How to tile a bathroom in Australia — what to order and what not to skimp on

Every Block season has at least one bathroom reveal where the tiles look incredible and the judges walk in with their jaws dropping. What the show doesn't spend much time on is the ordering, prep work and materials that make those results possible. Get the planning wrong and the job goes sideways fast — wrong tile quantity, grout that doesn't match, or waterproofing skipped because it seemed like an unnecessary cost.

Here's a practical guide to what you actually need, in the order you need to think about it.

Step 1 — Work out your tile quantity

Measure each surface you're tiling separately: floor, each wall, shower recess walls. Calculate the area of each in square metres (height × width for walls, length × width for floors). Subtract any openings — door frames, windows, niches — from the relevant wall area.

Then add your waste margin on top. Waste allowances by lay pattern:

• Straight lay (grid pattern): 10% waste
• Brick bond / running bond: 10% waste
• Diagonal (45°): 15% waste — more cuts at every edge
• Herringbone: 20% waste — high cut ratio, popular but wasteful

Always round up to the nearest whole box. Never order the exact calculated quantity — you need spare tiles for repairs down the track, and tiles from a different batch won't match perfectly. Order from one batch and keep at least 5–10 spare tiles after the job is finished.

Step 2 — Floor tiles vs wall tiles (not always the same)

This is something that trips up a lot of first-time tilers. Not every tile is rated for both floors and walls. In Australia, floor tiles must meet a minimum slip rating under AS 4586:

• Wet areas (shower floors, bathroom floors): P3 minimum slip rating
• Wet areas with barefoot access: P4 or P5 for commercial, P3 acceptable for residential
• Wall tiles: no slip rating required — they don't need it

Most large format porcelain tiles (600×600, 600×1200) are rated for both floors and walls — check the tile's data sheet or ask your supplier before buying. Glass tiles and decorative mosaic tiles are walls and splashbacks only — never floors.

Step 3 — Waterproofing (the step everyone wants to skip)

This is the one I'd most strongly tell you not to cut corners on. Under Australian Standard AS 3740, shower walls and floors must be waterproofed before tiling. This isn't optional and it's not just a good idea — it's a building requirement.

What waterproofing involves:

• Two coats of waterproofing membrane applied to all shower walls to a minimum height of 1800 mm (or the full height if tiling to ceiling)
• Full floor coverage in wet areas
• Extra membrane at corners and junctions — these are the failure points
• Allow full cure time before tiling — typically 24–48 hours depending on product

Skipping waterproofing or doing a half-job causes water ingress into the wall cavity. The damage is invisible until it's extensive — rotting wall frames, mould, and in worst cases structural damage. Fixing it means ripping out the tiles and starting again. The cost of waterproofing a standard bathroom is $100–$200 in materials and a few hours of work. The cost of fixing water damage is thousands.

Step 4 — Grout and adhesive

These are the materials most people forget to plan for properly.

Tile adhesive

Use a flexible polymer-modified adhesive for bathroom tiling — standard cement-based adhesive isn't flexible enough to handle the thermal movement in wet areas. As a guide, allow approximately 4–5 kg per m² for wall tiles using a 10 mm notched trowel, and 5–6 kg per m² for floor tiles (back-buttering required for large format).

Large format tiles (600×600 and above) require back-buttering — applying adhesive to the back of the tile as well as the substrate — to achieve full contact coverage. Skipping back-buttering on large format tiles leaves hollow spots that crack under load.

Grout

Use an epoxy or polymer-modified grout in wet areas — standard cement grout stains, cracks and harbours mould in showers. Mapei, Davco and Bostik all make suitable products widely available at Bunnings and tile suppliers.

As a general guide, allow 1.5–2 kg per m² for standard tiles with 2–3 mm joints. For large format tiles with thin joints (1 mm), allow 0.5–1 kg per m². Your tile supplier can give you a precise figure based on your specific tile size and joint width.

Grout colour

This decision matters more than people realise. Light grout shows every mark in a bathroom — it looks beautiful new and requires regular cleaning to stay that way. Dark grout hides marks but can make a small bathroom feel heavier. Mid-tone grouts that are close to the tile colour (not matching exactly, but harmonising) are the lowest-maintenance choice. Whatever you choose, buy all your grout at once — colour varies between batches.

Step 5 — Choosing the right tile size for your bathroom

The common wisdom that large tiles make small bathrooms look bigger is broadly true — fewer grout lines, less visual busyness. But large format tiles have practical constraints:

• 600×1200 mm slabs — dramatic, popular on The Block. Require a very flat substrate (within 3 mm in any 3 m span), full back-buttering, and an experienced tiler. Not a beginner DIY tile.
• 600×600 mm — the sweet spot for most bathrooms. Large enough to look modern, manageable for a competent DIYer, widely available and competitively priced.
• 300×600 mm and 300×300 mm — versatile, easier to work with on awkward layouts, good for shower floors where fall-to-drain requires flexibility.
• Mosaic and small format — shower floor classic. The small size makes it easier to achieve the fall-to-drain without cutting issues, and the higher grout-to-tile ratio provides better slip resistance.

What not to skimp on

After talking through bathroom renos with people who've done them, the things people most regret cutting corners on are consistently:

• Waterproofing — already covered above. Never skip it.
• Tile quality — cheap tiles from a clearance bin often have size variation that makes grout lines inconsistent. Buy from a reputable supplier with consistent sizing.
• Grout quality — standard cement grout in a shower looks tired within 2 years. Epoxy or polymer-modified grout lasts far longer and stays cleaner.
• Buying enough tiles in one batch — running short and ordering more from a different batch is the most common tiling regret. The colour difference is visible. Order enough upfront.

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