Retaining wall consent in NZ: the rules a landscaper needs to quote right

The 1.5 m rule and what it really says

Under Schedule 1 of the Building Act 2004, clause 20 exempts a retaining wall from building consent only when both conditions hold: it retains no more than 1.5 m depth of ground, and it supports no surcharge or load beyond that ground, such as vehicles. Both parts matter. A 1.2 m wall under a driveway is not exempt, because a car parked above it is a surcharge. A 1.4 m wall that holds back a sloping bank is also worth a second look, since sloping ground above the wall adds load. Height is measured as the depth of ground retained, from the low side to the high side, not the height of the posts you can see. Two stepped walls need particular care because the upper wall can load the lower. Drainage behind the wall is good practice and every competent builder does it, but it is not a condition of the exemption. An exempt wall still has to comply with the Building Code, so “no consent needed” never means “no standards apply”.

The rural exemption: up to 3 m

There is a second exemption that catches people out, in Part 3 of Schedule 1 (clause 41). A retaining wall up to 3 m can be exempt where the design is carried out or reviewed by a chartered professional engineer, the wall is in a rural zone under the district plan (not a rural-residential zone), and it is set back from every legal boundary and existing building by at least the height of the wall. All three conditions apply together. A typical urban or lifestyle-block section will not qualify, and a wall carrying a surcharge is outside the exemption altogether. In practice it means you should treat anything over 1.5 m as a consented wall unless you have the engineer, the zone and the setback confirmed in writing. When a client wants to know whether the council will mind, point them at the council’s building team before you price the job, because a wrong guess means stopping work halfway through.

Engineer design, PS1 and PS4

Once a wall needs a building consent, it needs a design that demonstrates compliance with Building Code clause B1 Structure, which for a wall over 1.5 m or under surcharge almost always means a Chartered Professional Engineer. The engineer supplies a PS1 Producer Statement — Design with the plans that go to the council. If the engineer is also reviewing construction, they provide a PS4 Producer Statement — Construction Review at the end, which supports the code compliance certificate. As the contractor, your job is to build what was consented, keep the engineer’s design and statements on the job file, and tell the engineer in time for their inspections. Councils often make inspections of footings, drainage and backfill conditions of the consent, so a wall backfilled before inspection can mean excavating it again. Our nz-building-code section on retaining walls covers the build-off-the-shelf limits in more detail, and Toolie’s producer statement register keeps the PS1 and PS4 against the job.

• Retains 1.5 m or less and no surcharge: exempt (cl 20), still must meet the Code
• Over 1.5 m, or any surcharge: building consent and engineered design
• Up to 3 m in a rural zone: only with CPEng design, and a setback at least equal to wall height (cl 41)
• Consented wall: PS1 with the application, PS4 if the engineer reviews construction

Before you dig: services and trench safety

Retaining walls mean digging, and landscapers hit services all the time. As a PCBU under the Health and Safety at Work Act 2015 you have to manage the risk of striking underground services, and the practical step is a beforeUdig enquiry. beforeUdig is a free online service that gives anyone excavating information about cable, pipe and asset locations from utility owners, and it should be done before every dig, with services then located and marked on site. Deeper excavations bring a second obligation. WorkSafe treats work in a pit, trench or excavation where a person works in a space more than 1.5 m deep and deeper than its width at the top as particular hazardous work, which needs at least 24 hours’ notice to WorkSafe. So does work in an excavation with a vertical face over 5 m high and steeper than 1 horizontal to 2 vertical. Most garden walls never come close, but a cut for a driveway or a basement-level terrace can, and shoring, benching or battering is the way you keep people safe in anything deep. Earthworks can also need resource consent under district or regional plan rules, particularly near water.

Quoting and sequencing the paperwork

The cleanest way to avoid a dispute is to put the paperwork in the quote. State the wall height as retained depth, state whether anything sits above it, and say plainly whether a consent and engineer are included or the client’s responsibility, and what that costs and how long it takes. Council processing and the engineer’s design add weeks, and the client should know that before they plan a pool party. Itemise the engineer and consent separately from materials and labour so the client can see what the rules cost. Allow for drainage, geotextile, backfill aggregate and disposal of spoil, which are the lines that get left off garden-wall quotes. Do not start digging until the consent is granted, if one is required, and do not close up until the inspections have been passed. Variations are common once the engineer sees the site, so get any change in height or footing size agreed in writing before the work goes ahead.

Where Toolie fits in

Toolie’s landscaping pack runs this check for you at quote stage. Enter the retained height, whether there is a surcharge, whether the wall supports a structure, and for walls over 1.5 m whether the site is a rural zone, the distance to the nearest boundary or building, and whether an engineer is designing it. It then says whether the clause 20 or clause 41 exemption applies or a consent and engineered design is needed, with the reasoning shown. When consent is required it adds the building consent, engineer design and PS1/PS4 records to the job, and the job cannot be marked complete until they are done. The same check flags pool barriers, shared boundary fences, earthworks and digging jobs, so the beforeUdig and trench items are on the list rather than in your head. Treat it as a prompt and a record. The council and your engineer decide what is required for a given site.

Sources

Official sources this guide relies on. Rules change, so check the current version before relying on a date or threshold.

• Building Act 2004, Schedule 1 (clauses 20 and 41), legislation.govt.nz
• WorkSafe NZ: Particular hazardous work (notifiable works)
• beforeUdig: free online service for locating underground assets
• MBIE Building Performance: building work that doesn't need a consent

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