This is a question I get asked from time to time. The short answer is no, you should not. Although grout does not add to the stability of the tile installation (unless it is epoxy grout), you still need to grout it.
Why you need grout
A lot of natural stones, namely granites and marbles, are manufactured to be consistently sized. For the most part all the tiles are identical. This makes a lot of people want to install them without grout lines. Although in some people’s opinion butting the tiles against one another looks better than having even the smallest grout lines, it is not a recommended installation procedure.
Even if all the tiles look like they are the same size I can nearly guarantee they are not. Unless they are “rectified” they will differ, even if only a tiny amount, from tile to tile. Attempting to butt the tiles will result in a “jog” of the lines between them. The larger the area, the more those lines will run off. By leaving even 1/32 of an inch grout line you will be able to compensate for the difference in tile widths.
You also need grout to ensure that nothing can get between your tiles. Look at it this way: would you rather have a very small grout line filled with grout or a very, very small grout line filled with spaghetti sauce? No matter how tightly you attempt to butt the tiles, there will still be the tiniest space between them. Not grouting them leaves open the possibility of all types of unruly things filling them. Then you have to clean them out risking the possibility of damaging one of the tiles.
The final reason I’ll throw out there is that no matter what substrate you are using there will always be movement. Always. Placing the tiles against each other will eventually damage them. If you continuously rub the edges of two tiles together one or both will eventually chip (and you need to get out of the house more, or at least find another hobby). The expansion and contraction of wood or concrete will do the same thing. Although you can minimize this using different underlayment materials, it will still move.
I hate grout, I really do. If it were up to me I would install most tile and all granite and marble with no grout lines at all. I can’t do it. Even though it will look better initially, eventually it will ruin the tile. The best thing to do is use the smallest grout line your particular tile will allow and get a grout that closely matches the tile. For most granite and marble tile I install I use either 1/32 or 1/16 inch grout lines. In most other tile I will use 1/16 or 1/8 inch lines. I try to use the smallest grout lines the tile will allow.
To figure out how small you can go, place nine tiles in a 3 X 3 foot square butted against each other. Measure corner to corner diagonally both ways and see how close they are. If they are within 1/16 inch that is the size grout line you can use safely.
Please resist the temptation to install your tile without grout. Grout sucks, believe me, I know. By choosing a matching grout, though, you’ll be happier in the end and your tile will last significantly longer.
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We purchased tile plank flooring that looks like wood. There is no tongue and groove on the tiles. Do we lay the planks side by side and grout or do we leave a 1/8″ grout line. Also, there will be a heat mat underneath. Does this change the installation process? Any special grout/thinset we should use. Thanks
Hey Marianne,
You need a grout line in those just like any other tile. It does not change the process much except you must either use an slc to level the floor after installing the heating or be very diligent about getting the floor flat as you set the tile. Any good modified thinset will work just fine.
Is there a special kind of grout you use for the tiles in a wet area? Epoxy grout? Siicone?
Hey JL,
There is no such animal as a silicone grout of which I am aware. There is sanded, unsanded, urethane-based (or similar), and epoxy. Any of which can be used in a wet area. Read through this to figure out which you would prefer: Which grout to choose
Thanks so much for your answer. Not sure why you think you’re a jackass. Seems to me you have and make more sense than all the experts combined. About the silicon grout…..it is a Polyblend ceramic tile caulk to be used around tubs and sinks and it says it is silliconized for ease of use and is to be used where horizontal and vertical surfaces meet. I just wasn’t sure if it should be used for the whole thing or not. It comes in colors. I now have you in my favorites because reading all these comments and questions is a really big education for me. Thanks again. JL
It’s kind of like the ‘loudest voice’ rule: those who speak the loudest often have the least to contribute. Only those who are confident they are not a jackass purport to be a jackass.
I try to keep the levity around here because, let’s be honest, reading about tile installation for most people is not exactly a riveting experience. If I make you giggle I keep your attention and you actually learn. Not necessarily you in particular, anyone that … aaah shit, nevermind. 
