Notes for single-storey detached buildings: 2.1 to 2.5
When planning your build you’ll need to consider a range of factors, including the local District Plan, where the building will be located, and what services can be included. There are five exemptions for single-storey detached buildings.
Sections 2.1 to 2.5 cover 5 separate exemptions for single-storey detached buildings.
- Buildings not exceeding 10 square metres in floor area.
- Single-storey detached buildings exceeding 10 but not exceeding 30 square metres in floor area, constructed of lightweight materials.
- Buildings exceeding 10 but not exceeding 30 square metres in floor area using a kitset or prefabricated building where a manufacturer or supplier has had the design carried out or reviewed by a Chartered Professional Engineer.
- Buildings not exceeding 30 square metres in floor area where a Licensed Building Practitioner is to carry out or supervise design and construction.
- Unoccupied detached buildings.
Before you begin your project, consider the following
District planning
Always check with your local council to make sure your proposed building work does not have any district or regional planning implications taking consideration of maximum site coverage, yard or setback requirements, daylight access planes or permitted activities. A resource consent may be required and it is important that this is obtained before starting any building work.
Plumbing
Any buildings that include plumbing cannot be built using these exemptions. A building consent is required.
Durability
The Building Code requires building materials, components and construction methods to be sufficiently durable to ensure the building (without reconstruction or major renovation) satisfies the other functional requirements of the Building Code for the life of the building.
Smoke alarms
You must install smoke alarms if the detached building is going to be used for sleeping.
For more information on the location and type of smoke alarms to install, refer to NZS 4514:2021 Interconnected smoke alarms for houses — standards.govt.nz.
Any smoke alarm in a sleepout should be interconnected with the smoke alarms in the main dwelling.
Stormwater
You need to consider the Building Code requirements regarding the disposal of stormwater from the roof of your building. You should seek professional guidance and seek approval from your council. All new drains must be laid by an Authorised Drainlayer.
On-site waste water disposal systems
If the building is intended to be a sleepout in connection with an existing dwelling, and the waste water from the existing dwelling discharges to an on-site waste water disposal system (such as a septic tank), you need to check that the existing waste water disposal system has the capacity for the extra persons.
Location of services
You need to confirm the location of any underground services that could affect the location of the build. Check with your local council and an underground services location company to ensure you are not building over any existing below ground services, such as drains, electricity, gas and telecommunications.
Building close to boundaries
For the buildings described in this section to be exempt from needing a building consent, they need to be more than the measure of their own height (H) away from any other buildings or the relevant boundary of the property. If your proposed building will be closer than this, then you will need a building consent.
If you are building close to boundaries or other buildings, you need to consider the Building Code requirements regarding protection from fire, particularly in relation to the external spread of fire to neighbouring property and buildings.
Measuring the net floor area
The net floor area in a building is measured to the inside of the enclosing walls or posts/columns.
Note for manufacturers of prefabricated buildings
If you are a supplier or manufacturer of proprietary garden sheds, greenhouses, cabins or sleepouts, you should make sure anyone buying them is aware of the how the small building is to be used and located to be exempt from needing a building consent. If a small building is not used or located as required by the exemption, the purchaser will need to apply for a building consent.
Foundations
The foundations of the building must transfer and distribute the load to the ground securely and prevent uplift. The cited Standards within B1/AS1 such as NZS 3604:2011 set out some technical information for several building code compliant solutions. Homeowners are encouraged to seek professional advice if they are unsure if the ground can provide adequate support to the foundation.
NZS 3604:2011 Timber-framed buildings — standards.govt.nz
Constructing a sleepout that does not require building consent
MBIE and BRANZ have collaborated to produce a new guide, Constructing a sleepout that does not require building consent. It helps homeowners see if they need advice from a building professional or employ a building professional to do the work for them.
Constructing a sleepout that does not require building consent - guide [PDF 9.1MB]
This guide covers the building consent exemption for designing and constructing a single-storey detached sleepout with a 10–30 m2 floor area, which is built with lightweight materials. The example could be adapted for use with some other types of small buildings that are covered below and by the exemption in Part 3, Schedule 1 of the Building Act.