Bitumen
A viscous petroleum-derived binder, the base material of most sheet waterproofing membranes and of traditional built-up roofing.
On an actual building
It is waterproof, adheres well when hot, and is inexpensive. Its weakness is temperature sensitivity: it softens in heat and embrittles in cold, which is why modern membranes modify it with APP or SBS polymers.
What we most often have to correct
That exposed bitumen lasts indefinitely. Ultraviolet light oxidises it, which is why exposed sheets need a mineral finish or a protective screed.
Terms that come up alongside this one
- APP Membrane
Atactic-polypropylene-modified bitumen sheet, torch-applied to a primed substrate with lapped and sealed joints.
- SBS Membrane
Styrene-butadiene-styrene-modified bitumen sheet.
- Primer
A preparatory coat applied to a substrate to seal it, improve adhesion and provide a compatible surface for the system that follows..
Bitumen — questions we get asked
What does bitumen mean in waterproofing?
A viscous petroleum-derived binder, the base material of most sheet waterproofing membranes and of traditional built-up roofing.
Why does bitumen matter on a real project?
It is waterproof, adheres well when hot, and is inexpensive. Its weakness is temperature sensitivity: it softens in heat and embrittles in cold, which is why modern membranes modify it with APP or SBS polymers.
What do people commonly get wrong about bitumen?
That exposed bitumen lasts indefinitely. Ultraviolet light oxidises it, which is why exposed sheets need a mineral finish or a protective screed.
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