One of the most asked questions by do-it-yourselfer’s is whether they should use caulk or grout in the corners. Industry standards state that a flexible material be used at all changes of plane. But! – if you ask a hundred different professionals you will more than likely receive fifty of each answer.  While there are pros and cons of each, I am in the camp that uses caulk. That being the case, I will discuss using grout first. I’m backwards like that.

Using Grout at Changes of Plane

While the phrase “changes of plane” may sound a bit uppity or technical – it’s not. It simply describes the corner or edge of any surface that changes direction such as a corner, a wall to a floor, or a wall to the tub edge. Many professionals simply grout that corner as they do any other space between the tiles. There are a couple of things that must be taken into consideration before choosing this method.

  1. Your walls and the framing of your shower must be absolutely rock solid. I do mean absolutely. Grout is a cement-based product and as such is not meant to flex. If your wall moves your grout will eventually crack – it’s that simple.
  2. The space between the tiles at the change of plane must be large enough (for sanded grout) or small enough (for non-sanded grout) to be able to support the grout. That simply means that if you are using sanded grout you cannot butt the tiles against each other at the corner and expect to be able to force grout into it. It will not stay if the grout has no grout line to hold onto – if it is simply attempting to grab onto the face of the tiles at a 90 degree angle. There must be a grout line at the changes of plane.
  3. You must decide you are going to use grout at the changes of plane before you install the tile. You can then make sure to leave a line for the grout as well as adding additional support for any spots that may move even the tiniest bit (which it should not do anyway).

If you have taken the above points into consideration and still decide to use grout in the corners – go ahead. The big advantages of using grout here is that it will match all the grout lines and it will never have to be replaced. So although extra care must be taken to properly use grout at your plane changes, the advantages for some people are worth the extra time.

Using Caulk at Changes of Plane

There are several advantages to using caulk in corners and any other area where there may be a plane change or where tile meets another material such as your bathtub or sink.

  1. Unlike grout you are able to use caulk in a corner where tiles are butted against each other. It will stick to the face of the tile rather than needing a space between the tiles to grab.
  2. Caulk is flexible. If there is any movement the caulk is flexible enough to move with it and remain in place. It will not crack out or fall off.
  3. Caulk is waterproof – grout is not. Water will collect in corners such as where your tile meets the tub more than it will on the face of the tile.
  4. If your caulk does crack out or need to be replaced it is easily done.

The only two disadvantages to using caulk instead of grout are that you need to periodically remove and replace the caulk and, depending on your choice of grout, you may not be able to find a caulk that matches exactly. The first reason I consider to simply be regular maintenance and the latter is less of a problem since most major grout manufacturers sell matching caulk.

When to Use Grout

The only time I will use grout for a plane change is when I am using epoxy grout. Epoxy grout is bulletproof! OK, maybe it’s not bulletproof but you can hit it with a hammer a couple of times before it chips. (Don’t do that.) If you are using epoxy go ahead and grout the corners and changes of plane as well. Although it is not flexible it will grab the tile well enough to prevent it from splitting or cracking out. Precautions must still be taken but the Epoxy is strong enough to withstand normal structural movement.

How to Decide

Given the above parameters I believe caulk to always be the best choice. What you must understand about tile installation is no matter where you are installing the tile, it is always a structure that moves, no matter how minutely. Concrete moves, (the ground beneath it) that’s why it has expansion joints – to control where the movement goes. Most shower installations are over a wood structure of some sort. Whether you have drywall, backerboard, or a membrane, if you go far enough behind the tile, you’ll find wood. Wood moves, it’s just a fact of life. Humidity, weather, even the structure’s foundation all affect how much it moves. By taking proper precautions you can minimize the movement, but it’s still gonna move. Taking structural movement into consideration caulk is, for me, the logical choice.

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  • John

    Hi Roger, I’m installing my first tile shower over an acrylic shower pan (Sterling) using 4×12 white tile. I have two questions 1) I had to cut out the durock around the flange clips in order to lay flat just above the flange. Will I be OK if I fill with thinset/mesh tape then run a strip of fabric/aquadefense down to the flange? I am using the Aquadefense to waterproof the entire shower. The tile will drop down to within 1/8 inch of the pan. 2) Regarding the change of plans, can I still leave a gap of 1/8 inch at the corner tiles and fill with 100% white silicone (grout will be white) or do you recommend a butt joint? Under will be thinset/mesh tape (might fabric these also). Thank you. Great website by the way.

    • Roger

      Hi John,

      1. Yes, the mesh tape with AD is fine.
      2. Always leave a joint for silicone.

      • John


        Thanks for the above comment. I’m slowly plugging away on installing the tile and have decided to add a niche. What do you use for the bottom of the niche? Would like some sort of shelf. Saw some large cultured marble floor tiles and thresholds at HD and Lowes that would need to be cut down. Doesn’t have a finished edge though. Have you ever used those? Either that or I can visit some tile/granite stores for a remnant. Also, do you have a grout preference? Was leaning towards the Mapei Flexcolor CQ or Fusion Pro. Trying to stay away from epoxy grout. Tiles are white 4×12 with 1/16″ grout joint. Thank you.

