Diagonal Tile Laying

Preparing the base

The base must be solid, dry, clean and flat. A diagonal layout will not hide an uneven floor. On angled lines every lip between tiles shows even more clearly. Larger dips are levelled with self-levelling compound, cracks and holes are repaired, and finally a primer goes on so the adhesive bonds properly. In bathrooms and showers, waterproofing (often called tanking) belongs under the tiles.

Setting out the lines

This is the most important step. The tiler finds the centre of the room and marks two lines at right angles to each other, both at 45° to the main wall. The tiles are then usually laid out dry first, to see where the cuts will fall at the walls and in the doorway. The aim is to avoid thin slivers at the entrance and in other visible places, and to get even, reasonably large pieces instead.

Fixing the tiles

Adhesive is spread with a notched trowel over a small area at a time, so it can still grip the tile before it starts to skin over. Tiling starts at the centre lines and works outwards. Spacers or a tile levelling system keep the joints even. With larger tiles, adhesive is also spread on the back of each tile so no hollow spots are left underneath.

Cutting the edges

Along the walls you end up with triangles and trapezoid shapes. These are cut with a tile cutter or a wet saw with a diamond blade. Skirting boards usually cover the cuts at the walls, but at doorways, around the bath or at the shower tray the cuts have to be clean.

Grouting and cleaning

Once the adhesive has set, usually after about a day according to the manufacturer, the joints are grouted. A movement gap is left at the walls and in the corners, and this is later filled with a flexible sealant. Finally the floor is washed to remove grout haze, and if needed the grout or natural stone is sealed.

A diagonal works well with medium-sized square tiles. In a narrow hallway or a small bathroom it breaks up the "corridor" effect and the space feels wider. It also suits rooms where the walls are not quite square, which is common in older houses. Parallel joints would give away the uneven walls, while angled joints make it much less noticeable.

It is less suitable for large-format tiles. The cuts are big, there is a lot of waste and the tiles are harder to handle. Rectangular tiles can also be laid diagonally, but it helps to picture the pattern in advance. If the floor continues into the next room, think about whether two different directions meeting at the threshold will look awkward.

• Room shape: every corner, alcove, pipe boxing or door frame means more angled cuts.
• Tile size and material: large formats, hard porcelain and natural stone take longer to cut.
• Condition of the base: if the floor needs levelling, repairs or waterproofing, there is extra work plus drying time.
• Patterns and combinations: alternating colours, inserts or a straight border around the edge all need more careful planning.
• Material use: a diagonal layout produces more offcuts, so you need a bigger allowance than for straight tiling.

In a flat, it is worth checking with the building management or owners' association when noisy work such as cutting tiles or breaking up an old floor is allowed. Simply replacing a floor finish does not usually need any approval. If the tiling is part of a larger renovation, check with your local building authority what applies.

• Starting from a wall: the angle gradually drifts and you end up with ugly thin cuts on the far side of the room.
• Not checking the angle: a tiny error at the start becomes visible after a few rows.
• Too little adhesive under the tile: hollow spots sound drummy later, and the tile can crack under load.
• No movement gaps: tiles pushed tight against the wall can lift or crack as the temperature changes.
• Too few spare tiles: if you run out, a new delivery may be a slightly different shade.

If you have tiled a floor the standard way before and you are patient, you can manage a diagonal layout yourself. Expect it to take longer, with a lot of the time spent cutting.

1. Check the floor is flat with a long straightedge and level out any dips.
2. Clean the base and apply primer following the manufacturer's instructions.
3. Find the centre of the room and mark two lines at right angles, both at 45° to the main wall.
4. Lay the tiles out dry and shift the lines so the cuts at the entrance come out even.
5. Spread adhesive with a notched trowel over small areas at a time.
6. Place the first tile exactly on the lines and check it with a spirit level.
7. Work outwards using spacers, checking the angle and the level as you go.
8. Cut and fix the edge pieces, leaving a movement gap at the walls.
9. Once the adhesive has set, grout the joints and wipe the surface with a damp sponge.
10. Fill the movement gaps at the walls and in the corners with flexible sealant.

• Joints are the same width and run in straight diagonal lines
• The angle of the pattern is the same across the whole room and lines up with the threshold
• Cuts at the entrance and in visible places are even and clean
• There are no lips between tiles and neighbouring edges sit flush
• Tiles do not sound hollow when tapped, which would point to a gap underneath
• Movement gaps at the walls are filled with flexible sealant
• The surface is clean, with no adhesive or grout residue
• You have a few spare tiles left from the same batch