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About this tool
Build a room-by-room renovation budget with a quality tier, professional fees, GST on works contracts and a contingency buffer.
A renovation budget planner prices each room on its own rate per square foot and then adds the layers a headline quote usually leaves out. Room cost is area × rate × a quality multiplier, on top of which sit designer or architect fees, a contingency buffer of the 10–15% conventionally allowed in construction budgeting, and GST at 18% where a registered contractor bills the job as a works contract. The result is a grand total, a cost per square foot, and the monthly saving needed before work starts.
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Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Wet areas carry plumbing and waterproofing costs that a single flat rate hides.
Fees, contingency and GST are applied in the right order, so the total is what you actually pay.
A stated buffer means a hidden leak or an out-of-level floor does not become a mid-project loan.
Yes, when a registered contractor carries out the job it is a works contract, taxed as a composite supply of services at 18%. If you buy the materials yourself and pay only for labour, GST sits inside each material's own rate instead — cement, tiles and paint are taxed at their own notified rates. Rates change, so confirm the current position with your contractor or a tax professional.
10% of the project cost is the usual starting point and 15% is prudent for an older property, because opening up walls and floors regularly reveals wiring, plumbing or damp that was not in the scope. Set it before signing, not after the first surprise.
Wet areas carry work that dry rooms do not — plumbing runs, waterproofing, electrical points for appliances, counters, and cabinetry that is fabricated rather than bought. A kitchen or bathroom commonly costs two to three times a bedroom on a per-square-foot basis, which is why one blended rate across a flat produces a misleading total.
Professional fees on a residential renovation are typically quoted as a percentage of project cost, commonly in the 5–10% range, though some designers charge a flat fee or a per-square-foot rate instead. Ask which model is being used and whether site supervision is included, because that changes what the percentage buys.
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