Yes, a retaining wall builder in New Zealand can legally subcontract parts of a project to other tradespeople. This is common practice on larger or more complex jobs where specialist skills — such as drainage, concrete work, or structural engineering — are needed. However, subcontracting doesn't remove anyone's legal obligations: every tradesperson on site must hold the correct qualifications for their work, and the overall project must still comply with the NZ Building Code.
How Subcontracting Works on a Retaining Wall Project
When you hire a retaining wall builder as your principal contractor, they take overall responsibility for delivering the project. They may then bring in subcontractors to handle specific tasks. Common examples include:
- Drainage installers – retaining walls almost always require proper drainage behind them to relieve hydrostatic pressure
- Concrete pourers or blocklayers – for mass concrete or concrete block walls
- Structural engineers – to design walls over 1.5 m high or in challenging ground conditions
- Electricians – if lighting or irrigation controls are involved
- Plumbers or drainlayers – for any stormwater or subsoil drainage connections
Your contract is typically with the principal contractor, who manages and is accountable for the subcontractors' work. Always confirm this in writing before work begins.
What the NZ Building Code and Consents Require
Retaining walls over 1.5 metres high (or those retaining a surcharge such as a driveway or building) generally require a building consent from your local council. Some lower walls may be exempt under Schedule 1 of the Building Act — but always confirm with your council before assuming an exemption applies, as site conditions, soil type, and proximity to boundaries all matter.
Where a consent is required, the work must be carried out in accordance with the approved plans and inspected at key stages. Subcontractors must perform their portions of the work to the same standard. The Licensed Building Practitioners (LBP) scheme is relevant here: certain restricted building work — including structural elements — must be carried out or supervised by an LBP-licensed tradesperson. Your principal contractor should be able to confirm their LBP licence and the licence class that covers the work.
BRANZ provides technical guidance on retaining wall construction that both builders and homeowners can reference.
Restricted Trades Within a Retaining Wall Project
Some subcontracted work is legally restricted to licensed professionals regardless of who the principal contractor is:
Electrical Work
Any electrical installation — including outdoor lighting, pumps, or irrigation timers — is restricted electrical work and must be carried out by a registered electrician. Check registration via the Electrical Workers Registration Board (EWRB).
Plumbing and Drainlaying
Connecting subsoil drainage or stormwater pipes to the public system is restricted work under the Plumbers, Gasfitters and Drainlayers Act. Only a licensed drainlayer can legally do this. Verify credentials through the Plumbers, Gasfitters and Drainlayers Board (PGDB).
Safety note: Never allow unlicensed people to carry out restricted electrical, plumbing, or drainlaying work. Doing so is illegal, may void your insurance, and can create serious safety hazards.
Your Rights as a Homeowner
As the client, you have the right to:
- Ask who will be on site and what qualifications each subcontractor holds
- Request copies of licences for any restricted trade work
- See the building consent and understand what inspections are required
- Receive a Record of Work from licensed tradespeople once restricted work is complete
A reputable builder will be transparent about their subcontractors. If a builder is evasive about who is doing the work or whether they are qualified, treat that as a red flag.
What to Check Before Signing a Contract
| Item to Check | Why It Matters |
|---|---|
| Principal contractor's LBP licence | Confirms they can legally carry out or supervise restricted building work |
| Subcontractor licences (electrical, drainlaying) | Legally required for restricted trades |
| Public liability insurance | Protects you if something goes wrong |
| Building consent (if required) | Ensures the wall is legal and inspected |
| Written contract covering subcontractors | Clarifies accountability and payment terms |
When to Call a Professional
For any retaining wall over 1 m high, on a sloped section, near a boundary, or where ground conditions are uncertain, engaging a qualified retaining wall builder is strongly recommended. Complex sites may also need a geotechnical engineer to assess soil stability before design begins. The MBIE Building Performance website has useful guidance on when professional input is required.
You can find qualified, local retaining wall builders and related tradespeople on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
