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Breathable membrane

Discussion in 'Roofing and Guttering' started by Bob49, 6 Sep 2018.

  1. Bob49

    Bob49

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    Hello,

    While cleaning out my gutters the other day, just after it had rained, I noticed that the end of my breathable membrane was saturated. I can't see a lot of it, but because I have double roman tiles you can see between the raised parts of the tile. The roof is not leaking, its just the angle of the rain hitting the membrane. Also like the majority of roofs I don't have any eaves protectors.

    At the time I didn't think much of it, but thinking about it later it occurred to me that if the membrane can soak up water then couldn't it soak water back far enough to get beyond the fascia board and affect the timbers?

    So yesterday when the membrane was dry I poured some water on the edge of it with a watering can and it does indeed soak up water. You could see the water creeping up the membrane.

    So my question is, isn't this bad? Can it really soak water back far enough to cause problems? Is this a known issue with breathable membranes?

    Something seems wrong here to me.

    Any thoughts most appreciated.


    Thanks,

    Bob
     
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  3. Bob49

    Bob49

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    I've just thought that maybe as the ends of the membrane have been exposed for 7 years then that has something to do with it? Maybe UV damaged or something?
     
  4. ^woody^

    ^woody^

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    Membrane should not be exposed and should not be in the gutter - there should be a plastic eaves tray there instead with the membrane cut under the eaves tile where it is protected.

    Membrane will absorb water on the back surface due to the fleece material, thats how it works and is nothing to to with age.

    The memabrane will be degraded by UV and will rot at the gutter leading to water eventually running down the fascia and wall and not into the gutter
     
  5. Makie

    Makie

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    Just to add to this you can get felt that is made to go into the gutter, we use 5U felt regularly in Scotland
     
  6. ^woody^

    ^woody^

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    That's the same concept - a specific eaves product that is UV stable - its not felt in the sense of roof felt for the whole roof. Effectively a roll of modified bitumen DPC.

    It's used here too, but some cheapskates use the cheap polythene DPC instead. If the homeowner can't see it, they certainly hear it every time the wind blows
     
  7. Bob49

    Bob49

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    Thanks woody, yes I agree eaves tray are the correct way to do it. But I see plenty of roofs where the membrane finishes just after the tiles with no eaves protectors.

    If as you say the back surface of the membrane is absorbent then is it not possible for water to be absorbed back up beyond the soffit, therefore coming into contact with the timbers?
     
  8. ^woody^

    ^woody^

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    No doubt, but it's not correct. And what homeowner checks, or even knows what is correct?

    Whilst membrane is technically absorbent on one side, it's not to the extent so as to cause the situation that you mention.
     
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