2
    Thanks Received:
    0
    Country:
    United Kingdom
    No restriction that I know of. Even with the 'back' of the roof as low as it can go ie. flush with the roof tiles, there is plenty of space to drop the 'front' edge if it needed to be done. The GPR or resin is apparently used on boats but that's irrelevant since boats are designed (round) to withstand the hydrostatic pressure, while roofs are not. Although our pools may not be deep, they are all over the roof suggesting that there simply isn't enough pitch.
    I guess I just want to know if I'm barking up the wrong tree or if I'm right in suspecting a flaw in the pitch....;)
     
  4. catlad

    catlad

    Joined:
    29 Jul 2011
    Messages:
    3,473
    Thanks Received:
    459
    Location:
    Lancashire
    Country:
    United Kingdom
    Pitch of a roof is a fundamental to roofing?
    also if you know the roof isn't finished then why does it not have a temporary cover?
     
  5. catlad

    catlad

    Joined:
    29 Jul 2011
    Messages:
    3,473
    Thanks Received:
    459
    Location:
    Lancashire
    Country:
    United Kingdom
    I suspect the answer to both is can't be arsed.
     
  6. opps

    opps

    Joined:
    16 Jun 2006
    Messages:
    3,510
    Thanks Received:
    484
    Location:
    London
    Country:
    United Kingdom
    Why can't I see any fibreglass tape on the joins in the OSB?
     
  7. Notch7

    Notch7

    Joined:
    15 Sep 2017
    Messages:
    10,680
    Thanks Received:
    917
    Location:
    Sussex
    Country:
    United Kingdom
    The material is different to boat hulls, GRP on roofs is designed to have some flexibility.
     
  8. datarebal

    datarebal

    Joined:
    1 May 2007
    Messages:
    1,984
    Thanks Received:
    271
    Location:
    Hampshire
    Country:
    United Kingdom
    regardless of ponding it should not leak. but its obviously not finished
     
  9. Nick Pain

    Nick Pain

    Joined:
    12 Oct 2016
    Messages:
    23
    Thanks Received:
    1
    Location:
    Hertfordshire
    Country:
    United Kingdom
    Several things need investigating here....
    1. The roof should NOT leak at this stage. The second coloured coat with GRP protects the first from UV damage and while does strengthen the first coat, the first coat should be water proof in its own right.
    2. What is the piece of batten in the right of the first picture doing?
    3. Where is the flashing over the up-stand around the chimney?
    4. As lots of other people mentioned what is the slope?
    5. Were the joints between the OSB boards taped? Was T&G used or sheets? If sheets were the joints bandaged?
     
Loading...

Share This Page