Tiling a splashback behind a freestanding bath is a satisfying DIY project that can dramatically lift the look of your bathroom. Because the area sits in a wet zone, getting the waterproofing and substrate right is just as important as laying the tiles neatly. Follow these steps and you'll end up with a professional-looking result that meets the NZ Building Code.
Plan the Layout Before You Touch a Tile
Start by deciding on your tile size, pattern and the height of the splashback. A common approach is to run tiles from the floor (or a skirting line) up to around 300–600 mm above the rim of the bath, though some homeowners go full wall height for a dramatic effect.
- Measure the wall width and work out a centred layout so you don't end up with tiny slivers at each end.
- Use a spirit level and pencil to mark a true horizontal datum line — this is your starting reference.
- Dry-lay tiles on the floor first to check your pattern and spacing before committing to adhesive.
Prepare the Substrate Properly
The surface behind a freestanding bath is a wet area under NZ Building Code clause E3 (Internal Moisture). The substrate must be solid, flat and suitable for tiling.
- Plasterboard (standard GIB board) is not suitable in wet areas. Use GIB Aqualine or a fibre-cement sheet such as James Hardie Scyon or HardieBacker as your tile backing board.
- Fix the board firmly to studs, fill screw holes and tape joints with fibreglass mesh tape and a suitable base coat.
- Check the wall is flat — high spots can be sanded back, low spots built up with tile adhesive or a levelling compound.
Waterproof the Wet Zone
This step is non-negotiable. Even though a freestanding bath splashback sees less water than a shower, it still needs a waterproof membrane applied before tiling, particularly at the bottom where the bath meets the wall.
- Apply a liquid membrane (such as products from Ardex or Mapei) to the full tiled area, paying extra attention to corners and the junction between wall and floor.
- Bed fibreglass reinforcing tape into corners while the membrane is wet, then apply a second coat.
- Allow to cure fully per the manufacturer's instructions before tiling.
- Check BRANZ guidance on wet area construction if you're unsure about membrane requirements.
Choose the Right Adhesive and Tiles
For a wet area, use a polymer-modified tile adhesive rated for wet zones — standard white powder adhesive is not sufficient on its own.
- Products from Ardex, Mapei or Sika are widely available at trade suppliers and Mitre 10 or Bunnings.
- Use the notched trowel size recommended for your tile format — larger tiles need a larger notch.
- For a splashback, porcelain, ceramic or natural stone tiles all work well. Natural stone needs sealing before and after grouting.
Laying the Tiles Neatly
Setting Out
- Start from your datum line and work upward.
- Use tile spacers (1–3 mm for a modern look, wider for a rustic feel) to keep joints consistent.
- Back-butter large tiles in addition to combing adhesive on the wall — this ensures full coverage and prevents hollow spots.
Cutting Tiles
- A wet saw (tile saw) gives the cleanest cuts, especially for porcelain. These can be hired from Bunnings or Mitre 10.
- A score-and-snap cutter works fine for straight cuts on ceramic tiles.
- Measure and cut edge tiles carefully — neat cuts at the sides make a big difference to the finished look.
Keeping Things Plumb and Level
- Check every few rows with your spirit level.
- Don't rely on the bath rim or floor as a level reference — they rarely are.
Grouting and Sealing
Allow the adhesive to cure for at least 24 hours (check the product datasheet) before grouting.
- Use a flexible, waterproof grout for wet areas. Epoxy grout is highly durable but harder to work with; cement-based flexible grout is more DIY-friendly.
- Mix grout to a smooth, lump-free consistency and work it into joints with a rubber float at a 45° angle.
- Clean excess grout off tile faces with a damp sponge before it hardens, rinsing frequently.
- Once cured, apply a grout sealer to cement-based grout to protect against staining and moisture.
The Bath-to-Wall Junction
This is where many DIY jobs go wrong. Never grout the joint between the bath rim and the tiles — this joint must be filled with a flexible silicone sealant to allow for movement.
- Use a sanitary-grade silicone in a matching colour.
- Tape both edges with painter's tape, apply the silicone, smooth with a wet finger or tool, then remove the tape before it skins over.
- Sika and other brands offer mould-resistant bathroom silicones suitable for this purpose.
When to Call a Professional
While tiling itself is not restricted work in NZ, some related tasks are:
- Any changes to plumbing (moving tap outlets, waste pipes) must be carried out by a licensed plumber registered with the Plumbers, Gasfitters and Drainlayers Board.
- Electrical work near the bath (lighting, heated towel rails, underfloor heating) is restricted work under the Electrical Workers Registration Board rules — always use a registered electrician.
- If you're unsure about waterproofing requirements or substrate condition, consult a Licensed Building Practitioner or an experienced tiler. You can find qualified local tilers on tradedirectory.co.nz.
- Building consent is generally not required for a like-for-like splashback tile job, but always confirm with your local council if you're making structural changes.
Site Safe
SiteWise
BCITO Qualified
