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Does this stuff stick to damp surfaces?
https://www.toolstation.com/soudal-trade-roof-gutter-sealant/p34883
I have used this.
https://www.screwfix.com/p/bostik-roof-repair-compound-black-1kg/57518
Sticks to anything it touches, wet or dry. Fixed a gutter I had to seal.
You will need gloves and a brush, both with are a once use item. You will never ever be able to clean the brush.
Anytime i've used this stuff i clean the join beforehand with IPA, or even disc brake cleaner, and do it on a dry day.
The conservatory guys told me to use acrypol, they used it - clean area, try to dry area, apply.
CT1 claims to work in the wet and is a lot more useful for other jobs.
The non setting bitumen (?) stuff is horrifically easy to make a mess with, but does work.
I generally split the joint, use a cloth to clean and roughly dry it and apply, rather than just seal the gap.
I like to think the reason I don’t get called back is because it worked!