Cost guide
What drives the cost of a bathroom.
A bathroom is small, wet and full of trades. Demolition, plumbing, waterproofing, tiling, electrical, cabinetry and fixtures all happen in a room a few metres across, in a fixed order, each trade waiting on the last. This guide explains what moves a bathroom budget, what you control, and the usual mistakes. No figures: your own estimate is free.
A small room with every trade in it
A bathroom is priced like any building work, quantities first: square metres of floor and wall tiled, square metres waterproofed, the number of fixtures and their plumbing points, the electrical points and lights, the metres of cabinetry, the shower screen, the door and the window. Then each quantity gets its price from a supplier offer, a market price or a rate, plus the trade hours to install it. Four things set most of the total.
The first is whether the fixtures move. A bathroom that keeps the toilet, the shower and the basin where they are needs new connections at the same points. One that moves them needs new drainage through the floor, which in a slab means cutting concrete and on a timber floor means working between joists, plus new water runs in the walls. Moving the toilet is the dearest move of all, because its drain needs fall to the sewer. Keeping the layout is the single largest saving in a bathroom.
The second is waterproofing and tiling. Waterproofing is licensed, regulated work and is priced by the square metre of floor and wall it covers; it is not the place to save. Tiling is priced by the square metre of material and by the tiler's hours, and the hours rise with small formats, mosaics, patterns, feature walls and tiling to the ceiling. A floor-to-ceiling tiled bathroom is a different job from one tiled to the wet areas.
The third is the fixtures. Toilet suite, basin and vanity, tapware, shower head and mixer, bath, shower screen, mirror and accessories are each a product with a price and a wide range. A wall-hung toilet or basin hides its plumbing in the wall, which is more work; a freestanding bath needs its own floor waste and tap. The vanity is cabinetry, priced like a kitchen's.
The fourth is the room itself. Demolition and disposal of the old bathroom, the condition of the floor and walls found beneath it, a window or an exhaust fan ducted to outside, lighting, heating, a new door, and making good. In older houses what is under the old tiles is not known until they come off, which is why a bathroom budget carries a contingency and the estimate shows it as its own line.
The finish level then runs across everything you can see: the tiles, the tapware and fixtures, the vanity, the screen and the lighting. In a bathroom, a level change is felt mostly in the tiling and the tapware.
The cost factors, and what you control
| Factor | Why it moves the price | What you control |
|---|---|---|
| Layout | Moving the toilet, shower or basin means new drainage and water runs; the toilet is the dearest to move | Keep the fixtures where they are if you can |
| Waterproofing | Licensed work priced by the area it covers | Only how large the wet areas are; never the quality |
| Tiling | Square metres and the tiler's hours, which rise with small formats, patterns and tiling to the ceiling | Tile format, extent and pattern |
| Fixtures | Each is a priced product; wall-hung and freestanding fixtures add work | Finish level, then product by product |
| Vanity | Cabinetry priced like a kitchen's, plus the basin and benchtop | Size, construction and finish |
| Shower screen | Framed, semi-frameless or frameless, by size | Type and size |
| Ventilation and electrical | Exhaust ducted to outside, lighting, heating, power points | What you add |
| The existing room | Demolition, disposal, the floor and walls found beneath, making good | An inspection; a contingency shown as its own line |
| Finish level | Runs across tiles, tapware, fixtures, vanity, screen and lighting | Economical, Standard, Good or Advanced, then product by product |
Finish levels explained
On Modern GBQ a finish level, Economical, Standard, Good or Advanced, sets a default product on every bathroom line: tiles, tapware, toilet suite, basin and vanity, shower screen, bath, mirror, accessories and lighting. Economical takes the plainest listed product that does the job; Standard the mid-range most bathrooms are built with; Good a step up in material and brand; Advanced premium products and the extra labour some of them need, such as large-format or feature tiles and wall-hung fixtures.
Bathrooms reward spending where hands and eyes go. Tapware and the shower are used every day; the toilet suite and the exhaust fan are not admired. A Standard base with Good tapware and tiles is a common and sensible answer.
Every default can be swapped for a listed alternative, with a photo to judge it by and a short reason recorded, then re-priced as a new version. The finish level never changes the waterproofing or the drainage.
Common mistakes
- Moving the toilet. Its drain needs fall to the sewer, and in a slab that means cutting concrete. Move it only when the layout truly needs it.
- Saving on waterproofing. It is licensed, regulated work and the one thing in a bathroom that must not fail. Spend on the finishes instead.
- Tiling everything, in small tiles. Floor-to-ceiling mosaics are mostly tiler's hours. Decide where tiling stops.
- Choosing fixtures after the plumbing is in. Wall-hung toilets, freestanding baths and shower mixers set where the pipes go. Choose them first.
- Forgetting ventilation and light. An exhaust fan ducted to outside and good lighting are small lines that make the room work.
- Comparing quotes with different inclusions. One includes the fixtures and the electrical, another does not. Approve one scope and have every builder price that.
- Treating the estimate as a quote. It is an estimate for budgeting. What is found under the old tiles is a variation to agree with your builder directly.
Your own figure
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Bathroom questions.
What is the biggest cost in a bathroom?
If the fixtures move, the plumbing. If they stay, usually the tiling and waterproofing, then the fixtures. The estimate prices each as its own lines so you can see your own answer.
Does the estimate include the plumbing and electrical?
Every line prices the material and the trade labour to install it, from trade rates for your locality, with the hours shown. Anything you leave out of the scope is listed under what is not in the price.
Can I see the tiles and tapware before I choose?
Yes. Where the catalogue holds a photo, it appears beside the product and each alternative, so you choose by what it looks like and swap with a reason.
How do I compare a Good and an Advanced bathroom?
Re-price after changing the level and put the two versions side by side. Every version is kept, so the comparison is line by line, not a feeling.
Price the bathroom before you meet a builder.
Free to start. Every line explained.