Most renovation budgets in Perth fail in one of three ways. They don’t include contingency. They don’t account for the full scope of what a renovation involves. Or they’re set before enough design work has been done to know what the renovation actually costs.
None of these failures are the homeowner’s fault — the renovation industry rarely explains budgeting with the clarity that this decision deserves. A bathroom renovation budget that covers tiles but not waterproofing, tiling labour, plumbing, electrical, and project management is not a renovation budget. It’s a materials budget. The gap between those two numbers is where renovations go over budget.
This article covers how to build a renovation budget that reflects what a Perth renovation actually costs in 2026 — including the components most homeowners underestimate, the contingency amounts appropriate for different types of homes, and the cost of decisions that seem small at the time.
Budget Component | Commonly Overlooked? | Notes |
Strip-out and demolition | Sometimes | Disposal costs, skip hire, and labour for removing existing fixtures and finishes. $800–$3,000 for a bathroom. |
Waterproofing | Often | AS 3740:2021 compliant membrane, inspection, and certification. $1,200–$2,500. Non-negotiable. |
Trade labour — tiler | Partially | Labour separate from tile supply. $35–$55/m² for laying, not including materials. |
Trade labour — plumber | Often | Both rough-in (before tiling) and fitoff (after cabinetry). Two separate site visits. |
Trade labour — electrician | Often | Rough-in and fitoff, plus Certificate of Compliance. Always a licensed electrician in WA. |
Project management | Frequently | The coordination of trades, scheduling, client communication, and defect management. Included in a House & Co fixed-scope quote. Not included in many others. |
3D design | Frequently | The design work before any trade is booked. Included at House & Co. Sometimes charged separately at $1,500–$4,000. |
Council permits (if required) | Often | $800–$2,500 in council fees, plus the time cost of the application process (6–12 weeks). Permit cost separate from the builder's margin. |
Asbestos removal (if present) | Very often | $2,000–$8,000 depending on extent. Not speculative — it's either there or it isn't, and a pre-renovation inspection can tell you. |
Replumbing (if galvanised) | Very often | $3,000–$7,000 for a bathroom or kitchen zone. A pre-renovation plumbing inspection can identify this before the quote. |
Variations — client-initiated | Very often | The cost of changing your mind mid-build. Tile substitutions, cabinetry changes, added features. See below. |
Property Type | Recommended Contingency | Reason |
Post-2000 Perth home, no prior renovation | 8–10% | Low risk of hidden surprises. Modern construction, known materials, standard compliance. |
1980s–2000 Perth home, brick veneer | 10–12% | Some risk of galvanised plumbing, older wiring. Prior renovation quality variable. |
1960s–1980s Perth home — first major renovation | 15–18% | Asbestos likely in wall and ceiling linings. Galvanised plumbing probable. Electrical likely non-compliant in places. Budget for all three. |
Pre-1960 Perth character home (double-brick, timber floors) | 18–22% | Highest risk profile. Asbestos almost certain. Original plumbing and electrical throughout. Possible termite damage in subfloor or wall framing. Structural surprises in older additions. |
Any home — major structural work (extensions, load-bearing wall removal) | +5% on above | Structural surprises add cost that's hard to anticipate without opening up. Add 5% above the base contingency for any project involving structural work. |
A budget built on an estimate is not a budget — it’s a best guess. The starting number for any renovation budget should be a fixed-scope quote that specifies every trade, every material, and every element of the project. That is the base.
Using the table in Section 03 above, calculate the appropriate contingency for your property. Add this to the fixed-scope quote to get the total budget. This is the amount you need available — not the amount you expect to spend.
If your home is pre-1990, organise an asbestos assessment and a plumbing inspection before the renovation company visits. The results change the quote you receive — and prevent discoveries from becoming variations. Known issues built into a fixed-scope quote cost less than discovered issues addressed as variations.
The 3D design process exists to bring every decision to the surface before work begins. Tile selections, hardware specifications, cabinetry finishes, benchtop material — every decision made and approved in design costs nothing to change. Every decision changed after the build starts costs time and money.
A kitchen renovation typically means 4–7 weeks without a functional kitchen. An allowance for dining out, takeaway, or a temporary kitchen setup is a real cost that often isn’t included in the renovation budget. For a family of four, 6 weeks of alternative eating arrangements can add $2,500–$5,000 to the real cost of a kitchen renovation.
Scope creep — the gradual expansion of a renovation’s scope from what was originally agreed — is the most common source of budget overrun in projects that started with a genuinely fixed-scope quote. It’s usually not the renovation company’s fault. It happens because decisions that seemed settled at the design stage are revisited once the build is underway, and because “while you’re there” is one of the most expensive phrases in renovation.
The tiles are ordered, the project is running. A new tile is spotted on social media. It would look better. Can the tiles be changed? Yes — but the ordered tiles need to be returned (if possible) or written off as a cost, new tiles ordered (possibly with a different lead time), and the tiler’s schedule may need to shift. A tile change mid-build that costs the tiles themselves may cost an additional $1,500–$4,000 in total including wastage, re-ordering, and schedule impact.
“While you’re in there, can we add a heated floor?” Adding a heated floor after the rough-in electrical is complete means the electrician returns for an additional visit, the thermostat is wired in, and the tile setter installs the heating mat. This is $1,500–$3,000 that would have cost $800–$1,200 if it had been in the original scope. The later a decision is made, the more it costs.
The standard vanity in the specification is replaced with a custom joinery vanity. The custom joinery adds 3 weeks to the manufacturing lead time. The project is delayed. The trades that were scheduled for the following fortnight move to the next available date. The schedule impact of a $3,000 upgrade to a vanity costs $1,500 in delay costs and rescheduling. The total cost of the upgrade: $4,500.
The 3D design process at House & Co exists specifically to prevent mid-build changes. When every decision is made and approved in 3D before the build starts, the temptation to change mid-build is significantly reduced — because the client has already seen the finished result and approved it. The 3D process does not eliminate changes, but it dramatically reduces them. And revisions during design cost nothing. Revisions during construction cost significantly more.
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