Deep earthworks in New Zealand sit at the intersection of building consent law, health and safety regulations, and practical site safety. The short answer is: it depends on the depth, scope, and site conditions — but there are clear legal limits that both homeowners and landscapers need to understand before a single spade goes in the ground.
What Counts as Deep Earthworks?
Earthworks refers to any excavation, cutting, filling, or reshaping of land. In a landscaping context this might include retaining walls, drainage trenches, pond excavation, or significant land levelling. The term deep earthworks generally refers to excavations beyond 1.5 metres in depth, though even shallower work can trigger consent or safety requirements depending on the situation.
In New Zealand, earthworks are regulated under:
- The NZ Building Code (administered by MBIE Building Performance)
- The Resource Management Act (RMA) — your local district or city council will have earthworks rules in their district plan
- WorkSafe NZ health and safety legislation
Do You Need a Building Consent for Earthworks?
Not all earthworks require a building consent, but many do. Under Schedule 1 of the Building Act, some minor earthworks are exempt — however, the exemptions have conditions and vary by council. Always check with your local council before starting, as rules differ significantly between regions.
Generally, you are more likely to need consent when:
- Excavations are deeper than 1.5 metres
- The work is near a boundary, existing structure, or retaining wall
- A retaining wall over 1.5 metres high is involved
- The site is on unstable, sloping, or flood-prone land
- The work could affect neighbouring properties or public infrastructure
For guidance on what triggers consent, visit MBIE Building Performance or speak directly with your local council's building department.
Health & Safety: The Legal Obligations
This is where things get very serious. Under the Health and Safety at Work Act 2015, any excavation deeper than 1.5 metres requires specific controls to manage the risk of collapse and requires specific controls. WorkSafe NZ sets out clear requirements including:
- Shoring or battering the sides of the excavation to prevent collapse
- Keeping people out of unsupported trenches deeper than 1.5 metres
- Having a safe system of work documented before starting
- Ensuring workers are competent and trained for the task
A landscaper working without appropriate shoring equipment, safety plans, or trained personnel on deep excavations is not just cutting corners — they are breaking the law and putting lives at risk. Trench collapses can be fatal and happen without warning.
What Equipment Is Actually Required?
For excavations beyond about 600 mm–1 metre, hand tools alone become impractical and potentially unsafe. Deeper work typically requires:
- Mechanical excavators (diggers/excavators) — mini excavators are common on residential sites
- Shoring systems — hydraulic or timber shoring to support trench walls
- Dewatering pumps if groundwater is present
- Spoil management — safe placement of excavated material away from the trench edge
A landscaper who does not have access to this equipment, or who is not trained to use it safely, should not be attempting deep earthworks. This is not a reflection on their landscaping skill — it is simply a different discipline requiring specialist knowledge and gear.
What Can a Landscaper Legally Do?
A qualified landscaper can legally carry out a wide range of earthworks, including:
- Shallow excavations (typically under 600 mm) for garden beds, paths, and drainage
- Topsoil stripping and site preparation
- Minor land contouring and levelling
- Installing retaining walls up to 1.5 metres (consent thresholds vary — check with your council)
- Operating machinery they are trained and competent to use
For deeper or more complex work, a good landscaper will either have the right equipment and training themselves, or will subcontract to a civil contractor or earthworks specialist. This is standard practice on larger residential projects.
Proximity to Services: An Extra Caution
Before any excavation, underground services must be located. This includes water mains, gas lines, electrical cables, and telecommunications. In NZ, you can contact Dial Before You Dig (now called beforeUdig) to get service plans for your site. Striking a buried service can be deadly and is the responsibility of the person doing the work.
For work near gas or electrical infrastructure, WorkSafe NZ has specific safe-distance requirements.
When to Call a Professional
You should engage a specialist civil contractor or earthworks company — rather than a general landscaper alone — when:
- Any excavation will exceed 1.5 metres in depth
- The site is on a slope, near a boundary, or has unstable soils
- A building consent has been required by your council
- Underground services are nearby
- The project involves significant cut-and-fill or retaining structures
A reputable landscaper will tell you honestly when a job is outside their scope. If a landscaper quotes to do deep earthworks with hand tools only and no safety plan, treat that as a red flag.
You can find qualified local landscapers and earthworks contractors on tradedirectory.co.nz who can assess your site and advise on the right approach.
Licensed Building Practitioner (LBP)
