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FLAT ROOF - ONE LAYER OF FELT?

Discussion in 'Roofing and Guttering' started by artfuldodger128, 10 Feb 2008.

  1. artfuldodger128

    artfuldodger128

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    I am planning to replace my existing flat roof.

    I bought this Protect A1 underlay sheet from screwfix which claims to be better than traditional felt underlay. The plan is to lay a sheet of this stuff (instead of the normal 2 layers of underlay) and have a capsheet on top.

    Will this work?

    Further, I am also very wary of moisture coming through over time. Would it be possible to place a damp-proof membrane underneath the capsheet using felt adhesive?

    Any advice will be appreciated.
     
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  3. Deluks

    Deluks

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    Keep your receipt! I believe the A1 is meant to go under tiles on a pitched roof. AFAIK screwfix don't sell any flat roofing materials.

    Felt adhesive should only be used on felt, a good quality felt is what's needed, and ideally 3 layers. How big an area do you have to cover?
     
  4. artfuldodger128

    artfuldodger128

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    Many thanks for the response.

    The flat roof is about 2m x 2m. The reason I am looking for alternatives is that I dont feel felt will last. I had a guy who did some work on the same flat roof about 3yrs ago, and water has penetrated onto the board and now I have to replace the whole lot! And I paid a lot of money for it as well!

    Are there alternatives other than felt?

    Also, can you respond on the point I had on the damp proof membrane? Cheers.
     
  5. ^woody^

    ^woody^

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    Felt, done properly should last more than 10 and up to 25 years in the right place.

    Bitumen felt is a layer system. One layer is bonded to the deck and then another one or two laid on that. You can't fit a DPM on the deck first, and there is no advantage in it in any case.

    Water does not penetrate felt over time. It gets in if a joint opens, or the felt is punctured.

    Don't let that cowboy job put you off felt. Done right, it will last.

    And alternative is rubber/epdm cover. Lots of posts on here about it
     
  6. datarebal

    datarebal

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    2 mtr x 2mtr should not have cost much.. certainly not worth faffing around with cold adhesives etc
     
  7. use torch on felt, you can get 2mm underlay then a layer of 4mm torch on cap sheet on top, the felt itself is a form of damproof membrane. be careful when using a cas torch.
     
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