Disagreeing with a quantity surveyor's (QS) cost assessment can feel stressful, especially when you're mid-project and big decisions hinge on the numbers. The good news is that you have clear options — from simply asking for clarification right through to formal dispute resolution — and working through them methodically usually leads to a fair outcome.
Start by Asking for a Detailed Breakdown
Before assuming the assessment is wrong, ask your QS to walk you through their figures. A professional quantity surveyor should be able to provide a detailed cost plan or bill of quantities that shows exactly how each line item was calculated. Common areas where homeowners question figures include:
- Preliminaries and overheads — site establishment, project management fees, and contractor margins
- Contingency allowances — typically 10–15% for residential projects, though this varies
- Material specifications — whether the QS has priced to the correct grade or brand of product
- Labour rates — which can vary significantly by region and trade
Sometimes a discrepancy is simply a misunderstanding about scope or specification. Clarifying these points in writing is always a good first step.
Check the Scope of Work and Assumptions
Every cost assessment is based on a set of assumptions and exclusions. Ask your QS to confirm:
- What drawings, specifications, or information they based the assessment on
- What is explicitly excluded (e.g., council fees, geotechnical investigations, landscaping)
- Whether GST is included or excluded
- What stage of design the estimate reflects (concept, developed design, or construction documentation)
Early-stage estimates carry a wider margin of error than those based on full construction documents. BRANZ research consistently shows that cost certainty improves significantly as design detail increases — so if your QS assessed costs at concept stage, a higher variance is expected and normal.
Get a Second Opinion
If you've reviewed the breakdown and still believe the figures are materially off, you are entirely within your rights to commission a second independent QS assessment. This is standard practice in the construction industry and a reputable QS will not take offence at a reasonable request for a peer review.
When comparing two assessments, look at:
| Factor | What to Compare |
|---|---|
| Scope covered | Are both QSs pricing the same work? |
| Specification level | Same materials and finishes assumed? |
| Contingency % | Is one more conservative than the other? |
| Market timing | Were both assessments done at the same time? |
Construction costs in New Zealand have been volatile in recent years, so even a few months between assessments can produce different results. MBIE Building Performance publishes guidance on the building consent process that can help you understand what cost information councils may require.
Raise a Formal Complaint With the QS
If you believe your QS has made a genuine error — not just a difference of professional opinion — raise it formally in writing. Most QS firms have an internal complaints process. Your engagement letter or contract should outline this. Keep records of all correspondence.
Key points to include in a written complaint:
- Specific line items you dispute and why
- Any supporting evidence (e.g., supplier quotes, comparable project costs)
- The outcome you are seeking (revised assessment, fee reduction, etc.)
Professional Body Complaints
Quantity surveyors in New Zealand are not subject to a statutory licensing regime in the same way that electricians or plumbers are. However, many practising QSs are members of the New Zealand Institute of Quantity Surveyors (NZIQS) or hold RICS (Royal Institution of Chartered Surveyors) membership. Both bodies have professional conduct standards and formal complaints processes.
If your QS is a member of either body, you can escalate an unresolved complaint to them. Check your QS's credentials and membership status before engaging them — this gives you an important avenue for recourse if things go wrong.
Dispute Resolution and Legal Options
For significant financial disputes, New Zealand's Construction Contracts Act 2002 provides a framework for adjudication — a relatively fast and cost-effective form of dispute resolution compared to litigation. This is more commonly used in commercial contexts, but it can apply to residential contracts depending on how your engagement is structured.
Consumer NZ offers guidance on resolving disputes with tradespeople and service providers more broadly. For smaller disputes, the Disputes Tribunal is another accessible option.
Always seek independent legal advice before escalating to formal proceedings.
When to Call a Professional
If the cost discrepancy is significant — say, more than 10–15% of your total project budget — or if it's affecting a building consent application, insurance claim, or property transaction, it's worth engaging a second qualified QS promptly. A QS can also help you interpret NZ Building Code compliance costs and ensure your project budget reflects realistic current market rates.
You can find qualified quantity surveyors in your area through tradedirectory.co.nz.
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