How to Estimate a Bathroom Renovation
Estimating a bathroom renovation means pricing several distinct trade packages against a small footprint — demolition and strip-out, waterproofing, floor and wall tiling, plumbing rough-in and fit-off, electrical, and prime cost (PC) items for tapware, the vanity and fixtures — then adding a margin that reflects how little room a small fixed-price job has to absorb a mistake.Because a bathroom is small, every line item carries more relative weight than it would on a larger job. A missed waterproofing allowance, an underestimated tiling wastage figure, or a vague PC item can turn a quote that looked profitable into one that isn’t, which is why experienced estimators price bathrooms line by line rather than by a single rate per square metre.
Key takeaways
- Break a bathroom renovation into separate priced packages — demolition, waterproofing, tiling, plumbing, electrical and PC items — rather than quoting a single lump sum.
- Waterproofing and tiling are both measured in square metres from the actual floor and wall plan, with tiling needing a higher wastage allowance than an open room because of cuts around fixtures.
- Prime cost (PC) items let you quote a fair fixed price for tapware, the vanity and other fixtures before the client has chosen them, protecting your margin if their selection costs more than the allowance.
- Small fixed-price bathroom jobs run on tight margins, so latent conditions behind old walls need a deliberate, visible allowance rather than being absorbed silently into another trade.
- My Trade Hub speeds up bathroom quoting by measuring tile and waterproofing areas from your uploaded plans and applying your own editable rates automatically, producing a priced tender 60–75% faster than doing it by hand.
What goes into a bathroom renovation estimate
A bathroom renovation estimate is really several smaller estimates stitched together — demolition, waterproofing, tiling, plumbing, electrical, and the client-selected fixtures — each priced against its own quantity and rate, then combined with preliminaries and margin.
Unlike a new build, where trades often run in parallel across a large area, a bathroom is a single small room where every trade works around the others in sequence. That keeps the quantities modest but makes the risk allowance proportionally bigger — missing one line item has a much larger relative impact on profit than on a whole-house job.
- Demolition and strip-out — removing existing tiles, fixtures and, where needed, wall linings
- Waterproofing — membrane to floor and wall areas, priced by the square metre
- Floor and wall tiling — measured in square metres, priced with a wastage allowance
- Plumbing rough-in and fit-off — supply, drainage and fixture connection
- Electrical — lighting, exhaust fan and safety-switch compliance
- PC items — tapware, vanity, toilet suite and shower screen or bath
- Preliminaries and margin — site protection, waste removal and profit
Demolition, strip-out and what’s hiding behind old walls
Demolition sets the scope for everything that follows, so it needs its own line item priced by the square metre of floor and wall being stripped — plus a deliberate allowance for the latent conditions that often turn up once old tiling, sheeting or waterproofing comes off.
A typical scope removes the existing wall and floor tiles, the bath, vanity and toilet, and any wall linings back to the stud or masonry, plus waste disposal. In an older home this can uncover fibro sheeting, leak-affected timber, or plumbing runs that don’t match the original drawings — none of which are visible until the walls are open. Pricing demolition as its own item keeps these discoveries visible as a variation rather than a silent hit to the margin on another trade.
- Strip-out of existing tiles, fixtures and wall linings back to stud or masonry
- Waste removal and disposal priced separately from labour
- A named allowance for conditions that can’t be seen until the walls are opened
Waterproofing: why it earns its own line item
Waterproofing is measured in square metres of floor and wall area that will be tiled or exposed to water, and it belongs in the estimate as its own item because it’s both a compliance requirement and one of the most common sources of defect callbacks in bathroom work.
Under AS 3740, the whole floor generally needs a membrane, plus wall areas around showers and baths to a specified height. It’s priced by area rather than folded into tiling because membrane, primer and flashing don’t scale the same way tiling does — and because a bathroom that fails inspection, or leaks after handover, costs far more in rework than the line item ever saved.
Why waterproofing deserves its own line
Waterproofing failures are among the most common and expensive defects in Australian residential bathroom work. Pricing it as a clear, itemised part of the quote — rather than bundling it into tiling — protects both the client’s compliance position and your margin if a callback ever happens.
Floor and wall tiling: measuring area and allowing for wastage
Tiling is priced from the measured floor and wall area in square metres, with a wastage allowance added on top to cover cuts, breakages and pattern matching — and that allowance is usually higher in a bathroom than in an open room because of the cuts needed around fixtures, niches and corners.
A straightforward floor lay might only need a modest wastage allowance, but a bathroom with a niche, a hob and angled cuts around a toilet can need considerably more to avoid running short mid-job. The table below shows how a bathroom renovation quote is typically broken into line items — the figures are illustrative only; every real job should be quoted from your own current rates library.
| Line item | Typical unit | Example rate | Example subtotal |
|---|---|---|---|
| Demolition & strip-out | m² floor + wall | Illustrative example | Illustrative example |
| Waterproofing | m² | Illustrative example | Illustrative example |
| Floor tiling (incl. wastage) | m² | Illustrative example | Illustrative example |
| Wall tiling (incl. wastage) | m² | Illustrative example | Illustrative example |
| Plumbing rough-in | item | Illustrative example | Illustrative example |
| Plumbing fit-off | item | Illustrative example | Illustrative example |
| Electrical | item | Illustrative example | Illustrative example |
| PC items allowance | provisional sum | Client-selected | Illustrative example |
| Preliminaries & margin | % of subtotal | Illustrative example | Illustrative example |
Plumbing rough-in and fit-off
Bathroom plumbing is usually priced as two separate stages — rough-in, which moves or extends supply and drainage before the walls are lined, and fit-off, which connects the tapware, mixer and fixtures once tiling is complete — because they happen at different points in the program and carry different risk.
