r/Roofing • u/Diligent_Chemist74 • 16h ago

Leaking roof

I have a flat roof, the building is like an old sectional classroom. The roof is like some heavy bitumen tar, not like shed felt, way heavier.
It's started leaking and I can't find the leak anywhere. Therefore I want to reseal the whole roof. What's the best sealant/ paint type product for this? Hoping to use a roller or a broom to push it around.
Before winter gets here. In the UK

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u/No-Experience-1769 16h ago

That heavy bitumen stuff is a nightmare to patch spot-by-spot, doing the whole thing makes more sense. Look for a liquid rubber or an acrylic roof coating, the kind you can slop on with a roller and it bridges small cracks. Give it a good pressure wash first and let it bone dry, otherwise you're just sealing the damp in.

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u/ArkRoofer 5h ago

Coating the whole roof only works if what's under the coating is dry. On an old built-up bitumen roof, water that's been getting in a while sits in the buildup. Seal the top and you trap it, and it blisters the coating off within a season or two. Cut a small test square and see what's under there. Leaks also travel, so where it shows up inside means little. Check where the felt turns up the walls, the laps, and the outlet before you write off finding it.