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Internal Gutters

When internal gutters are difficult to replace and their failure could cause major disruption to the building below, they must be made from materials that will last 50 years to comply with the NZBC; metallic coated steel is not recommended for internal gutters that are difficult to replace.

Common internal gutter materials are butyl or other membranes, fibreglass, or non-ferrous metal. Where butyl gutters are used, the metal and flashings should be separated from wet contact with the butyl rubber.

Separation of Butyl Gutter and Metal Roofing

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Suitable non-ferrous metals include 0.9 mm aluminium, 0.6 mm stainless steel, and 0.6 mm copper. Contact between coated metal products and copper or stainless steel must be avoided because it will lead to early corrosion. Splashback or runoff from copper onto coated metal can have the same effect.

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