The more information you give an excavation contractor upfront, the more accurate — and comparable — your quotes will be. Vague requests lead to vague pricing, and that can mean nasty surprises once the digger is on site. Here's a straightforward guide to what NZ excavation contractors need to know before they can give you a solid number.
Your Site Location and Access
Start with the basics: your full property address and, if possible, a site plan or survey map. Contractors need to assess how easy it is to get machinery onto your property. Key access details include:
- Gate and driveway width — can a full-size excavator and truck get through?
- Overhead clearance — power lines, trees, or structures that could restrict machine height
- Ground conditions on the access route — soft or wet ground can damage lawns and driveways
- Proximity to neighbouring properties — tight urban sections require smaller, slower machines
If your site is in a rural area or on a steep slope, mention that too. Hill country work in regions like Northland, Waikato, or the West Coast often requires specialised equipment and extra time.
The Scope of Work
Be as specific as you can about what you need excavated and why. Common residential excavation jobs include:
- Foundation excavation for a new build or extension
- Trenching for drainage, water supply, or electrical conduit
- Swimming pool or spa excavation
- Retaining wall footings
- Driveway or yard cut and fill
- Septic tank or soakage field installation
For each job, try to provide approximate dimensions — length, width, and depth. Even rough measurements help a contractor estimate machine hours and spoil removal volumes.
Soil and Ground Conditions
Soil type has a huge impact on excavation cost and method. Hard clay, rock, or contaminated fill all take longer and cost more to dig than loose topsoil. If you've had a geotechnical report done (often required for building consents under the NZ Building Code), share it with your contractor. Otherwise, describe what you know:
- Is the ground generally soft, firm, or rocky?
- Has the site been filled previously?
- Does it get waterlogged in wet weather?
- Are there any known underground hazards?
If you're unsure, a reputable contractor will often do a site visit before quoting — and that's worth arranging.
Underground Services
This is critical for safety. Before any excavation begins, you need to know where underground services run across your property. These include:
- Water supply pipes
- Stormwater and wastewater drains
- Gas lines
- Electrical cables
- Telecommunications cables
Use the free beforeUdig service (beforeudig.co.nz) to get a plans request from utility companies. Share any service plans you receive with your contractor. Striking a live cable or gas line is extremely dangerous and can result in serious injury, costly repairs, and legal liability.
WorkSafe NZ has clear guidance on safe excavation practices — your contractor should be following these as a matter of course.
Spoil Removal and Disposal
Excavation produces a lot of material. Clarify with your contractor:
- Do you want the spoil removed from site, or can it be stockpiled or spread elsewhere on your property?
- Is there any contaminated material (old fill, asbestos-containing soil, chemical spills) that may require specialist disposal?
- Are there trees, roots, or concrete to be broken up and removed?
Spoil removal is often charged separately, so being clear about this upfront avoids bill shock later.
Consents and Compliance
Some excavation work requires a building consent — particularly if it involves earthworks over a certain volume or affects land stability. Requirements vary by council, so always check with your local council before work begins. MBIE Building Performance has useful guidance on Schedule 1 exemptions, but confirm with your council whether your specific project qualifies.
If your project involves drainage or plumbing connections, note that connecting to the public wastewater or stormwater network is restricted work that must be carried out by a licensed drainlayer registered with the Plumbers, Gasfitters and Drainlayers Board. Make sure your excavation contractor and your drainlayer are coordinating.
Timing and Site Conditions
Let your contractor know:
- Your preferred start date and any deadline pressures
- Whether the site will be occupied during work (people, pets, vehicles to manage)
- Any wet weather concerns — NZ winters can make some sites inaccessible for weeks
- Whether you need traffic management if work is near a road
A Quick Reference Checklist
| Information | Why It Matters |
|---|---|
| Full address and site plan | Helps assess access and layout |
| Scope and dimensions of work | Determines machine size and hours |
| Soil type / geotech report | Affects dig rate and method |
| Underground service plans | Essential for safety |
| Spoil removal preference | Affects truck and disposal costs |
| Consent status | Avoids compliance issues |
| Timing and access constraints | Affects scheduling and pricing |
When to Call a Professional
Always use a qualified, experienced excavation contractor for anything beyond very minor hand-digging. For work near underground services, on steep or unstable ground, or involving significant earthworks, a professional is essential. BRANZ provides research and guidance on best practice for NZ construction sites. If your project involves drainage connections, you'll also need a licensed drainlayer — find both excavation contractors and drainlayers on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
