Timber and plumbing rises offset plasterboard price cuts in September
New Zealand construction costs rose again in September, with trade rates up an average of 0.2%, even though GIB and several other common building materials became cheaper. That's according to QV CostBuilder's latest monthly update.
QV CostBuilder quantity surveyor Martin Bisset said there was no single dominant cost driver this month, with many products moving at once.
Plasterboard down, timber up
Plasterboard linings fell 0.4%, led by a 1.9% average drop in GIB products. Other categories climbed. Plumbing rose 0.8% and waterproofing 1.6%.
Timber was a notable source of upward pressure. Structural timber rose an average of 4.4% across the six centres tracked, timber joists climbed 5.2%, and interior and exterior grade plywood cladding increased 5.6%. Diesel rose 2.3%, a smaller move than some seen earlier in 2026. Some formwork rates rose 12.5%, and fire retardant roof underlay and wall wrap rose 12%.
Bisset said the GIB reduction was welcome given how widely the product is used, but cautioned against reading too much into it.
"But this month is also a good reminder that construction costs almost never move neatly in one direction," Bisset said.
He said timber and related products were used throughout residential construction.
"So even when something as familiar as GIB gets cheaper, that doesn't necessarily mean the overall cost of building is coming down," Bisset said.
Activity improves as cost pressures linger
Bisset said cost growth remained relatively modest overall, even as building activity picks up. Stats NZ figures show construction activity rose 2.7% in the June 2026 quarter, its largest quarterly gain since June 2023, with residential building contributing to the increase.
The pipeline is also growing. Stats NZ data shows 41,268 new homes were consented in the year ended August 2026, up 21%.
Bisset said the pickup in activity had not led to broad-based cost escalation, although pressures had not gone away.
Westpac takes a more cautious view. Senior economist Satish Ranchhod listed a pickup in building costs, alongside higher interest rates and a soft housing market, among the headwinds facing residential construction.
Bisset said the mixed movements had practical implications for budgeting.
"For anyone budgeting a project, that means it still pays to allow for movement rather than assume costs will stay exactly where they are," Bisset said.
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