How to tile a bathroom floor

Video by Tommy's Trade Secrets. This walk-through is based on the video "Tommy's Trade Secrets - How To Tile A Floor" from the Tommy's Trade Secrets channel. They run through the full process from preparing the subfloor to grouting the finished job. The section on using a notched trowel to get consistent adhesive coverage is particularly handy if you have not tiled before.

1. Prepare the subfloor

Tiles need a solid, flat, dry base. On a timber floor, the boards should be screwed down firmly — any flex will crack the grout and eventually the tiles themselves. Lay 6 mm or 12 mm exterior-grade plywood over the boards, staggering the joints and screwing at 200 mm intervals around the edges and 300 mm across the centre. This stiffens the floor and gives the adhesive something reliable to bond to.

On a concrete floor, check for any high spots with a long straightedge and grind them down, or fill low spots with floor-levelling compound. Damp is the enemy here — if the concrete shows any sign of moisture, treat it with a waterproofing primer before you start. It is an extra step, but skipping it and having tiles lift six months later is considerably more annoying.

2. Find the centre and set out the tiles dry

Measure the room and snap a chalk line down the centre lengthways and another across the width. Where the two lines cross is your starting point. This is not just a theoretical exercise — it is what stops you ending up with a 20 mm sliver of tile next to the bath on one side and a full tile on the other.

Lay a row of tiles out dry from the centre toward the doorway, using tile spacers to represent the grout joints. The aim is to end up with a cut tile at the threshold that is at least half a tile wide. If it looks like it will be less, shift your starting point by half a tile. It only takes a few minutes and saves a lot of cutting. To be fair, most rooms are not perfectly square either, so check both diagonal measurements before you commit to anything.

3. Mix the adhesive and apply it to the floor

Use a flexible floor tile adhesive — a standard wall tile adhesive is not suitable for floors as it is not strong enough to cope with foot traffic and subfloor movement. Mix the adhesive to the consistency of thick peanut butter. It should hold a peak without slumping. Too wet and the tiles will slide; too stiff and it will not key properly to the tile back.

Spread adhesive over an area of roughly 1 m² at a time using the flat side of a notched trowel, then comb it through with the notched side to leave even ridges. The notch size depends on your tile — a 6 mm notch suits most standard bathroom tiles up to about 300 × 300 mm. Larger format tiles (600 mm and above) need a 10 mm notch or you will not get enough coverage on the back. Trowel the adhesive in one direction only — this makes it easier to spot any air pockets when you press the tile down.

4. Lay the tiles from the centre outward

Place your first tile on the centre point, pressing down with a slight twisting motion to bed it into the adhesive. Lift it back up and check the coverage — you want at least 80% of the tile back covered with adhesive, and all four corners in contact. If you are seeing bare patches, back-butter the tile (spread a thin layer on the tile itself) as well as the floor.

Work outward from the centre in a pyramid pattern, dropping tile spacers at each corner as you go. Check with a spirit level every few tiles. On a bathroom floor, a very slight fall toward the drain is desirable, but anything more than a couple of millimetres across a 300 mm tile is noticeable underfoot. Use a rubber mallet and a piece of flat timber to tap any tiles that are riding high. Do not walk on freshly laid tiles — leave them overnight before doing the cut pieces around the edges.

5. Cut the edge tiles and fit them

Measure each cut tile individually rather than assuming the room is square — it almost certainly is not. Mark the cut line with a pencil and tile scribe, then cut with either a manual tile scorer (fine for plain ceramic) or a wet tile saw (better for porcelain or anything larger than 300 mm). Porcelain is tough and will snap unpredictably with a manual cutter, so a wet saw is worth hiring for a full bathroom floor.

For awkward cuts around toilet pedestals, soil pipes, and bath feet, make a card template first. Cut the card to shape, test it for fit, then transfer the shape to the tile. An angle grinder with a diamond blade will cut curves, though a tile saw with a curved cut is cleaner. Mind you, for a back corner nobody will ever see, done is better than perfect — just make sure the grout joint is consistent.

6. Grout the tiles and silicone the edges

Leave the adhesive to cure for at least 24 hours before grouting — longer in cold or damp weather. Remove all tile spacers, then mix the grout to a smooth, lump-free paste. Work it into the joints with a rubber grout float held at 45° to the tiles, pushing firmly in two directions to fill the joints completely. Do not spread too much at once — about 1 m² at a time is manageable before it starts to skin over.

Once the grout has stiffened slightly (around 20–30 minutes), wipe the tiles clean with a damp sponge in a circular motion, rinsing the sponge frequently. A dry cloth polishes off the haze once it has fully dried. Finish by running a bead of sanitary silicone sealant along any internal corners and against the bath or shower tray — these joints will move with the building and grout alone will crack here within months. Smooth the silicone with a wetted finger or a sealant tool, then leave it to cure for 24 hours before using the bathroom.

When to call a handyman

Give Richard a call if the subfloor is springy and you are not sure whether it needs strengthening first, if the bathroom is small with a lot of awkward cuts around a toilet, pedestal basin, and shower tray all in one space, or if you want large-format porcelain tiles that need a wet saw and a bit of experience to cut cleanly. Getting the setting-out wrong on a bathroom floor is an expensive mistake, so it is sometimes worth having a professional do the first course and leaving the straightforward field tiles for a confident DIYer.