Loose stone, river rock, or crushed slag applied as the top layer of a built-up or protected membrane roof. The rock provides ballast to hold the system down against wind uplift and protects the underlying asphalt and felts from ultraviolet degradation and physical damage.
Heard on the job
We need a crane to hoist the aggregate up to the plaza deck before the wind picks up.
Also heard as
- ballast
- river rock