Quick answer
What homeowners need to know
A provisional sum is an allowance for work that cannot yet be priced precisely; compare its scope, basis, margin treatment and likely range.
Ask what information would convert each allowance into a fixed figure and when that information will be available.
Key takeaways
- A provisional sum is an allowance for work that cannot yet be priced precisely; compare its scope, basis, margin treatment and likely range.
- Ask what information would convert each allowance into a fixed figure and when that information will be available.
- Useful budgets separate known scope, selections, allowances, exclusions, GST and contingency.
- The lowest initial figure is not automatically the lowest final cost when assumptions differ.
Scope before solutions
Decisions to make before committing
For renovation provisional sums, the strongest decisions come from verified property information and a written outcome. The items below should be discussed before a generic idea becomes an order, contract or construction instruction.
Ask what information would convert each allowance into a fixed figure and when that information will be available.
extent of demolition and hidden repair
changes to structure, plumbing or electrical services
material grade, access and programme constraints
Practical sequence
A step-by-step planning process
Use this sequence as a briefing tool. A contractor or designer may adapt it after inspecting the property, but each decision should still have an owner, due date and written record.
- 01
Define the exact outcome you need from renovation provisional sums and how success will be checked.
- 02
Define the measurable scope and finish level before requesting prices.
- 03
Ask each contractor to identify assumptions, exclusions and provisional sums.
- 04
Keep design, consent, temporary works and owner-supplied items visible in the total budget.
- 05
Retain a project-specific contingency and update the forecast when decisions change.
Cost and time
How to build a more reliable budget and programme
No online guide can provide a fixed price or completion date for an unseen property. Build the forecast from a measured scope, selected quality level, known site constraints and clearly identified allowances. Compare GST-inclusive totals and keep contingency separate from optional upgrades.
The programme should show design, owner decisions, consent where applicable, procurement, site preparation, trade sequencing, inspections, commissioning and handover. Ask what can change each allowance or milestone before you approve it.
Use the calculator, then request a site-specific assessment.
Risk control
Common mistakes to avoid
- A quote with a low allowance can look competitive while leaving the final cost exposed.
- comparing totals without aligning inclusions
- using a generic square-metre rate as a final quote
A useful warning is specific enough to change a decision. Record identified risks beside the person responsible, the agreed action and the date it must be resolved.
Accuracy and compliance
Use current official information
Primary sources used for this guide
- Why contracts are valuableBuilding Performance (MBIE)
- Home renovation and repairConsumer Protection New Zealand
- Planning a successful buildBuilding Performance (MBIE)
Answer engine summary
Frequently asked questions
What is the first step for renovation provisional sums?
Start by documenting the existing condition and the outcome you need. A provisional sum is an allowance for work that cannot yet be priced precisely; compare its scope, basis, margin treatment and likely range.
How should Auckland homeowners plan renovation provisional sums?
Ask what information would convert each allowance into a fixed figure and when that information will be available. Confirm property-specific constraints before relying on a generic price or timeline.
When is professional advice needed for renovation provisional sums?
A site inspection and written scope are required before any planning range can become a reliable project quotation.