Minimum Roof Cladding Pitch

Buildings designed with widely spaced purlins and widely spaced portal frames may require an increased design pitch to comply with the minimum recommended as-laid pitches.

Low-pitched roofs require greater attention to flashing details. The ability of side laps or end laps to withstand water penetration also becomes more critical at low pitches, but a good design of flashings can ensure weathertightness in extreme conditions.

A printable bulletin regarding re-roofing low pitched trough section roofs is available at: BSP01 Replacing Trough Section Roofs at a 1° Pitch.

Extract:

"Roof replacement with a “like with like” does not require a building consent (Exemptions Guidance for
Schedule 1 of the Building Act 2004, Fifth edition August 2020). An existing flat roof that has met the
performance requirements of E2—External Moisture, and B2—Durability, can be replaced with a
comparable product, without re-pitching the roof."

• Curved roofs, where, by design, the minimum pitch at the crest is always less than the prescribed minimum pitch. In these cases, the pitch at the eaves must comply with the profile’s minimum pitch, and the pitch at the upper end of a terminated arc must be a minimum of 3°.  (See Curved Roofs).
• The back curbs of penetration flashings where the minimum pitch is 1.5°. (See Penetrations).
• Reroofing trough section roofs at less 3°, where satisfies the requirements and considerations of Building work that does not require a building consent (Exemptions Guidance for Schedule 1 of the Building Act 2004) Fifth edition August 2020. More information is available at   Building work that does not require a building consent, Section 1.1 General repair, maintenance and replacement of building parts (page22).