Why guarantees matter when hiring an excavator
Hiring an excavator is often the first step in a larger project — a new driveway, retaining wall, drainage upgrade, site cut, trenching for services, or prep for a garage or extension. It is also one of the most common points where hidden problems are created. Poor excavation can lead to drainage failures, slumping, damaged pipes, unsafe batter slopes, and extra costs for later trades.
That is why it is worth asking not just what the excavator will do, but what they will stand behind after the job is finished. In New Zealand, the main protections come from:
- a written workmanship guarantee from the contractor - product or manufacturer warranties on materials and components they supply - your rights under the Consumer Guarantees Act 1993 (CGA) - contract law and, in some cases, the Disputes Tribunal or District Court if things go wrong
A good excavator should be willing to explain these clearly before work starts.
Workmanship guarantees: what a good excavator should offer
A workmanship guarantee is the contractor’s promise that their own labour will be completed with reasonable care and skill and, if something they did fails because of poor workmanship, they will put it right.
For excavation work, a workmanship guarantee should ideally state:
- what work is covered, such as excavation, trenching, backfilling, compaction, levelling, spoil removal and site reinstatement - how long the guarantee lasts - what counts as a defect or failure - whether the excavator will repair, redo or pay for the defect to be fixed by someone else - any exclusions, such as movement caused by ground conditions, flooding, tree roots, or work altered by others after completion - how to make a claim and how quickly they will respond
A time period of 6 to 12 months is common for workmanship guarantees in trades, but the real value is in the wording, not just the length. Some excavation issues do not show up immediately, especially after wet weather or seasonal ground movement, so it is sensible to ask whether the guarantee covers problems discovered after the first rain or through a change of season.
Be cautious if a contractor says they offer a “lifetime guarantee” without any written terms. Always ask for the actual document.
What a workmanship guarantee should and should not cover
Excavation is different from many other trades because the outcome can depend heavily on soil type, groundwater, hidden services, and weather. A fair guarantee should recognise that.
A reasonable guarantee usually covers
- poor compaction that causes obvious settlement in areas they backfilled - incorrectly excavated levels that do not match the agreed scope - failure to restore drainage falls as specified in the quote or plan - damage caused by the excavator’s machine or operator to neighbouring structures, lawns, fences or services - leaving the site in a hazardous or unfinished condition contrary to the contract
A guarantee usually does not cover
- natural ground movement, subsidence or erosion outside the contractor’s control - hidden underground conditions that could not reasonably have been known beforehand - defects caused by another trade, owner, or later alterations to the site - work carried out strictly to the homeowner’s instructions where those instructions were unsafe or against advice - issues caused by flood events, earthquakes or other external events
If the job involves retaining walls, foundations, drainage or driveway construction, clarify exactly where the excavator’s responsibility ends and the next trade’s begins. Many disputes happen because one contractor assumes another will finish the grade, compact the base, or connect the drains.
Product warranties: what they are and why they matter
Excavators often supply or install products as part of the job, even if the main service is labour. Product warranties are different from workmanship guarantees.
They may apply to:
- drainage pipe, fittings and geotextile fabric - retaining wall blocks, timber, steel or concrete elements supplied by the contractor - geogrid, membrane, or erosion control products - stabilisation materials or surfacing products if included in the scope - concrete or premixed products delivered to site
A product warranty is usually provided by the manufacturer or supplier, not the excavator, although the excavator should pass on the warranty details and any required documentation.
Ask these questions about product warranties
- Who is the actual warrantor — the supplier, manufacturer or excavator? - How long does the warranty last? - What is covered: replacement only, labour, transport, or consequential damage? - Does the warranty require installation by a qualified person or in a particular way? - What paperwork must you keep, such as invoices, batch numbers or installation records?
Important: if the excavator supplies the product and installs it incorrectly, you may have both a product warranty issue and a workmanship issue. The contractor should not try to push all responsibility onto the manufacturer if the problem was their installation.
The Consumer Guarantees Act and excavation work in NZ
The Consumer Guarantees Act 1993 gives homeowners powerful rights when they hire a business for services in New Zealand, including excavation services.
Under the CGA, services must be:
- carried out with reasonable care and skill - fit for a particular purpose if the homeowner told the contractor about that purpose and relied on their judgement - completed within a reasonable time if no time frame was agreed - charged at a reasonable price if no price was agreed in advance
These rights apply whether or not the contractor offers a separate guarantee. In other words, a contractor cannot simply say “no warranty” and avoid CGA obligations if they are dealing with a consumer.
