NCC 2025 Volume One F1D3 (Class 2 to 9); Volume Two H2D6(1)(a) (Class 1 and 10) · AS/NZS 3500.3:2025 Clause 3.4 (catchment area)
Under NCC 2025, stormwater drainage for Class 2 to 9 buildings is designed to AS/NZS 3500.3 (Volume One F1D3), and AS/NZS 3500.3 is a Deemed-to-Satisfy route for gutters and downpipes on Class 1 and 10 buildings (Volume Two H2D6(1)(a)); this calculator applies its Clause 3.4 catchment.