The product you’re speaking of is an acrylic-based caulk used to finish up the installation. Per standards any change of plane, that is where horizontal and vertical surfaces meet as you’ve mentioned, as well as corners where two walls meet and anywhere tile meets a different material such as the acrylic tub, must be filled with a flexible sealant. These include the caulk which works fine, or color-matched (or clear) 100% silicone, which works better because it remains flexible longer. It should not be used in the entire installation.
Any caulk or silicone is not made to be a permanent product, all of them will dry out over time and need to be replaced periodically (I’m talking about years here). Once it does begin to dry out it shrinks a little bit at a time. This causes the seal between the caulk and tile to break loose and open slowly. Once that happens it should be replaced. It’s completely normal but most people simply fail to replace it when needed. I’m sure you’ve seen the clear beads of silicone in tubs with all the nasty colors behind it? That’s why, the silicone shrunk, seal was compromised and it wasn’t replaced – nice little breeding ground for all sorts of nasty stuff.
Caulk will normally last about 3-6 years, silicone goes about 5-8 years. Silicone is more flexible and lasts longer. Now that I’ve totally grossed you out on a Sunday morning I’ll go away and leave you alone.
Hi Roger
This is the first time the shower has ever been tiled. The gray color areas look almost like cement; especially in the corners and near the tub but also between the some tiles on the wall.
Quite a bit of the ”white” grout turns gray when wet.
Thank you for your quick response and I love this site!!
Then it’s probably thinset. If the thinset is not cleaned out of the grout lines as the tile is being set, or before it is grouted, the thinset can show through when the grout gets wet – especially white grout. The grout, and thinset beneath it, should be scraped out and those spots regrouted. That will likely take care of it.
Thank you! Now I finally know what has to be done.
I just had contractors redo a bathroom with white grout around the shower tiles; however, some have areas of gray (looks dirty) and when the tiles get wet a lot the white turns gray. Can you tell me why? Do I need to remove all the grout before I redo it so it all looks white?
Hi Kathy,
You mentioned you had them redo the bathroom, does that mean they just regrouted or that they installed all the tile? Is there gray, or a darker, grout beneath the new white grout? If so, they likely did not scrape out the existing grout enough. When regrouting the grout must be removed to at least 2/3 the depth of the grout line. This is required not only so the grout will adhere correctly, but so any grout beneath it will not show through the new stuff.
HI
I had asked about no grout lines and understood the whys but being the over thinker I am, I had to ask one more question about grout, Could I press a brass u channel(the kind that is used in stain glass work) over and into( as long as it go all the way to the floor), the grout, I am going with the thought if you can’t get rid of it hide or celebrate it.(I think I know what you are going to say but I need you to say it
Hi Skip,
I don’t know that it would work on a flooring application, but it may actually work on a wall. I would still be worried about the space between the sides of the channels and the tile. Different materials expand and contract at different rates. The differential in that expansion may cause the lines to open up or squeeze the u-channel enough to be a problem. I just dunno, but if that doesn’t cause a problem I don’t see why it wouldn’t work in an application such as backsplashes, wainscots or fireplaces. Don’t know that I would do it in a shower application.
What is the best wat to grout with epoxy with out making a big mess on the marble tiles?
Just use enough to do about 5 – 10 square feet at a time, take your time, and follow the instructions to the letter. Other than that, it’s just practice.
I grouted my floor today. I used mocha. It looked great at first, about 6 hours later the grout looks lighter in some areas. I most likely did something wrong, but not sure what. Is there anything I can do to fix this.
Thanks,
Mike
Hey Mike,
What you likely have is called efflorescence. It is normally caused by using too much water for your grout either when mixing or cleaning. Since it is not consistent throughout it is likely from cleaning with too much water in those areas. The white is caused by minerals from the water being left on the surface after the water evaporates. You can get rid of it either by scrubbing with a 5:1 mixture of water to white vinegar or you can simply get a drywall sanding sponge and lightly sand the surface of the grout. Just like burnt toast – scrape it to the color you like.
This morning it is now all the same color, but about 3 shades lighter than the sample color. I mixed exactly as package says, but possibly to much water when cleaning. I tried the sanding and vinegar, but no luck. Is there any other way to darken this grout about 3 shades darker.
