Caulk or Grout in Corners?

by Roger

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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Ramon

O.K. Roger…here we go again…this time my customer chose real slate 12″ x 12″ for the walls of the shower. I convinced them to use faux slate porcelain 2″ x 2″ mosaics for the floor only! I am using Kerdi board this job and Schleuter shower pan and drain..other than the sheer weight of each tile any pointers as to how to keep them on the wall…no slipping, proper mortar etc. Also can the edges be sanded down to a bullnose edge or is Sleuter strip in order…noticed that thickness is NOT uniform…Hate Slate!

Reply

Roger

Hi Ramon,

I hate slate too. Just support each row with the row below it. Regular unmodified thinset will be fine. Yes, it can be sanded down for bullnose, but depending on the slate it may begin to ‘cleave’, or separate along the layers, when you do it. An edge trim is normally a better choice.

Reply

Sue

I noticed that most tile caulk comes as sanded or un-sanded. Do the same rules apply as sanded and un-sanded grout (1/8″ gaps)? I’m trying to figure out what to use for my shower corners and floor changes of plane where they are butted up against each other. There are more colors available with the sanded caulk but if the 1/8″ gap rule applies then I guess we’re stuck with a smaller color selection.

Thanks for all of your help.

Reply

Roger

Hi Sue,

You can use either, it’s sticky. As a general rule yes, the same rules apply. But you can use sanded caulk in butted corners. (WHY are they butted?!?)

Reply

Sue

We went ahead and butted the tile because your article above stated:

“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.”

Now you have me nervous. Is there an issue?

Reply

Roger

Hi Sue,

It depends on how much your walls move. No way to tell unless a problem arises. It may be just fine.

Reply

jeff

Just wanna say thank you roger . and ask if you have any tips on minimizing lipage on a uneven wall ? never noticed it till now , first ever tile job or ida corrected this before the backerboard went on live and learn but to far to back up now . Redgaurded and all so just wondering if theres a way to minimize the lipping ? thank you roger

Reply

Roger

Hi Jeff,

I would use a larger trowel to give you the ability to adjust the tile in or out as needed.

Reply

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