Description

Controlling fire spread between residential buildings and outbuildings is important for protecting life and property. We recap the requirements and look at an area of confusion – fire rating of windows and doors in walls close to a boundary.

BRANZ HELPLINE calls suggest that misunderstandings remain about the fire resistance rating (FRR) requirements for walls less than 1 m distance from the boundary but at an angle of 90° or greater to the boundary.

This article updates and builds on previous articles in Build 141 External fire spread on houses and Build 158 External fire spread between buildings. These addressed external spread of fire between buildings and the change to Building Code Acceptable Solution C/AS1 in 2017 to include a notional boundary between two buildings on the same property under a single land title if they contain sleeping risk groups.

Scope

This article includes:

• Acceptable Solution C/AS1
• Sprinklers change external wall requirements
• Check walls under 1 m from boundary
• Windows and doors
• Multi-unit dwellings
• Protecting eaves
• Attached buildings
• Exterior surface finish requirements
• No FRR needed for some open structures
• Select notional boundary that works best
• Treat alteration work as a new build
• Cannot simply replace windows like for like
• An alternative is to add more light
• The topic is a complex one