All spouting is subject to expansion, and therefore, there is a maximum recommended length before an expansion joint is needed. The maximum length is determined by the metal, its thickness, and colour. It is similar to the limit recommendations for roof cladding but should not exceed 12 m.

Spouting Support Systems

The spouting bracket system must withstand the potential weight of a gutter full of water. Bracket spacing is dependent on the spouting size, water flow and capacity.

Brackets should be made using compatible material or non-ferrous metal. Brackets for pre-painted external spouting should be painted or powder-coated before installation.

Brackets for external spouting should be located close to all stop-ends, at both ends of sumps and rain-heads, at a maximum of 750 mm spacing for gutters less than 180 mm wide and at 600 mm for gutters 180 – 300 mm wide. Brackets must be installed to provide a 1:500 (2 mm per metre) minimum gutter gradient towards the outlets.

Gutter Fall

All spouting must have a minimum fall of 1:500 (2mm in 1 m). Ace recommends 1:200 (5mm in 1m), as it will improve drainage and self-cleaning.

Graph — Onehunga, Auckland — Ace Spouting & Fascia

Rainfall Intensity

Rainfall intensity can be taken off the maps for 50-year average return intervals (ARI). When the co-ordinates of a site are known, site-specific values can be obtained using NIWA’s HIRDS tool at https://hirds.niwa.co.nz/

Capacity Calculations

Calculating drainage capacities of spouting, downpipes, and valleys involves various factors such as rainfall intensity, roof pitch, gutter size, downpipe size, valley angle, etc. The NZMRM Code of Practice (COP) provides online calculators to derive the maximum allowable roof area drained under various scenarios.

Calculating drainage capacities of spouting, downpipes, and valleys involves various factors such as rainfall intensity, roof pitch, gutter size, downpipe size, valley angle, etc. Refer to NZMRM COP, which provides online calculators to derive the maximum allowable roof area drained under various scenarios.

Ace Spouting Profiles

Formal Sketch — Onehunga, Auckland — Ace Spouting & Fascia

Downpipes

Standard steel downpipes for round 80mm and 100mm diameter or custom made in a rectangular shape such as 100mm x 55mm, in pre-painted coil steel of ColorCote® (Zinacore, Magnaflow, Alumigard) and/or Colorsteel (Zincalume, Endura, Maxx). The placement of downpipes significantly affects gutter and downpipe calculations.