Breathable felt not weatherproof.

Discussion in 'Builders' Talk' started by Breathable felt not weatherproof, Jan 10, 2006.

  1. I've used Permavent breathable sarking felt, laid over rafters with a 6" gap between battens and good sized overlaps. The roof pitch is over 35 deg and all is well nailed with a dip in the felt - my own roof so I've been extra careful.
    In all the literature it states that the felt provides a weatherproof temporary covering, but it doesn't. There's a lot of leakage and dripping where the battens are nailed over the felt, as if the pinched area between batten and rafter lets the water soak through.
    Is this a common problem ? I realize that once the slating is completed there should be no leaks, but it's worrying to stand in the roofspace and be surrounded by drips !!
    Anyone else had similar experiences ?
     
  2. NAF

    NAF Member

    You must have made an error somewhere. Remove all the battens and membrane and start again ....

    only joking! I've had the same experience as you described, and consoled myself with the fact that one the tiles are on it will be waterproof, wont it ....?
     
  3. ­

    ­ New Member

    To be honest I've never seen rainwater dripping through a felt and battened roof prior to tiling.

    If the felt sags a bit between the rafters (as you say) then how does the rain find the nail holes on the rafters? There will be some rain run down the rafters but this should not find its way in through the nail head, definately not enough for you to be 'surrounded by drips'

    I don't follow your comment about the 6" gap between the battens? You should have a vertical batten on each rafter then cross battened to suit the tile gauge OR use 25mm thick battens horizontally with no vertical counter battens. So where's this 6" battening you mention?
     
  4. Hi.
    Thanks for your reply. I have used traditional cross battening with 6" spacing to suit the slate size. I have not used a vertical counter batten. The felt does dip by the recommended ammount and it really does drip badly where the battens are nailed.
    I think with bitumen felt the batten gives a good seal due to it being soft and fairly thick.
    Can't see anything I've done wrong - it's all nailed down tight and looks tidy, with correct lapping.
     
  5. 4 x 2

    4 x 2 New Member

    no nor i ,until i started usig breathable felt
     
  6. Roofer

    Roofer New Member

    I've experienced this once before and Sod's Law meant it was on a domestic re-roof.
    Realised that it occurred in rainy and windy weather.
    The underlay was being lifted up by the wind and the water was being pushed to the batten/rafter join, capillary action was then drawing it under and into the nail hole.
    There was no further problem once the roof was tiled.
     
  7. John coulter

    John coulter New Member

    Same here. I've done numerous roof jobs, no problem using sparking felt. I've been doing my own extension at home and like always when you're working and trying to work at home too, much to my wife's dismay, the customer always comes first. The slates have not been laid, the roof is leaking badly and getting worse. I'm torn between slating it, knowing that it won't leak when the slates are on, but then,what was the point of felting in the first place?
     
  8. John coulter

    John coulter New Member

    Ha ha. Sparking felt? SARKING FELT!
     

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