When clients think about cost overruns in construction, they often assume the cause is poor estimating or rising material prices. In reality, changes made during construction are one of the biggest and most avoidable drivers of increased costs on residential projects.
For architecturally designed homes in particular, changes after construction has started can have a significant impact on budget, programme, and overall quality. Understanding why this happens and how to reduce the risk can save homeowners time, money, and stress.
A variation is any change to the agreed scope of work afterthe building contract has been signed. Variations commonly include:
• Changes to layouts, dimensions, or structure
• Changes to materials and finishes
• Adding new elements such as joinery, skylights, or services
• Design changes required by compliance, engineering, or site conditions
Some variations are unavoidable, but many are the result of decisions being made too late in the process.
Clients are often surprised by how expensive a seemingly small change can be. Construction is a tightly sequenced process, and even minor alterations can affect multiple trades.
Common reasons costs increase include:
Rework and aborted work
If framing, services, or linings are already installed, changes may require completed work to be removed and rebuilt.
Programme delays
Changes often pause work while new details are resolved, materials are re-ordered, or consent amendments are processed. Delays increase site and subcontractor costs.
Higher material pricing
Late changes usually involve small orders at higher rates rather than bulk pricing secured earlier in the project.
Consent and compliance impacts
In New Zealand, design changes can require amended building consents, additional inspections, and updated documentation, adding time and professional fees.
From experience, most construction changes fall into a few predictable categories:
Incomplete documentation
When drawings lack sufficient detail, decisions are pushed into the build phase where changes are more expensive.
Poor budget alignment
If a design is not properly cost checked before consent, value driven changes often occur during construction.
Late selections
Joinery, lighting, tapware, cladding, and flooring should be finalised early.Delayed selections frequently lead to variations.
Changing priorities
As clients see the build progress, ideas naturally evolve. Without a clear decision framework, this can result in scope creep.
While no project is completely free of changes, several strategies significantly reduce variation risk:
Invest in detailed design upfront
Well resolved documentation allows for accurate pricing and smoother construction.
Engage a builder early
Early builder involvement helps identify cost, buildability, and sequencing issues before construction begins.
Finalise key selections early
Locking in finishes and fixtures improves pricing certainty and reduces rushed decisions.
Understand the real cost of change
A transparent variation process helps clients weigh the value of a change against its true cost.
Maintain clear communication
Regular meetings between client, architect, and builder help identify issues early before they escalate.
Not all changes are negative. Sometimes better solutions emerge once construction is underway. The key is making informed and deliberate decisions rather than reactive ones.
An experienced builder will clearly explain the cost, programme, and compliance implications so clients can decide whether a change genuinely adds value.
Final Thoughts
Changes during construction are one of the largest contributors to cost overruns, but they are also one of the most controllable.
With thorough documentation, early collaboration, and disciplined decision making, homeowners can protect both their budget and theintegrity of their architecturally designed home.
