Fix roofing felt - which sealant?

RomfordNavy

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?

grumbler

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

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

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

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.

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