health risks

There are potential health risks associated with moulds and other fungi that can grow in a damp building.

When dealing with leaking buildings, the potential for finding mould in wall cavities is very high, and it is important that the proper precautions are taken to ensure that neither workers nor building occupants are exposed to health hazards from moulds during building repairs.

Maintenance and repairs

New Zealand is one of the few countries in the world that requires buildings and building components to last for specified minimum periods of time as part of legislation. Find out about the New Zealand Building Code.

As a building professional, you may be approached to undertake an assessment on, design repairs to, or undertake repairs on a leaky building.

While repairing a leaky building has some similarities to renovating or adding on existing buildings, there are some significant differences.

Schedule 1 under the Building Act 2004, generally allows like for like replacement of cladding materials without the need for a building consent.

However, situations where the cladding has failed to meet the minimum durability requirements (generally 15 years for claddings) before leaking are specifically excluded except where the repair is maintenance. Normal maintenance is that work generally recognised as necessary to achieve the expected durability of a given building element.


Before any repair options can be considered, a thorough investigation must be carried out to identify the causes of any leaks and the extent of any damage to the building, particularly timber framing, flooring and linings.

Assessing leaky buildings is a specialised profession and requires the right training, equipment and experience. In addition an assessor should carry insurance. An assessment report may be available on an individual home if the owner has commissioned an investigation, or one may have been generated under the Weathertight Homes Resolution Services Act 2006.

Information on companies who specialise in assessing leaky homes is available online [External link].

Designing Repairs

Once the state of the building has been assessed, design of repairs can be considered.

Differences between design for repair of leaky buildings and other design work include:

  • Substantial uncertainty around the amount of damage that may be found when construction starts and the need for variations to consents to deal with this
  • Need for higher contingencies
  • Consideration of value -add opportunities beyond minimum repairs (betterment)
  • Nature of owners circumstances and potentially litigious environment
  • Deciding what is an appropriate repair strategy.

See the guidance on Weathertightness: Guide to remediation design »

Carrying out repairs

Once a repair design has been completed, the design can be put out to tender.

Differences between repair of leaky buildings and other building work include:

  • Substantial uncertainty around the amount of damage and variations to costs that may become obvious when repairs are started
  • Health and safety issues with mould and fungi
  • Scheduling work and potentially working around occupants

The guidance documents are on assessing leaky buildings and designing repairs to leaky buildings will help inform builders of issues to be addressed when repairing leaky buildings.

Read the Dealing with timber in leaky buildings guide »

Normal maintenance

Secondary building elements can meet their minimum durability requirements with the help of what is termed ’normal maintenance’ of the material or system. Normal maintenance is that work generally recognised as necessary to achieve the expected durability of a given building element. It is the responsibility of the person specifying the building element to determine the normal maintenance requirements and to nominate them on the plans and specifications submitted for building consent.

Scheduled maintenance

Commercial buildings that have systems affecting the health and safety of occupants are required to have those systems regularly checked for on-going compliance. Compliance schedules are determined as part of the building consent process and used for the issuing of annual building warrants of fitness.

Appropriate maintenance

For maintenance to be effective, it must be appropriate and able to be carried out. Materials used in places difficult to access that require frequent maintenance may be quite unsuitable. Therefore, it is necessary for designers to choose materials and systems that are appropriate to their application and use, and to clearly nominate what maintenance is required to keep them code compliant. Only when this is specified does the owner and any subsequent owner know what is necessary to ensure the material will be sufficiently durable.

For further descriptions of what is meant by maintenance, see paragraph 2.0 of B2/AS1 (B2 Durability).

You can also find information on maintenance and repairs on our ConsumerBuild [External website] website.