The size of grout lines for tile is something that comes up on almost every tile installation. The secret no professional will tell you is there is really no set or absolute proper size for your grout lines. There are some guidelines that need to be followed but the actual size is more of a personal choice than it is a set width.

Grout line guidelines

Since grout line widths are generally a personal preference I’ll let you know what mine are. I separate most tiles into three different categories:

• Small format tile – Tiles up to and including 8 X 8 inches square.
• Regular – 12 X 12 up to 16 X 16 inches square.
• Large format tile – 18 X 18 inches and larger.

These are not technically official category names for tile sizes – it’s just what I call them. I’m weird like that.

Small format tile

A lot of smaller format tiles are self-spacing. That means that on either two or four sides of each tile there are what are called “lugs”. Lugged tile have small bumps or protrusions on the sides which are set directly against the tile next to it. Most of these tiles are made specifically for vertical applications, those are shower walls, backsplashes, etc., rather than floors.

The lugs on the tiles allow them to be stacked atop one another and keep the grout lines consistent throughout the installation. For tiles with lugs on only two sides of each tile you must make sure they are all stacked in the same direction, that the lugs are not butted against each other. Normally the lugs will create grout lines that are 1/32 to 1/16 of an inch.

For small format tiles that do not have lugs I will usually use 1/16″ spacers. Depending upon the texture and consistency of the tiles I may use 1/8″ spacers on occasion. For instance 8 inch slate tiles will usually look better with a slightly larger grout line.

If you prefer larger grout lines but have lugged tiles – don’t panic. You can still use spacers with the lugs. To ensure consistency you need to make sure that you either put the spacers between all the lugs or between the spaces the lugs are not. In other words do not put a spacer between the lugs on one tile and between spaces where there are not lugs on another. To figure out the size of your grout lines you also need to add the size of the lugs to the size of the spacer if you use the spacers between them.

Regular format

Regular format tiles are what I install on most of my jobs. More often than not I will use 1/16″ grout lines on vertical surfaces and 1/8″ lines on floors. I just think it looks better and as long as the tile is consistent enough, that’s what I’ll use. I will usually use the smallest grout line the tile will allow.

The best way to figure out how small you can go is to lay out nine tiles in a square and measure from corner to corner in both directions. If they are within 1/16 inch you can go that small with your grout lines. Some tiles such as slate and some quarry tiles will not be consistent enough to use a grout line that small. The largest grout line I will use is 3/16″ unless otherwise specified by the builder or customer.

Large format

Large format tiles are a bit tricky. These, more than either of the other two, are more dependent upon the tile itself. While most people will purchase larger format tiles specifically because they do not want a lot of grout lines, sometimes the tile will not allow it. Although this is rarely a problem, you need to be aware of it and make sure you check the tiles before you try to go with a very small grout line.

The easiest way to check larger format tiles is simply to measure corner to corner in each direction to ensure squareness. As long as they are the same in both directions, they’re square. Then measure several different tiles from different boxes. With a very good tile you should get exactly the same measurement every time. If that’s the case, you can use a 1/16″ grout line and not have any problems.

Large format tiles with 1/16″ or 1/32″ grout lines and a grout that matches the tile color closely looks great! If done correctly it will almost look like a single large slab of tile.

Which do you prefer?

As you can see there is really no absolute answer. If you like smaller grout lines, as long as the tile will allow it, use them. If you prefer larger, use larger. As a general rule do not go larger than 3/16″ although under certain circumstances such as some slates and quarry tiles, 1/4″ is acceptable.

If you choose to use smaller grout lines you must ensure the tile will allow it. If you don’t you may end up with lines that “jog”. That means the lines will not be perfectly straight and will jump over just a bit with every tile due to inconsistencies in tile sizes.

If you prefer larger grout lines you need to take into consideration the “grid effect”. If you do not use a grout that somewhat matches the tile color you may end up with an installation that looks more like a grid made of grout than tile with a grout accent. The smaller the tile, the more pronounced this effect may become.

No matter which you choose, you must make sure you use the correct type of grout. If your grout is chosen and installed correctly your good tile installation can turn into a great one. Make sure you consider your grout as much as you consider your tile. It can make or break your whole look.