The main cost drivers are the size of the room, whether you change the layout or move plumbing, the condition of the substrate and required waterproofing, the tile area and tile type, your choice of fixtures and joinery, and site access. You can control costs by keeping the existing layout where practical, choosing standard-sized tiles and mid-range fixtures, and setting a clear scope before work begins. A contingency for hidden issues is still advisable.
01Bathroom size and the amount of surface area
A larger bathroom generally costs more because there is more wall and floor area to waterproof, tile and finish. More surface area means more materials, longer tiling time and more labour across every trade. But size is not the only driver; a small bathroom with premium fixtures and a complex layout can cost more than a basic larger bathroom.
The number of wet areas and fixtures also matters. A bathroom with a separate shower, freestanding bath, double vanity and toilet has more plumbing points, more waterproofing details and more fit-off work than a simple three-piece bathroom. Keeping the same fixture count and footprint usually makes the job more predictable.
- Wall and floor area drive waterproofing and tiling quantities.
- Adding a bath or double vanity increases rough-in and fit-off labour.
- Very small rooms can be slower per square metre due to tight access.
02Layout changes and moving plumbing
Moving a toilet, basin or shower drain is one of the fastest ways to add cost. Relocating a toilet or floor waste on a concrete slab often requires cutting into the slab, re-running drainage and then repairing and re-waterproofing. On a timber floor, the plumber may need to work around joists or run new pipes between levels.
If the existing layout works, keep the toilet, shower and vanity close to their current water and waste connections. Some movement along the same wall, such as shifting a basin within a vanity run, is usually less disruptive than moving a fixture to the opposite side of the room. All plumbing and drainage work must be done by a licensed plumber.
- Leaving the toilet and vanity on existing connections reduces plumbing works.
- Moving a floor waste or shower drain on a slab adds cutting and patching.
- Drainage and water supply must comply with the NCC and be installed by a licensed plumber.
03Waterproofing and substrate preparation
Waterproofing is not an area to cut. The Building Code and AS 3740 set out where bathroom waterproofing is required, including the shower recess, bathroom floor and walls around wet areas. The condition of the existing walls and floor matters: if old tiles have been removed and the substrate is uneven, cracked or water-damaged, the walls may need re-sheeting or the floor may need a leveling screed.
A proper waterproofing job includes priming, membrane application, bond breakers at floor/wall junctions and a water stop at the shower entry. The shower floor must have a fall to the waste. These details take time and must be done by a competent person. A cheap waterproofing scope can lead to leaks that damage adjoining rooms and cost far more to fix later.
- All wet areas must be waterproofed to the required heights.
- Uneven or damaged substrates add preparation and re-sheeting costs.
- Water stops and bond breakers are needed at junctions and shower entries.
04Tiling extent and installation complexity
Tile cost depends on the area to be tiled and the tile type. Floor-to-ceiling tiling uses more material and more setting time than tiling only the wet walls to 2100mm or the splash zones. Large-format tiles can be quicker to lay over large flat areas, but they are heavy and need a very flat substrate, which may require extra preparation.
Small mosaics, borders and feature bands increase the number of cuts and setting time. Rectified-edge tiles with narrow grout lines also require careful work. For bathroom floors, choose a tile with an appropriate slip rating for wet areas. Adhesive, grout, trims and sealers all add to the installed cost beyond the tile price.
- Floor-to-ceiling tiling increases tile and labour quantities.
- Mosaics and complex patterns take longer to set.
- Large-format tiles often need extra substrate flattening.
05Fixtures, tapware and vanity joinery
Product selection can shift the budget more than any choice except layout changes. A basic close-coupled toilet, standard basin and mixer tap cost less than a wall-hung toilet with in-wall cistern, a stone basin and a rain shower with diverter. Tapware finishes such as brushed nickel or matte black often cost more than chrome, and matching all accessories adds up.
Vanity joinery is another variable. A stock vanity is economical, while a custom vanity can be built to fit an awkward space and include better drawer hardware, stone tops and integrated basins. If storage or use of space is important, custom joinery can be worth it, but it will increase the cabinetry component. Decide which products matter most and keep others standard.
- Wall-hung toilets need an in-wall cistern and extra framing.
- Custom vanities cost more than standard units but improve space use.
- Multiple shower outlets require more plumbing and hot water capacity.
06Site access, existing conditions and trade coordination
Where the bathroom sits in the building affects cost. A ground-floor room with direct external access is easier to service than an upstairs bathroom or an apartment with lift and common area restrictions. Tradespeople may need to carry materials and remove waste over longer distances. Older homes may contain asbestos in wall sheeting or flooring, which must be removed by a licensed asbestos removalist before renovation work proceeds.
Good trade coordination prevents delays and defects. A bathroom renovation runs from strip-out and rough-in plumbing and electrical, to sheeting and waterproofing, tiling, then fit-off of fixtures. If you are managing separate trades yourself, any gap or sequence error can cause rework. A renovation company with an in-house team can reduce the number of contractors you have to coordinate.
If you are planning a bathroom renovation in Melbourne and want to see products and discuss how these factors apply to your home, visit Baroco Interior Innovations at 21/105-111 Ricketts Road, Mount Waverley. The showroom has toilets, tapware, vanities, basins, showers and baths on display, and written quotes are provided after a measure. Call 0426 520 859 ahead of your visit.
- Difficult access or upper-floor jobs can add labour and waste removal costs.
- Asbestos removal, if found, is a licensed trade and a separate budget item.
- Poor trade sequencing can cause downtime and moisture issues.
Planning this for your home? See how we design, supply and build it, or visit the Mount Waverley showroom.
Bathroom renovations · Try the AI bathroom previewRelated questions
Still unsure? Call 0426 520 859 and talk to someone who actually installs this stuff.
Does a larger bathroom always cost more to renovate?
Generally yes, because there is more floor and wall area to waterproof, tile and finish. However, a small bathroom with a rearranged layout and high-end fixtures can cost more than a larger bathroom kept in its existing footprint with basic materials.
Can I save money by moving the toilet or shower to a different wall?
Usually no. Moving plumbing and drainage is one of the quickest ways to add cost, especially on a concrete slab or upper floor. Keeping the toilet and shower on their existing connections is often cheaper unless the layout is unworkable.
Do I need a licensed plumber and electrician for a bathroom renovation?
Yes. In Victoria, plumbing and electrical work must be done by licensed tradespeople. Waterproofing must also be done by a competent person and meet AS 3740. A licensed builder or registered practitioner should manage the project to ensure compliance.
How can I control costs without cutting corners on waterproofing?
Keep the existing layout if it works, choose mid-range tiles in standard sizes, limit feature walls, and decide all fixtures before works start. Make sure your quote includes full waterproofing of the shower and floor, and keep a contingency for hidden issues.
