Once you've marked out the two centrelines, you can look at the issue of where the tiles will fall, and how wide the border tiles will be against the walls.

The border tiles - also called 'perimeter tiles' - are the ones that go around the perimeter of the room.

They enclose the field tiles that form the main body of the floor.

What you're trying to avoid is a narrow strip of border tiles, which not only looks less pleasing to the eye, but also accentuates any taper that might occur if the opposing walls are not parallel.

You also need to set out where the tiles will fall in relation to any architectural features in the room, such as columns, recesses or projections.

If you can avoid awkward cuts or small fill-in pieces, the job will be easier to do and the final result will look more professional.

Some installers physically lay out the tiles along the centrelines towards the two adjacent walls.

This is called 'dry laying', and it lets you see exactly how wide the border tiles will be against the walls.

Alternatively, you can mark the tile widths (or multiples of the widths) along the centrelines to see where the last full tile will finish.

Another option is to simply do the sums in your head or on a calculator. Below is an example.

Say the tiles are 500 x 500 mm and the length of the line AC is 3250 mm.

The number of tiles along the line AC is:

      3250 ÷ 500 = 6.5 (in other words, 6 ½) tiles

This means that the width of the last tile will be:

      500 x 0.5 = 250 mm

Moving the starting point

There are times when the last row of tiles might end up being a narrow strip. In these cases, you can move the starting point away from the true centre point so that you get a better result.

For example, let's say that the length of the line CD is 2050.

If you used the true centre point C as your starting point, the number of rows would be as shown below.

      2050 ÷ 500 = 4.1

Therefore, the width of the last tile would be:

      500 x 0.1 = 50 mm

The same will occur on the other side, because CE is the same length.

However, if you move the starting point towards E by 250 mm, you would end up with 4 full tiles plus a border tile cut to 300 mm.

      50 + 250 (distance moved) = 300 mm

This means that the starting point will no longer be C - it will now be X.

Note that since XD is longer than the original line by 250 mm, XE will be shorter by the same amount.

So the number of tiles along XE is 3.6, and the width of the border tile is 300 mm.

Here are the calculations.

      XE = 2050 - 250 = 1800

      Number of tiles along XE: 1800 ÷ 500 = 3.6

      Width of the border tile: 500 x 0.6 = 300 mm

The border tiles on both sides are still the same width, but we've managed to avoid a narrow strip against the walls.

You can prove to yourself that the total length of the tiles across the room are unchanged by doing the following sums.

      Total number of tiles along centreline DE: 4100 ÷ 500 = 8.2 tiles

      Number of tiles either side of C = 4.1 (along CD) + 4.1 (along CE)

                            = 8.2 tiles (made up of 8 full tiles + 2 border tiles cut to 50 mm each)

      Number of tiles either side of X = 4.6 (along XD) + 3.6 (along XE)

                            = 8.2 tiles (made up of 7 full tiles + 2 border tiles cut to 300 mm each)

You can see that the centreline AB is no longer our 'working line', that is, the line that we lay the tiles along. The working line is now FG.

This drawing shows the room with the widths of all border tiles marked.