Grout Calculator for Dubai and the UAE

Grout fills the joints, so the amount depends entirely on how much joint there is.

A square metre of 600 by 600 tiles has just under three and a half metres of joint in it. The same square metre in 100 by 100 mosaic has about twenty metres of joint.

That is nearly six times as much grout for exactly the same floor area.

Joint width multiplies it again, and so does tile thickness, because a thicker tile means a deeper joint to fill.

This is why a coverage number printed on a bag is only ever a rough guide. It assumes one tile size, one joint width and one thickness, and your job probably matches none of them.

There are two families of grout and they are not close substitutes.

Cement grout is the normal choice. It is cheap, easy to work with, comes in many colours and is straightforward to clean off the tiles.

Its weakness is that it is porous. Water soaks in, and with the water goes dirt, soap and anything else. Over time it darkens, stains and in wet areas grows mould.

Epoxy grout is not porous at all. It resists water, staining and chemicals almost completely, which makes it the right answer for showers, kitchen splashbacks and commercial floors.

The trade off is that it costs several times as much, it is much harder to work with, and it sets fast. Once it is on the tile face and cured, getting it off is a serious job.

So epoxy is worth it where water and staining are constant, and cement is fine everywhere else.

Look at any older bathroom in the UAE and the tiles are usually fine. It is the grout that looks bad.

There are two reasons. It is the softest, most absorbent material in the assembly, and it is at the surface where everything lands on it.

In a shower, water carries soap and body oils into the pores of cement grout. Once it is in, warmth and moisture do the rest, and that is where the black lines come from.

In a kitchen it is grease and food. On a floor it is dirt walked in from outside, which in this country means fine dust.

Sealing helps. A grout sealer fills the pores so liquids sit on top instead of soaking in, and it needs redoing every so often rather than once forever.

The other half is ventilation. A bathroom that dries out between uses does not grow mould in the joints. One that stays damp does, and no amount of cleaning changes that while the fan is inadequate.

This is the most common mistake in tiling and it causes real damage.

The grouting stage is where a good tiling job can still be spoiled, and it happens quickly.

Mix small batches. Grout starts going off as soon as it is mixed, and in this heat that is faster than the bag suggests.

Fill the joints properly by working the float diagonally across them. Wiping along a joint drags grout out rather than pushing it in.

Clean off at the right moment. Too early and you pull grout out of the joints. Too late and the haze on the tile face has hardened and needs chemicals to remove.

Use a barely damp sponge and rinse it constantly. A wet sponge washes cement out of the joint and leaves it weak and patchy in colour.

And let it cure before it gets wet. A shower used the next day has grout that never reached full strength, and it will fail early.