        • Roger

          Hi John,

          I have used nearly everything for shelves. The thresholds work well, you can ‘polish’ the edge of the threshold by coating it with an enhancing sealer, or sanding it (orbital or vibrating sander) with progressive grits up to about 2000 or so, the shine will match the finished surface.
          Both grouts you’ve mentioned work well. I am currently using Laticrete permacolor select as my goto grout – it’s good stuff too.

  • Will

    I was planning on grouting the corners, so the tiles are not butted together. Then afterward, caulking over the corner. Is that ok? Or should I just caulk? The gaps are 3/16”. I want to use caulk, but thought you had to grout underneath, oops.

    • Roger

      Hi Will,

      Placing caulk over grout in the corners will just lead to cracked grout in the corners that can not fall out – but it’ll still be cracked. With gaps that large what you can do it install a bead of silicone against one side about 1/8″ thick (leaving the rest of the gap open), then once cured grout between the tile and silicone. This will allow the corner to expand and contract without cracking the grout.

  • Bill

    Our installer did not seal where tub meets tile/grout. So, even though the shower has hardly been used and it has been over a year since last use, we have suddenly developed pink grout! We have tried cleaning with baking soda, hydrogen peroxide, bubbling bathroom cleaner and Clorox and it has not done the trick. Question: can we put silicone caulk over these areas to cover pink without causing further issues? We realize we will probably have to remove, clean & recaulk every year. But is it okay to do this? Any suggestions?

    • Roger

      Hi Bill,

      It is not your grout turning pink. It is likely Serratia marcescens, which is a type of water-borne bacteria. It is commonly referred to as ‘pink mold’. If you google pink mold you’ll find several ways to get rid of it. I would not silicone over it until you get rid of it, that’ll just cause it to flourish.

  • Whitney

    I am using the permacolor grout for my shower. I am going to use either latasil or laticrete premium acrylic caulk for the changes of plane. The laticrete supplier in my area said the caulk is what they sell. I would think the latasil would be the better option but would have to order online. Thoughts on which option is better? Also do I caulk/silicone changes of plane before grouting or vice versa? Finally, I watched the video by laticrete on how to install the latasil and they were using some type of “gasket” in the changes of plane prior to the latasil. They didn’t mention what it was. If that is something I need to use… Then what is it?

    Thank you for all of your help. I bought you liquid waterproofing ebook and it was a great help.

    • Roger

      Hi Whitney,

      Latasil will work better, it’s silicone. Regular acrylic caulk will lose it’s elasticity much faster than silicone will, which means it needs to be replaced sooner. Either works, but silicone works better. What they put in there was backer rod. It’s simply cylindrical foam used to fill empty space before caulking. It’s not a gasket, it’s just so you don’t have to stuff so much caulk in there, it just takes up space.

  • Jaque Christo

    Thank you for the post on using caulk or grout in corners. I like the idea to not have to worry about maintenance with grout until it starts cracking. However, I wonder how much it costs to fix cracked grout as you will need to repair it quickly to avoid water seeping through the cracks.

    • Roger

      Hi Jaque,

      It doesn’t matter if it cracks or not, neither grout nor silicone in the corner has anything to do with your waterproofing or preventing water from getting behind your tile – that WILL happen anyway. That’s why you need to have everything waterproofed correctly before any tile is installed.

  • Wayne Spence

    Yeah… The Elf rules.

  • Ranada Hawkins

    Recently I was fortunate enough to have my dream bathroom become a reality.. We hired a licensed contractor do the work. It’s a bathtub/shower combo with porcelain tiles measuring 3×9 in size. Tiles start at the base of the bathtub & go up to the ceiling. After, cleaning the shower I noticed a Slight discoloration on a few areas on the grout. The discoloration is more noticeable on the very bottom row of tile l, where the tile meets the top of the tub & The bottom corner, but also, appearing along the very bottom row of tile where it meets the tub… The grout is a very light gray & the discoloration appears to be a reddish orange in color.. I just cleaned my shower and I do not have any soaps or shampoos that are that color… I am sick to my stomach about this, as we recently had it done in June of this year.. Do you have any suggestions that I may be able to pass along to the contractor to correct this if an issue?? Thank you, Ranada

    • Ranada Hawkins

      Picture listed

    • Roger

      Hi Ranada,

      First: Don’t panic. :D Everything I’m about to tell you is fixable easily.

      The orange discoloration is mold. It’s actually likely Serratia marcescens, which is a bacteria. It is cause by permanently damp conditions (like a shower), especially at the bottom of the tile wall, which is where the water drains to. It can also be caused by hard water deposits. More likely, however, the biggest issue is that the water behind the tile (completely normal) drains to the bottom of the wall and has no way to escape into the tub.

      Here’s how to fix it: Locations of weep holes in showers