How Large Should Grout Lines Be?

by Roger

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.

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I’m installing 6×6 tiles to even the floor up under the new bathro vanity (don’t ask why we don’t just use a shim, I guess you have to keep the husband happy. But the tile that we have that matches the best is t the same size as the existing tile (7×7) so the grout lines aren’t going to match up unless I use a larger grout line 1/2 at least. Remember that all of this will be hidden under the vanity so it won’t be seen. I’m only worried the what is seen will still look “ok” it’s the part that is right in front of the kick space on the vanity. So like a 2″ wide strip.

Haha so here’s my question. Is 1/2+ grout going to be a problem under the vanity?



Hi Liz,

No, it won’t be a problem.



I am laying 6×24 inch tile in a L shaped bathroom the small section is 25.25x32in could I lay the tile horizontally which would be one tile across it would leave me with just over 1/2 inch on each side? Would that be too large of a grout line? When the moulding is placed it will actually cover most of the space but I was wondering if a 1/2in grout line would be structurally sound, also what size grout line would you suggest for the rest of the job thankyou



Hi Mark,

A 1/2″ grout line is huge. Since your molding will cover most of it you would be better off ripping some 1/2″ strips down for the sides to both make a consistent grout line with the rest of your floor and to support the molding. I normally use 1/8″ on floors if the tile allows for it.



I am in the process of having 2 bathroom “professionally” remodeled. The tile installer installed new boards around the shower to place the wall tile. However, the final bull nose tile rested on the existing wall. He finished grouting today and I notice that the outside grout went from about a quarter inch thickness at the bottom of the wall to in excess of a half inch as it get to the top. The company reason was my walls are not straight. From a professional stand point what should my expectation be as far as uniformity and how can I hide or disguise the thick grout border. Would you suggest painting the same color as the wall? Thanks



Hi Jerry,

I’m not quite understanding. Is the inconsistent gap between the back of the bullnose tile and the existing drywall? If so then their reasoning is correct. And having a level, flat and plumb tile installation over an unlevel wall will show that. While there are ways to fix that it involves either reshimming the existing wall or not having a level tile installation.

You can paint that the same color as the wall, that will hide it some. A piece of wooden trim will hide it as well, but may look like crap.



I am installing 12×24 porcelain tiles on bathroom floor in a brick pattern. The space is fairly small. The grout is matching so there will not be a great contrast. I only want to use a 1/8 inch grout line. Will this look okay? Should I use sanded grout? Thank you!



Hi Elaine,

It will be fine with 1/8″ grout lines.



The wife has chosen 4″ by 16″ tiles for the new ‘shower only’.
My question is about the choice of notched trowel to use…with rectangular tile how do you choose? Do I base it on the short side so it doesn’t ooze or the long side for coverage? As well, does it make a difference whether they are horizontal or vertical, i.e… Do I base it on the vertical aspect for sufficient strength or am I over thinking this?
Thanks in advance mate…



Hi nthian (?),

long or short, horizontal or vertical, none of it matters. The correct trowel size is the one that gives you proper coverage beneath the entire tile.



Off topic a bit – I love the shower you’re showing on this page! Can you tell me about it? Is that slate? Who’s is the vendor. Any info would be greatly appreciated. Thanks!



Hi Bill,

If you’re speaking of the photo in the upper right-hand corner I have no idea what shower you were looking at. Those photos rotate randomly, it could have been one of about 75 or so. I have done one slate shower, I don’t remember the manufacturer, but I know it was REALLY good slate and ran about $25/square foot. You can read about that here: TileArt Slate Master Bathroom



I am going to tile my kitchen back splash with 3 x 6 glass tiles. When reading your information I noticed that with small tiles you recommend the 1/16 or 1/8 spacers. I believe I read (some place else) that with glass tiles you should not go any smaller then the 1/8. The tile may crack if there is any movement in the wall. I would like to use the 1/16th because the tiles will fit better and look good. What is your opinion? Want to get started soon.




Hi Dawn,

It can be done provided the consistency of the tile allows it.


David. J. Harrison

I am about to waterproof the bathroon floor in my apartment, I wish to use a Beige water proof adhesive/grout all in one, would you recommend this & if so do I need a special type of adhesive as its going onto a waterproof floor paint?



Hi David,

I can give you zero advice until I know exactly what ‘waterproof floor paint’ is. :D



Hi Roger,

I’m tiling wth 12 X 24 tiles on the wall around the bath/shower (already did the floor). I will have an accent strip of glass mosaic about 4 inches wind all around the room and serving as my backsplash on for the vanity.

