Fix roofing felt - which sealant?

I have a split in the garage roof about a foot long which is letting water into the fibreboard below.  At the moment that fibreboard is soaking wet but I suspect if I stop the water getting in that will probably dry out eventually froom the inside.  I have a new piece of felt, albeit a bit thin, which will cover the split but questions is what sealant/adhesive is best to fix this on with and make it waterproof?  I have seen some BlackJack Bitumen Felt Adhesive but that says it must be applied dry and there is no way that split is going to dry out until I stop the water getting in.  Also seen some Bituminous Mastic which says it is for waterproofing.  Any suggestions?

Comments

  • grumbler
    grumbler Posts: 58,629 Forumite
    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    edited 20 May 2023 at 7:22PM
    How big is the 'split'?
    The existing felt dries fast. Glue the patch to the felt, not the board.
    If you want to glue it to the board as well, you can try hybrid polymer sealants that apparently can be used for wet surfaces too.
  • RomfordNavy
    RomfordNavy Posts: 762 Forumite
    Part of the Furniture 500 Posts Name Dropper Combo Breaker
    grumbler said:
    How big is the 'split'?
    The existing felt dries fast. Glue the patch to the felt, not the board.
    If you want to glue it to the board as well, you can try hybrid polymer sealants that apparently can be used for wet surfaces too.
    About 12" long.  If you squeze the crack you can see that there is moisture in the board underneath.

  • TELLIT01
    TELLIT01 Posts: 17,866 Forumite
    Tenth Anniversary 10,000 Posts Name Dropper PPI Party Pooper
    When I had a tear in the roofing felt on my shed roof I used self adhesive flashing material.  https://www.screwfix.com/p/bostik-flashband-grey-10m-x-100mm/57969

  • RomfordNavy
    RomfordNavy Posts: 762 Forumite
    Part of the Furniture 500 Posts Name Dropper Combo Breaker
    edited 22 May 2023 at 4:10PM
    In the end I used this stuff in the crack and to bond a new bit of felt on top.  Just waiting for it to rain to see if it has sealed.
    <code><a rel="nofollow">https://www.selcobw.com/trowel-mastic-blac</a><a rel="nofollow">k<br></a>

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