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Rooftop PU waterproofing: primer, body coats, topcoat—and DIY limits

PU roof waterproofing is not one brush coat. Primer, 2–3 body coats and a UV topcoat, plus detailing at parapets and drains, make a complete system. Know what you can DIY.

Why a single coat fails

No primer: poor bond, sheet peels
One coat only: too thin, ages and cracks fast
No detailing: outlets and parapet corners leak first
Dirty substrate: dust and oil kill adhesion

Three main coats

Detailing that decides success

Reference workflow

Clean roof; remove moss and oil
Fill small cracks; treat large cracks first
Confirm dry substrate
Primer
Detail reinforcement
Body coats 2–3 with drying intervals
Topcoat
Ponding test 24–48 hours

DIY limits

When not to DIY

FAQ

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