A retaining wall in a rural zone usually doesn't require a building consent if it's designed by a chartered professional engineer, and is further away from a legal boundary or building than its own height.
What the law says
Schedule 1 of the Building Act 2004 states the following:
1. Building work in connection with a retaining wall in a rural zone, if:
(a) the wall retains not more than 3 metres depth of ground; and
(b) the distance between the wall and any legal boundary or existing building is at least the height of the wall.
2. In subclause (1), rural zone means any zone or area (other than a rural residential area) that, in the district plan of the territorial authority in whose district the building work is to be undertaken, is described as a rural zone, rural resource area, or rural environment, or by words of similar meaning.
Guidance on the exemption
This exemption extends what is allowable without a building consent under exemption 20 – retaining walls.
It also exempts retaining walls designed or reviewed by a chartered professional engineer of up to 3 metres and in a rural zone as long as they are not too close from the boundary or existing buildings (refer to subclause (1)(b)).
This exemption recognises that in low density rural zones (eg on farms) the consequences of failure of any retaining wall are less likely to cause injury than they would be in higher density urban environments. The additional requirement for a chartered professional engineer to be involved also helps to make sure that retaining walls covered under this exemption are less likely to fail.
Note: If there is a fall of at least 1 metre, a safety barrier may be required under Building Code clause F4 – Safety from falling.
Examples where this exemption could apply
|Constructing a retaining wall on a rural property that is 2.5 metres high, 3 metres away from an existing dwelling, and is designed by a chartered professional engineer.|
|A farmer decides to rebuild an earthquake-damaged retaining wall on his rural property that is 3 metres high and located 6 metres away from a legal boundary. The wall design has been reviewed by a chartered professional engineer.|
Examples where building consent is required
|Constructing a retaining wall on a rural property with a height of 3 metres, 1 metre away from an existing dwelling and designed by a chartered professional engineer. A building consent is required because the wall is closer to the dwelling than its own height.|
|Constructing a retaining wall on a rural property that is 3 metres high and 5 metres away from the property boundary which has been designed by an engineer, but not a chartered professional engineer. Though the retaining wall is not located closer to a legal boundary than its own height, a building consent is required as the wall has not been designed or reviewed by a chartered professional engineer.|