How to plan floor tiles

Your first step in laying a new tiled floor

By making sure you’ve got everything you need to begin your floor tiling project, you’ll be able to get it right on your first attempt. Set aside the time to plan properly and you’ll avoid making mistakes, and you won’t waste time or materials. This guide’s here to make sure you don’t miss a step and are properly prepped to crack on with tiling your floor.

how to plan floor tiles

You will need:

How to prepare the existing floor

Firstly, you’ll need to prepare the existing floor.


Clean with detergent mixed with water and if the floor is uneven, level it. Make sure concrete is cured, dust free, solid and primed with an acrylic primer diluted as per the manufacturer's instructions. Then lay tiles directly on the floor.


Timber must be strengthened with thick exterior grade plywood (we recommend 12-15millimetres (mm) fixed with countersunk 25mm wood screws with 4mm gauge at 300mm intervals. Ideally the screws should be 2.5 times the depth of plywood. Make sure you do not go through the floorboards and penetrate any pipes underneath. Joints of plywood should not run parallel to joints on the floorboards.


New tiles can be laid over old vinyl tiles after coating the old tiles with a suitable tile on tile primer.

planning floor tiles

How to calculate tile quantities

Tiles are sold in packs and the size and number of tiles they contain will determine the area of floor they will cover. When you calculate the area of your floor, remember to include the dimensions of any alcove or bay. Round up the total to the nearest whole number to establish the number of packs of tiles you need. Always buy 10% more tiles than you need to allow for cuts and breakages. 

Tiles are often given batch numbers. If this is the case you should always try to purchase tiles from the same batch as a variation in colour or finish can occur- making this another reason to buy plenty of tiles at the beginning of your project.

The first tile, the ‘key’ tile, determines the position of all the others, so it is very important that this tile is in the right place. Because rooms don’t tend to be completely square, and the walls may not be straight, you cannot start by laying tiles right up against one wall and working your way out from there - as you would end up with something unsymmetrical.

The best way to ensure you have a symmetrical design is to start from the centre of the room and work out to the walls in each direction.

Top tip - Awkwardly shaped rooms

If the dimensions of your room are irregular, the chalk lines will need to be snapped from a different place - the first line centred on a strong focal point such as a fireplace or patio doors. The room will still be divided into sections but they will be different from one another.

how to plan floor tiles

Step 1

Measure one wall, calculate its midpoint and mark this on the floor. Repeat with the opposite wall. With a helper, stretch a chalk line between the two marks and snap a line across the floor. Calculate and mark the mid-point of this line. Tie about 1m of string to a pencil, and while your helper holds the end of the string firmly on the mid-point of the line, pull it taught and scribe an arc on the line either side.

plan floor tiles

Step 2

Now get your helper to hold the end of the string on the point that one arc intersects the line, and with the string pulled taught draw arcs at a roughly 45 degree angle either side of the centre line. When you repeat this from the other side, the arcs should intersect.

plan floor tiles

Step 3

Stretch a chalk line between these intersecting arcs and snap a line across the floor.

help planning floor tiles

Step 4

You now have two lines intersecting at a perfect right angle in the centre of the room.

Now that the centre of the room has been found, the next stage is to position the key tile

floor tiles how to plan

Step 1

Start at one of the centre lines, lay out (dry lay) a row of tiles from the line to the wall. When you reach the wall, make sure that you’re not left with a narrow gap - a thin strip of tile at the skirting board will look very odd and may not stick very well. If necessary, move the line away from this wall the width of half a tile to create a larger gap.

how to plan floor tiles

Step 2

Repeat laying out tiles from this centre line in the opposite direction and then in both of the other directions.

how to plan floor tiles

Step 3

Adjust the key tile position as shown, until there is an equal gap of about half a tile at all the edges of the room. Don’t forget to add a gap between the tiles with a tile spacer.