The Building Act 2004 (the Act) is one of the key legislations that manage natural hazards in relation to major building alterations and new constructions. The purpose of the natural hazards requirements under the Act is to protect building work, land other property from the effects of natural hazards by placing limits on the granting of building consents for building work undertaken on land that is subject to one or more natural hazards.

What are natural hazards?

The following are natural hazards under the Act:

• erosion (including coastal erosion, bank erosion, and sheet erosion):
• falling debris (including soil, rock, snow, and ice):
• subsidence
• inundation (including flooding, overland flow, storm surge, tidal effects, and ponding)
• slippage

Under this definition, geothermal events, volcanic events and earthquakes are not regarded as natural hazards and liquefaction is not a contemplated effect.

Some factors to consider for determining whether the building work is major alteration:

• The degree to which the proposed building work differs from building work that does not require a building consent (i.e. exempt building work. For MBIE’s guidance on exempt building work please see here). Building work for major alteration is likely to be significantly in nature and extent from exempt building work
• The intended use, degree of design and construction complexity
• The size of the alteration compared with that of the existing building
• The increased footprint of the building and the percentage increase in site coverage (please see the applicable council District Plan for site coverage requirements)
• Allowance for the replacement of existing structures with new building work
• The extent to which the performance of the building in question is likely to be affected by the natural hazard conditions

The above list of factors is not exhaustive. Also, it is unlikely a single factor will be determinative and the weight given to each factor will depend on the circumstances in question.

Building consents and natural hazards

Three scenarios can occur when a building consent for building work on land subject to natural hazards. They are outlined in the flowchart below.