Changing the use of a room or building

Renovations sometimes involve changing the use of a room or even a whole building. A space once used for storage may become another bedroom, a commercial building may be converted to a residential dwelling, or a large shed may be converted into a self-contained rental flat. In cases like these there are special requirements to be aware of and it can be a complicated process. It’s a good idea to consult with your local council from the very early planning stages of the project to check just what their requirements are.

Every building is designed for a specific use and has to meet Building Code requirements that ensure it will be safe, healthy and durable when used in the way it was designed. If that use changes, the building may need to be altered to support the new use.

Changing one space in a house

When households need more space, a basement, a garage or storage area may be converted to a bedroom. This may be less costly than extending the house, but not always – excavating under a home to create a new room will often be more expensive than building a new room at ground level, for example.

Creating a bedroom from another space in a house is not defined as “change of use” under the Building Act (the next section explains this in more detail), so those requirements do not apply.

Some of the work involved in a conversion may require a building consent. Installing a small wet bathroom or retrofitting thermal insulation to an external wall both require consent, for example. Any work that involves load-bearing walls and bracing will also require professional input from a chartered professional engineer, architecture designer, or similar.

Simple, lower-risk work does not require building consent – installing a small window in an outside wall, removing or adding a section of non-loadbearing wall, adding plasterboard linings to ceiling and walls. Councils can provide more advice. There are also resources online, including a government publication Building work that does not require a building consent.

Remember that even when a building consent is not required, all work must still comply with the Building Act and the Building Code. Work must not make a building perform worse than it did before the work was started.

Changing the use of a building

Different rules apply when it comes to changing the use of a whole building. Under the Building Act (Section 114), a building owner must give written notice to the territorial authority (TA) if they plan to change the use of a building. They can only go ahead with the change after the TA gives written notice that it is satisfied that the new use of the building will comply with the Building Code (Section 115). There are broader compliance requirements where non-residential buildings are being converted to household units.

There are also significant compliance requirements if construction/alteration work is being done to convert, say, a large private house into a facility which members of the public will use, such as medical chambers. In this case, the Building Act requires access, parking provisions and toilet facilities for people with disabilities (Section 118). 

What constitutes a “change of use” depends on whether the old and new uses are in the same use category in Schedule 2 of the Building (Specified Systems, Change the Use, and Earthquake-prone Buildings) Regulations 2005. If old and new uses are in the same category, there is no change of use. If they are in different use categories and Building Code requirements for the new use are higher, then the use is changing and the council must be informed before work begins. (The council must be informed in writing of a change of use in a building even if no building work is being carried out.) If you make the change without advising the council you could be liable for a fine of up to $5,000.

A change of use itself does not automatically require a building consent, but you will need to apply for building consent if you will be carrying out building work that requires a consent. Councils have the discretion to exempt work from needing a building consent based on their assessment of the risks involved.

In some cases, resource consent may also be required, for example where part of a property is being converted to a self-contained rental unit that includes a kitchen.

Here are some examples of working out whether something is a change of use or not:

• Where a large single house is being converted into three dwelling units, section 115(b) of the Building Act applies. This is a category change, from the “sleeping single home” to “sleeping residential” category. It is a change of use because there are tougher Building Code requirements in the new use, for example around dealing with internal moisture and fire protection. (If the building is two or more storeys and is being converted into three or more household units, it must also be assessed for its earthquake-proneness – Building Act clause 133AA(2).)
• A householder plans to launch a business as a sole trader and will use their garage as their workspace. This is not a change of use because the main use of the building still sits within the “sleeping single home” category.
• A house is going to be used as a childcare centre. This is a change of use because it is a category change (“sleeping single home” to “crowd small”) and the new use will normally require access and bathroom facilities for people with disabilities.
• A garage not connected to a house is being made into to a sleep-out for a family member. This is not a change of use as both old and new uses are within the same category of “sleeping single home”.

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