Concrete slab consent in NZ: driveways, house slabs and the paperwork behind each pour

Driveways, paths and slabs: the usual consent position

Under the Building Act 2004, work that forms part of a building’s structure needs a building consent unless Schedule 1 exempts it. Plain residential driveways, paths and non-structural slabs on the ground are generally treated as exempt, and so are retaining walls that retain 1.5 m or less and carry no surcharge (Schedule 1, clause 20). A concrete retaining wall taller than that, or one holding up a driveway or a building, needs a consent and an engineer’s design. A slab that forms the floor or foundation of a building is different: it is part of the structure, and its design, inspections and sign-off sit within the consent for the building. Two cautions apply to every exempt pour. Exempt work must still comply with the Building Code, so cover, falls and durability matter even without a consent. And the council’s district plan can limit hard surfacing, stormwater runoff and driveway crossings separately, so a driveway can need a vehicle crossing approval even when the slab itself does not need a consent. If you are asked to confirm “no consent needed”, say it is generally exempt and the council can confirm in a borderline case.

When a pour is restricted building work

Restricted building work is the part of residential building work that must be carried out or supervised by a Licensed Building Practitioner. It applies to the structure and weathertightness of houses and small to medium apartment buildings, and foundations are part of the structure. For concrete, the relevant licence class is Foundations, which the LBP scheme divides into two areas of practice: concrete foundation walls and concrete slab-on-ground, and concrete or timber pile foundations. If you are pouring the slab or footings for a new house or an extension, the work must be done or supervised by an LBP whose licence covers it, and they have to give the owner and the council a Record of Building Work when they finish. The design side is separate, since a Design LBP covers the plans rather than the pour. Check the LBP’s licence class and status on the public register before you start, and be clear on the contract about who is the supervising LBP, as it is the person who signs the record and carries the responsibility.

Which standards you will be working to

Two concrete standards come up repeatedly. NZS 3101 is the Concrete Structures Standard, which engineers use for design, and the strength grade, cover to reinforcement and exposure class on a set of consented plans come from the engineer’s application of it. NZS 3109 covers concrete construction: specifying, placing and curing. For ordinary house slabs and footings, the Building Code acceptable solutions and the NZS 3604 timber-framed buildings standard set many of the details, including minimum concrete strength, edge thickening and reinforcing, and they lean on NZS 3109 for how concrete is made and placed. You do not need the full text of each on the truck, but you do need to know which one the consented drawings call up, and what the mix, cover and curing requirements say. If the plans and the standard disagree, the plans win and the question goes to the designer before you pour, not after.

Inspections, pumps and what happens on the day

A consented slab or footing is normally inspected by the council before the pour, with reinforcing, cover, laps, formwork and the excavation checked, and sometimes by the engineer as well. Order the concrete only once the inspection has passed, as a booked truck on a failed inspection is a very expensive argument. On the day, record the delivery docket details, volume ordered against delivered, slump, any admixtures and the weather. Concrete pumps bring their own hazards. Keep people out from under the boom and the delivery hose, follow the pump operator’s instructions, and check overhead lines and ground conditions for outriggers before the pump is set up. WorkSafe’s notifiable work list includes lifting plant above certain loads and heights but excludes self-propelled mobile cranes, so confirm with the pump or crane operator whether notification applies rather than guessing. Concrete in freezing air can be damaged by ice in the fresh mix, so protect it and write down what you did.

Pour records worth keeping

Nobody gets sued over a pour record, but nearly every dispute is helped by one. For each pour, keep the supplier and docket numbers, the specified strength in MPa, volume ordered and delivered, the mix and slump, weather and air temperature, who inspected beforehand and when, whether the reinforcement was checked, the curing method and how long it ran, and any test cylinder results with the lab reference. A 7-day and 28-day result lined up against the specified strength gives the engineer something to assess if there is ever a question. For structural concrete, this is the evidence your LBP draws on for the Record of Building Work and that the council may ask for before it issues the code compliance certificate. Even on an exempt driveway, a short record of strength, volume, date and curing protects you if a customer complains about cracking months later. Photographs of the reinforcing and the finished surface take seconds and have settled many arguments.

• Supplier, docket numbers, specified MPa, slump and admixtures
• Volume ordered against volume delivered
• Weather and air temperature at the pour
• Pre-pour inspection by council or engineer, and the date passed
• Reinforcement check: cover, laps, chairs
• Curing method and duration, and cylinder results with the lab reference

How Toolie handles the paperwork

Toolie’s concreter pack asks a few questions about the job and tells you which requirements apply and why. Mark it as structural concrete for a building and it flags building consent and LBP supervision from the Foundations class as required, and the job cannot be marked complete until they are addressed. Mark a retaining wall over 1.5 m and it flags consent; a plain driveway shows as generally exempt, with a reminder to check with the council. The pour records register holds the fields above, shows the date curing ends, reports the over or under delivery as a volume and percentage, warns if the pre-pour inspection or reinforcement check is not ticked, notes air temperatures at or below freezing, and shows 7 and 28-day cylinder results next to the specified strength. It records the result without giving a pass or fail verdict. The engineer and supplier assess compliance. Toolie does not hold your LBP licence or issue the Record of Building Work.

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 and restricted building work), legislation.govt.nz
• Licensed Building Practitioners: licensing classes (Foundations)
• WorkSafe NZ: Particular hazardous work (notifiable works)
• MBIE Building Performance: building work that doesn't need a consent

Related: concrete calculator · footing sizes · retaining walls · producer statements · consent tracker. Back to concreters software · software for every trade.