Couple questions. I am using sanded grout with 1/8 inch lines. When i grout the glass, do I need to protect it somehow first to prevent the grout from scratching it?

Also the glass tile is 1/4 thick, the field tile is 3/8 inch. Should i put extra thinset on on the glass to make it flush with the other tile or is that usually not something people worry about.

Thanks. John



Hi John,

Sanded grout will not normally scratch your glass, it’s more durable than that. Always test first, but I’ve only ever had two glass tiles that scratched with sanded grout – both were over $100 a square foot. Go figure. :D

Extra thinset, ditra, backer, etc. Anything to bring it out flush with the wall tile. Only worry about it if you want your tile to look normal. :D



Hi there. Great info on this thread. I’m getting ready to tile my 11×13 kitchen using 18 inch tiles. I bought a ’78 Florida home and for some reason the cool thing at the time was a small step down into the living spaces (about three inches). The substrate is concrete slab. I want to tile the face of the “step” (the vertical part) from the kitchen to the living room. I was thinking the best thing to do was tile the face of the step and cut the tile so it’s flush with the horizontal part of the slab, then finish tiling the entire horizontal surface. Is this a good idea? Also, the slab is not completely level (1/4 inch in some areas). Do I have to level it out first or can I make up the difference with thin set? Thanks in advance!



Hi Janelle,

You can do that, but it would be best to have a membrane like ditra on the horizontal portion of the step. You can level it out as you instal the ditra. If you do go directly to the step, you can level it out with thinset (in layers), but it may not work as well and 1/4″ is a LOT to make up with thinset.


DIY Oger

Hello there floor elf,

I love your site, it makes an old grouchy Oger feel right at home with you the elf, doing all the work and me the Oger taking all the credit for a job well done.

Well, now that the pleasantries are over, how about you giving el grouchy your take on SpectraLOCK Pro Premium Grout in white. Thanks to you the smart aleck…er….knowledgeable elf, the missus won’t scratch me warts until I get the freaking cave hole…errr bathroom done! :wtf:

So I have liberated a few boxes of Emser Times Square white polished porcelain tiles 12″ x 12.” These bad boys will make any king proud to lay his delicate stockinged feet on.
I want to use that fancy grout of yours with 1/8 or 1/16 grout lines if the tiles measure square and proper.The missus wants white grout to match the tiles. :censored:

As king of my bog, I said a light gray grout of maybe some of that blingy Dazzle in pearl or silver shadow….hey Ogers dream big too baby! What say you?

Is SpectraLOCK Pro Premium Grout in white up to the task of staying white (for all intents and purposes, a bathroom floor)?

Does Dazzle rub off under moderated mopping or bristle brush cleaning?

Oh yes, before I get back to raiding the pastures for sheep, trashing a few villages and cracking a few skulls, what’s the difference between the pro premium and the 2000 industrial grade?

See you around floor elf ;> :evil:



Greetings Ogre,

Concerning the durability of the spectralock it is stout enough to be molded, cured and lobbed over moats and castle walls by a mildly hefty catapult without disintegrating on impact.

I’m unsure if the dazzle component would turn it into shrapnel at landing, but I doubt it. The dazzle components are embedded into cured, inert epoxy and I have not heard that the component weakens the overall structural integrity of your munitions. It would be a spectacular, shiny explosion, though. :D

Your munitions would also manage to remain white, no matter how many castle walls or dragons it smashes through.

The industrial grade is only different in that it would stand up to commercial cleaners the wenches use in industrial settings. For regular castle cave holes with normal cleaning the wenches missus won’t have any issues with regular pro premium.



Hello Roger, currently doing my bathroom using 12 x 12 tiles on the floor and walls with a 1/8 spacer grout joint. I know a joint this size can take either sanded or unsanded grout. If you had your druthers which would you prefer and why. Thanks



Hi Jack,

Sanded, because it doesn’t shrink.


Joe P


I am installing an accent border made if small travertine/stone strips of tile attached by that backing mesh stuff. There is practically no space between the strips unless I curve the mesh to spread out the tiles. How would I grout something like this? I haven’t put it on the wall yet.



Hi Joe,

Some of those mosaics have nearly no space for grout. Just go over it really well with the grout, wipe it down, then go over it again right away. After it cured inspect it for any spots that may have been missed and just fill them in with more grout. It’s pretty tedious, but works well.


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