Dwellings with family flats/minor residential buildings
Considerations for designers and owners
If you are thinking of building a dwelling that is not a single household detached building you need to be aware of the rules and requirements covered below.
Family flat and minor residential buildings defined
Historically family flats and minor residential buildings were often separate small buildings sharing the same property lot and services occupied by a family member.
Now they are often included as a separate part or wing of the main house.
They are:
- Characterised as spaces with cooking, bathing sleeping and living areas that can be lived in independent of the main house
- Named either a family flat, accommodation unit, studio, self-contained area, or separate tenancy, etc.
In the District Plan they are
- family flats under the current plan, or
- minor residential units under the proposed new plan which is currently under consultation and not yet operative.
This guidance will call them family flats for simplicity.
Not included under this guidance are
- other attached dwellings (eg adjoined houses on separate property lots with individual titles such as townhouses), or
- buildings on a single lot (eg unit titles such as apartments and retirement villages),
which also need to meet different or additional design requirements to those of a single detached dwelling on a single property lot.
How family flats are defined by the district plan
Current plan definition | Proposed plan definitions |
|---|---|
Dwelling: means any building or buildings or any part of a building or buildings which is used as a self-contained area for accommodation or residence by one or more persons; where that area collectively contains: bathroom facilities, kitchen facilities and a sleeping/living area. The term dwelling includes a family flat up to 70m2, except where the Plan has separate provisions that apply specifically to family flats. Where any buildings, building or part of a building on a site contains more than one set of bathroom facilities, kitchen facilities and a sleeping/living area such that they can be used as self-contained residences by different households, then each separate set of facilities shall be deemed to be one dwelling. | Residential unit means a building(s) or part of a building that is used for residential activity exclusively by one household, and must include sleeping, cooking, bathing and toilet facilities. |
Family Flat: means any dwelling up to 70m2 in gross floor area, excluding garaging, which is located on the same site as an existing dwelling and the family flat is occupied by a member of the same immediate family as a person residing in the main dwelling on the site. A family flat may be attached to either the dwelling or an accessory building, or be free-standing. | Minor residential unit means a self-contained residential unit that is ancillary to the principal residential unit, and is held in common ownership with the principal residential unit on the same site. |
District plan rules that apply to family flats
| Current plan | Proposed plan |
|---|---|
4.6 BUILDING AND BUILDING DENSITY Permitted Activities – Buildings and Building Density 4.6.1 The erection on an allotment (other than a site at Castle Hill) or not more than either:
| Activity status: PER
Where a. no more than one residential unit or other principal building is established on the site. And this activity complies with the following rule requirements:
|
Under the current District Plan where a building like a family flat is proposed to be not occupied by family a separate resource consent application is required. | GRZ-3 Minor Residential Unit Activity status: PER
Where:
|
Other considerations
Council services requirements which are incorporated in district plan
| Single dwelling | Family flat | Minor residential unit |
|---|---|---|
Individual water, sewer and connection to street or easement | Shared with main dwelling | Shared with principle unit |
Individual entrance driveway | Shared with main dwelling | Shared with principle unit |
Individual electricity and communications connections to street or easement | Shared with main dwelling | Shared with principle unit |
Rates
To understand how a family flat or minor residential unit will affect your rates see the interpretation under Council’s rating policy:
- Separately used or inhabited part of the rating unit (SUIP) means any part of a rating unit separately used or inhabited by the ratepayer, or by any other person, having a right to use or inhabit that part by virtue of a tenancy, lease licence, or other agreement, or any part of parts of a rating unit that are used or occupied by the ratepayer for more than one single use. Separately used or inhabited parts include:
- a residential, small holdings, or farmland property that contains two or more separately occupiable units, flats or houses each of which is separately inhabited or is capable of separate inhabitation, ie has independent kitchen facilities.
If you’d like an estimate you can contact our rates team on 0800 SELWYN or contactus@selwyn.govt.nz.
Development contributions
Any second dwelling or family flat triggers the requirement for development contribution under the current development contribution policy.
An assessment for development contributions allows for discount factors to be applied dependant on the size of the dwelling being built, if it is attached to the main dwelling and/or the size of the underlying land parcel that it is being built on.
Development contributions need to be paid and received in full before the code compliance certificate will be issued.
If you would like to be provided with an estimate for your proposed development please email development.contributions@selwyn.govt.nz.
Building Act and Code
All buildings have a use of building group for the purpose of applying the requirements of the building act or building code.
This classified use is noted on a building consent application.
Classified use – Building code A1
| Single dwelling | Family flat | Minor residential unit | |
|---|---|---|---|
| Within one building | Detached dwelling | Multi unit dwelling | Multi unit dwelling |
| Separated/detached | Detached dwelling | Detached dwelling |
Use of building group
| Single dwelling | Family flat | Minor residential unit | |
|---|---|---|---|
| Within one building | SH | SR | SR |
| Separated/detached | SH | SH |
What this means
- There are less requirements for detached dwellings which are SH (sleeping single homes)
- More requirements apply for family flats (or minor residential units) which have a use of SR (sleeping residential) – general due to having two household units
When council reviews a buildings for compliance, the Ministry of Business, Innovation and Employment (MBIE) advice is to determine the use of the building based on how the building is proposed to be used. This includes considering any other future use that is reasonable to foresee that the building could be used for.
In most cases it is therefore reasonable to anticipate that today‘s dwelling with a family flat could, with little modification, become the homes of two independent households.
What to consider for family flats
- Most family flats will need to take into account with their design sound separations where habitable spaces are next to each other (see building code G6)
- Fire separation needs to be taken into account when
- the external walls or roof of separate dwellings and family flats are too close together (refer C/AS1 Part 5.1.1(a) and 5.1.2) – for more information see the BRANZ publication on boundary wall fire resistance rating, or
- the family flat is attached or within the main dwelling (as required by C/AS1 Part 4.1).Where the buildings are joined, fire walls usually extend from the base of the building to the underside of the roof to divide the building into two separate fire cells. The walls can be made from
- tested fire rated construction methods, typically using sheet material specified by manufacturers in their technical literature, or
- some masonry construction products.
In certain cases ceilings are also fire rated.
Where a family flat shares spaces with the main dwelling (eg garages or laundry) these are generally still considered to be two household units. The fire separation location will typically follow the walls of the family flat with any shared spaces usually included within the main dwelling.
The benefits of internal firewall are shown in the fire separation in domestic houses publication by Fire and Emergency New Zealand (FENZ).