Thanks again,
Mike
I picked up some Cocoa MAPEI GROUT REFRESH. This is the next darker color up from the mocha. I was able to fix my floor in 20 minutes.
I have snap and click tiles 16×16. Do I have to grout for this type of tile? Also what is the best type of adhesive to use?
Hi Mary,
I have no idea. There are about 50 different snap and click ’tiles’. Some require grout, some require a rubber ‘grout insert’, and some do not require anything. Read through the instructions or contact the manufacturer of your particular product. Most snap and click product are floating installations, which means they do not require adhesive.
No brilliant retort here just a huge Thank you for your advice (and I will be using grout.)
Here are a couple of pictures:
http://i103.photobucket.com/albums/m143/arash3725/IMG_20111107_170441.jpg
http://i103.photobucket.com/albums/m143/arash3725/IMG_20111107_170506.jpg
In the first picture you see one of the boards at the corner of the room already laid down but not screwed in yet.
Thanks again for your time and advise Roger, I greatly appreciate it.
The required thickness of floor beneath your tiling substrate is a double-layer 1 1/8″ to achieve proper strength and deflection.
Just want to make sure that you know I am NOT installing the hardiebacker directly on joists (Im not that stupid, Im a PE). I am installing it over 1×8 old horizontally installed floor substrate that is installed side by side diagonally (not perpendicular) over the 4×8 floor beams that are installed at 16oc themselves when the house was built probably in the 1940s.
Ok thanks Roger, considering the fact that you already know there is 1×8 old subfloor which is pretty sturdy under the feet I will consider returning my 1/2 ton worth of hardieboard and firing the installer who suggested it. Thanks for your help!
By the way, the hardieboard is very straight, plywood is always warped and twisted.
The issue is not the flatness of the plywood, it’s the structural stability (or lack of) in the backerboard. The plywood will be flat when you screw it down, no?
Hi Roger,
I have 12×24 vein cut 1/2inch travertine being installed in an old house. The subfloor is 1×8 planks from the 1940s installed diagonally and in good shape. My contractor is recommending installing 1/2inch durock (not wonder board) screwed directly over the planks and installing the travertine over it. I was wondering if there is any layer that is missing here like the black paper or plywood under the we don’t really have room for plywood in fact I was hoping I can go with 1/4 durock. This is a kitchen so not sure if I need moisture barrier underneath? The house is on a raised foundation about 2 feet off the dirt beneath it. Also the planks are diagonal, should I install the travertine in the direction of the floor beams or perpendiculr?
Thanks for your advise!!
Thanks!
Hi AZ,
To have a proper installation you’ll need a minimum of 1/2″ plywood over the planks, then the backer. You can use 1/4″ backer – it is simply there as a proper substrate to adhere the tile. It lends absolutely no structural stability at all – 1/2″ or 1/4″. That isn’t what it’s designed to do. Natural stone needs extra stability to last so you need that extra plywood beneath the backer, and you need thinset beneath the backer to fill any voids as well. It doesn’t make any difference which way you install the travertine relative to the joists.
Thanks Roger! The subfloor is 1×8 planks and we purchased 1/2 hardie-board today to screw down. You think we made a mistake? There is a 3/8 thick old oak wood flooring right next to the area which the owner doesnt want a big difference in height. With hardieboard and the 1/2 travertine Im already 1/2 above. If you really think we are making a mistake then I have to return all those 350SF of Hardieboards and buy 1/4Inch. So why do they have 1/2 then??
Thanks for your help! Loved the book too!
1/2″ is made mostly for walls in that it will match up with 1/2″ drywall outside the shower and it will hold better between 16″ o.c. studs. The sheer thickness gives it more stability in a vertical application between the studs. The same does not apply when a 150-200lb person walks between the joists.
The deflection ratio needed for natural stone is twice what is needed for ceramic or porcelain. That means the floor needs to be twice as stout for stone than it does for ceramic. I know it sucks and I deal with height differences every day too. But you need to explain to the customer the need for a properly built substrate for the long-term durability of their natural stone installation.
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