For excavation, this is especially relevant where the homeowner has clearly explained the purpose of the job, for example:
- preparing ground for a consented garage slab - excavating a trench for a stormwater line - levelling a section for a retaining wall or sleepout - digging near existing utilities and boundary structures
If the excavator says the work is suitable for the intended purpose, and it later turns out to be faulty because they did not exercise reasonable care and skill, the CGA may give you remedies.
Common mistakes to avoid when checking guarantees
Many homeowners focus on price and machine size, but the contract terms matter just as much. Watch for these common mistakes:
- not getting the scope in writing - assuming “all work guaranteed” means everything, including hidden ground conditions - relying on a verbal promise only - not checking whether subcontractors are covered under the same guarantee - not confirming who is responsible for reinstatement of lawns, paving, fences or gardens - not asking for warranty documents for any supplied materials - not verifying whether the contractor has the right qualifications for any restricted work they are touching
If the job includes plumbing, gasfitting or drainlaying, those are restricted trades under the Plumbers, Gasfitters and Drainlayers Board (PGDB) framework and must be done by, or under the supervision of, appropriately authorised people. Electrical work is regulated by the Electrical Workers Registration Board (EWRB). An excavator can dig around these services, but should not carry out work that lawfully belongs to another regulated trade unless they are properly authorised.
Also remember that some excavation-related building work may require a building consent from your local council, especially where it affects foundations, retaining walls over certain heights, drainage systems or structural elements. A good contractor should tell you when consent or inspection issues may be involved, but the homeowner should always confirm with the council or designer.
What to ask for before you accept a quote
Before you sign, ask for multiple written quotes and compare them carefully. Cheapest is not always best if it leaves you with no protection when something goes wrong.
Ask each excavator to provide:
- a written scope of work - the machinery and labour included - who is responsible for set-out, locating services, and spoil removal - any exclusions, assumptions or site access limits - the workmanship guarantee terms - product warranty details for any materials supplied - evidence of insurance, including public liability cover - their company details and, where relevant, licence or registration details for related work
It also helps to ask how they handle uncertain ground conditions, particularly in older parts of NZ towns and cities where fill, clay, high groundwater or undocumented services can create surprises.
A simple comparison table for homeowners
| Protection type | What it covers | Who provides it | What to check | |---|---|---|---| | Workmanship guarantee | The excavator’s labour and installation quality | The contractor | Duration, exclusions, claim process, whether repairs are at their cost | | Product warranty | Defects in supplied materials or components | Manufacturer or supplier | Length, proof of purchase, installation requirements, exclusions | | Consumer Guarantees Act | Services done with reasonable care and skill; fit for purpose; reasonable time/price | Law | Whether the contractor understood the intended use and scope | | Insurance | Sudden accidental damage and some liability risks | Contractor’s insurer | Public liability amount, what is excluded, whether it is current |
What to do if the excavation work is faulty
If something is wrong, act quickly and document everything.
Step 1: Keep records
- take dated photos and videos - keep the quote, contract, texts, emails and invoices - note when you first noticed the problem - record any damage or safety concerns - if possible, get an independent opinion from another contractor or engineer
Step 2: Notify the excavator in writing
Explain the problem clearly and give them a reasonable chance to inspect and respond. State what outcome you want — for example, repair, re-excavation, proper compaction, or reimbursement for rectification work.
Step 3: Refer to the contract and the CGA
If the contractor resists, point out the workmanship guarantee and your rights under the Consumer Guarantees Act. Keep the tone factual and professional.
Step 4: Escalate if needed
If the problem is not resolved, you may consider:
- the Disputes Tribunal for lower-value claims within its limit - a formal demand for rectification or compensation - mediation or a lawyer’s letter for more serious matters - the District Court for larger or more complex disputes
If the excavation affected regulated work, such as drainage or electrical services, you may also need to contact the relevant board or the utility owner if safety is involved.
What a trustworthy excavator should do after a problem is found
A reliable excavator will not disappear once the invoice is paid. Good practice includes:
- responding promptly to fault reports - attending site to inspect the issue - explaining whether the issue is workmanship, product failure, weather-related, or caused by a third party - arranging repairs or a practical remedy where they are responsible - keeping the homeowner updated if more than one trade is involved
If a contractor refuses to inspect, delays unreasonably, or blames everyone else without evidence, that is a warning sign.
Final checks before you hire
A strong guarantee is only one part of choosing the right excavator, but it is an important one. Before you decide, make sure you:
- get at least two or three written quotes - compare scope, not just price - check insurance and references - confirm who is responsible for any related restricted or consented work - insist on written workmanship guarantee terms - keep all paperwork in one place
Clear terms at the start can save a lot of stress later, especially on jobs where drainage, ground conditions and other trades all depend on the excavation being done properly.