Rough-in is where relocating a toilet or shower outlet, or working around old cast-iron or galvanised pipework, adds cost a like-for-like fit-out wouldn’t need. Fit-off is more predictable once the PC items are selected, but still needs its own allowance for testing, sealing and making good around each fixture.
Electrical: lighting, exhaust and safety compliance
Bathroom electrical work is a smaller line item than tiling or plumbing, but it still needs pricing as its own scope — lighting points, an exhaust fan or upgrade, and any switchboard or safety-switch work needed to meet current wiring rules for wet areas.
Exhaust fan capacity and placement affect how well the waterproofing and finishes hold up over time, so it’s worth pricing as a genuine line item rather than a rough allowance — particularly if the existing switchboard needs additional safety switches to bring the circuit up to standard.
PC items and why small fixed-price bathrooms run on tight margins
Prime cost (PC) items let you quote a bathroom renovation before the client has chosen their tapware, vanity, toilet suite or shower screen — and getting them right matters more here than on a larger job, because a bathroom renovation is usually quoted as a single fixed price with very little room to absorb a miscalculation.
A PC item states a provisional allowance for each client-selected fixture, and the final price adjusts to match what they actually choose. Without that, a gap between a basic and a designer vanity either comes out of your margin or turns into a dispute at handover. Because a bathroom job runs to a modest total, a single under-priced line — a missed PC allowance or an hour of unplanned rework — represents a much bigger share of the total than the same miss would on a whole-house renovation.
- State a clear PC allowance for tapware, vanity, toilet suite and shower screen, and get client sign-off against it
- Price demolition, waterproofing, tiling, plumbing and electrical as separate line items rather than one lump sum
- Build preliminaries and margin in deliberately — small jobs have less room to absorb an under-priced line
How My Trade Hub speeds up bathroom renovation quoting
My Trade Hub speeds up bathroom renovation estimating by measuring tile and waterproofing areas directly from your uploaded plans, applying your own editable rates automatically, and handling PC items properly — so a fully priced, professional quote comes together in a fraction of the time it takes by hand.
Upload the plan and My Trade Hub’s automated takeoff measures the floor and wall areas so you’re not scaling a PDF with a ruler for a job this small. Your rates library — the labour, material and plant prices you’ve already built up — applies to those quantities automatically, and every rate stays editable, so a bathroom with awkward cuts or a premium tile still gets priced the way you’d price it yourself. PC items for tapware, vanities and fixtures are handled as their own line so the client sees a clear allowance rather than a guess buried in the total. The result: preparing a priced bathroom renovation tender with My Trade Hub is 60–75% faster than building the same quote manually, without losing the detail that keeps a small, tight-margin job profitable.
- Automated takeoff measures floor and wall tile areas from your uploaded plans
- Editable rates library applies your own labour, material and plant prices automatically
- PC items for tapware, vanities and fixtures are itemised, not buried in the total
- A full priced quote or tender document is ready to send 60–75% faster than manual pricing
Frequently asked questions
How do I estimate a bathroom renovation?
You estimate a bathroom renovation by pricing it as separate packages — demolition and strip-out, waterproofing, floor and wall tiling, plumbing rough-in and fit-off, electrical, and PC items for tapware, the vanity and fixtures — each measured against its own quantity, then adding preliminaries and a margin that reflects the tight, fixed-price nature of a small job.
How much should I allow for waterproofing in a bathroom quote?
Waterproofing should be measured in square metres of the actual floor and wall area being treated, per AS 3740, and priced as its own line item rather than folded into tiling. Use your own current rates library for the actual figure — it varies by membrane system and site conditions.
What is a PC item in a bathroom renovation quote?
A PC item, or prime cost item, is a stated provisional allowance for a fixture the client hasn’t chosen yet — typically tapware, the vanity, the toilet suite or a shower screen — with the final price adjusted once they make their selection, so the fixed-price part of the quote stays fair to both sides.
How much tiling wastage should I allow for a bathroom?
Bathroom tiling generally needs a higher wastage allowance than an open room, because of the cuts required around niches, hobs, corners and fixtures. The exact figure depends on the tile size, pattern and layout, so it should be set in your rates library and applied consistently rather than guessed per job.
Why do bathroom renovation quotes need a tighter margin than expected?
Bathroom renovations are usually quoted as a single small fixed price, so a missed PC allowance, an underestimated wastage figure, or unplanned rework has a much bigger relative impact on profit than the same miss would on a larger job — which is why margin needs to be a deliberate, visible allowance rather than whatever is left over.
What should be included in a bathroom renovation quote?
A bathroom renovation quote should include demolition and strip-out, waterproofing, floor and wall tiling with a wastage allowance, plumbing rough-in and fit-off, electrical work including the exhaust fan, PC items for client-selected fixtures, and preliminaries and margin.
How can I quote a bathroom renovation faster?
You can quote a bathroom renovation faster by using software that measures tile and waterproofing areas from your uploaded plans and applies your own editable rates automatically. My Trade Hub does this and handles PC items as their own line, producing a priced tender around 60–75% faster than pricing the same job manually.
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