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Hidden Cost Checklist
June 2026
Many homeowners underestimate the additional costs beyond the house itself.
Use this checklist to ensure you have allowed for all potential expenses.
Site & Ground Works
☐ Earthworks and site preparation
☐ Excavation or retaining walls
☐ Drainage and stormwater
☐ Soil testing and geotechnical reports
☐ Erosion and sediment control
☐ Piling (for poor ground conditions)
Design & Professional Fees
☐ Architectural design
☐ Structural engineering
☐ Building & resource consent fees
☐ Surveying fees
☐ Contract works insurance
☐ Specialist reports (acoustic, traffic, flood, etc. if required)
Services & Utilities
☐ Water connection
☐ Wastewater/stormwater connection
☐ Power connection
☐ Fibre internet installation
☐ Council development contributions
☐ Temporary power during construction
Structural / Spec Upgrades
☐ Window glazing upgrades
☐ Insulation upgrades
☐ Bracing / engineering upgrades
☐ Foundation upgrades (e.g. slab → rib raft)
External Works
☐ Driveway
☐ Fencing
☐ Decking
☐ Landscaping
☐ Outdoor lighting
☐ Retaining walls
Interior Upgrades
☐ Appliance upgrades
☐ Flooring upgrades
☐ Bathroom fixtures
☐ Wardrobe fit-outs
☐ Window coverings
Nice-to-Have Costs That Become Must-Haves
☐ Heat pumps / HVAC systems
☐ Alarm systems / security
☐ Garage carpet or storage fit-out
☐ Letterbox, clothesline, bins area
Compliance & Handover Costs
☐ Code Compliance Certificate (CCC) fees
☐ Final inspections and certifications
☐ As-built plans / documentation
☐ Professional cleaning before move-in
Finance & Holding Costs
☐ Interest during construction
☐ Rent while building (if applicable)
☐ Loan setup / legal costs
☐ Valuation fees
Risk Factors
☐ Weather delays
☐ Material price increases (if not fixed price)
☐ Labour availability
☐ Design changes during build
Price Cost allowances
Builders often allow Prime Cost (PC) allowances for items that have not yet been selected. These allowances are often based on basic or standard specifications and may not reflect the true cost of higher-quality or upgraded finishes, which can lead to budget overruns.
Ask the builder whether these allowances reflect realistic market prices.
Also check the level of Provisional Sums (PS) in your quote, as these are estimates only and can increase during construction.
Recommended Budget Buffer
Most budget blowouts don’t come from the house itself — they come from everything around it. Many builders recommend allowing a 10–15% contingency for unexpected costs during construction. This protects your project if prices change or unforeseen site issues arise.
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