Ballast
Ballast layer 50mm, weight minimum 80kg/m2.
A ballasted roof is a sustainable, low-maintenance and cost-effective flat roofing system where a loose-laid waterproof membrane is secured by a heavy top layer – typically gravel, stones or concrete pavers. This method protects the membrane from UV radiation and wind uplift, while providing excellent fire resistance.
Key Aspects of Ballasted Roofs
- Installation: Membranes are loose-laid rather than mechanically attached or glued, which often makes installation faster and less weather-dependent
- Ballast Types: Common materials include 20–40mm washed river stone (pebbles)
- Weight Requirements: The ballast layer must weigh at least 80kg/m2 to provide adequate wind uplift resistance
- Protection & Benefits: The ballast acts as a protective layer, significantly increasing the membrane’s lifespan and creating a “cool roof” that improves energy efficiency
