Define what the quote is buying
A floor-area rate cannot tell you whether a house needs rewiring, a new subfloor or only new finishes. Walk through the property, list the rooms and record what will stay. Separate confirmed work from conditions that still need investigation. The Australian Government’s Your Home renovation guidance supports assessing the existing building and coordinating specialist advice before committing to changes.
This independent teaching project concerns an existing Sydney house with no extension or structural rearrangement. The builder’s packages cover agreed strip-out, private services, wet-area work, preparation and installation. Selected finish products and appliances are owner-supplied. Their supply cost is excluded from the packages; the agreed installation labour is included. Land, borrowing costs and unrelated maintenance are excluded. Write that boundary into the scope rather than relying on “complete renovation”.
Put every price on the same GST basis
Ask each supplier whether the stated amount includes GST and whether GST applies to that supply. ASIC’s MoneySmart explanation distinguishes adding 10% to an exclusive taxable price from extracting one eleventh of an inclusive price. For this calculation, assume both supplies below are taxable supplies by GST-registered businesses. This is not a ruling about every provider or a promise that a homeowner can claim GST credits.
| Supply | Excluding GST | GST | Including GST |
|---|---|---|---|
| Defined builder packages | 95 000 | 9 500 | 104 500 |
| Owner-supplied products and appliances | 18 000 | 1 800 | 19 800 |
| Combined supplies | 113 000 | 11 300 | 124 300 |
The GST component of AUD 104,500 is AUD 9,500, not AUD 10,450. Do not add another 10% to a tax-inclusive quote. The other budget lines below are final amounts, with any applicable tax already included; a planning provision is not itself a tax invoice.
Add the owner’s costs and one named unknown
| Budget line | Amount |
|---|---|
| Builder packages including assumed GST | 104 500 |
| Separate owner purchases including assumed GST | 19 800 |
| Design and documentation | 5 500 |
| Approval and certification allowance | 2 500 |
| Independent progress checks | 1 800 |
| Skip bins, delivery and access outside builder scope | 2 800 |
| Temporary accommodation | 6 500 |
| Allowance for one unpriced subfloor repair | 6 500 |
| Subtotal before contingency | 149 900 |
| Contingency: 10% of builder packages and products | 12 430 |
| Funding provision | 162 330 |
The contingency base is AUD 124,300, the first two lines. Ten per cent is a chosen planning assumption, not an Australian legal requirement or a sufficient buffer for every house. The AUD 6,500 subfloor allowance is a separate identified unknown outside the builder’s agreed preparation. It should be investigated and replaced with a defined scope; the contingency does not make that investigation unnecessary.
Price logistics and disruption explicitly
Record the number and type of skips, access restrictions, expected material streams, delivery handling and who books the receiving facility. NSW EPA guidance explains that operators set their own gate fees. Confirm acceptance conditions and the actual disposal route. Hazardous material requires its own professional assessment and arrangements; do not assume it belongs in a mixed renovation skip.
Ask how long essential rooms will be unavailable and what triggers an accommodation extension. The AUD 6,500 is an assumed total, not a duration guarantee. Check storage, meals and extra travel if relevant. Notify your insurer before work and confirm the property’s cover during renovation, following the NSW insurance guidance. The contractor’s public liability policy and your home policy address different risks.
Replace allowances and credit payments once
If the subfloor repair is accepted for AUD 5,200 final, replace AUD 6,500 rather than adding a second repair line. Keeping the contingency fixed reduces the funding provision to AUD 161,030. Reconsider the contingency if the investigation reveals a broader issue; an arithmetic saving alone does not establish that the remaining risk has fallen.
Against the original AUD 162,330 plan, AUD 20,000 already paid for included items leaves AUD 142,330 still to fund, including the unused contingency. The deposit is part-payment of a contract, not an additional project cost. Track unpaid commitments, refundable amounts and money actually available separately. An unused contingency is a provision, not evidence of cash in the bank.
Keep the plan usable after the first quote
- Give each bidder the same measured scope and purchasing split.
- Record inclusions, exclusions, GST status and quotation validity.
- Resolve important investigations before fixing the build scope.
- Link purchases and staged claims to realistic cash dates.
- Replace provisional figures and record omissions when changes are agreed.
- Review the whole forecast before approving a new commitment.
Reno Pro can organise stages, purchases and recorded payments around this plan. Keep accepted quotes, drawings and inspection records alongside the figures. A useful budget explains what the owner must fund and why; it remains useful when a supplier, selection or sequence changes.
Sources, date and scope
- ASIC MoneySmart — GST calculator
- Australian Government, Your Home — Renovations and additions
- NSW EPA — Household building and renovation
- Building Commission NSW — Insurance requirements for contractors working on your home
Checked on 19 October 2026. Worked projects are in Sydney, NSW, unless stated otherwise. NSW rules are not national rules. All dollar amounts are Australian dollars (AUD); worked costs, quantities, margins and contingency percentages are invented teaching assumptions, not market prices, quotations or prescribed reserves. Each article describes a separate project. GST treatment is stated for the example; final amounts already include any applicable tax. Check the property, current approvals, insurance and contract with the appropriate professionals.