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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Tony

Roger,
I am a GC from MA and have an issue with a tile installation 5 years ago that we are now dealing with. The job was to remove a fiberglass tub, existing floor tile, install an Americast Tub with a new porcelain wall tile surround with antique white grout. We shimmed out the studs and installed hardibacker over flange. We tiled 3/16″ from tub base and then installer grouted all areas. We got a call a month after completion that paint outside of tub on lower wall was flaking and water was getting onto floor. At the time we thought it was a shower curtain issue and owner bought a sliding shower door and we never heard from them again until this summer 4.5 years later. We were told that the tub was still leaking but they didn’t want to be a pain to us. Great people but hard for us to fix something when we don’t know. We should have followed up after shower door company installed looking back at it. Anyways, we used a hose from outside to give it a leak test and both the shower door leaks as well as the corner tile grout 18″ up on mixing valve side. Our original solution was to remove all grout on tub/tile and vertical inside corners and use latticrete silicone color match but owner does not like the “shininess” of it. My next solution is to remove those same areas and use SpectraLock in those same spots. After reading your site, I will use weep holes 1″ behind sliding shower doors and make sure glass door guy removes silicone from inside track and only have it on exterior. If this does not work, we can re-grout all with spectralock as another option or just simply start over and waterproof hardibacker like we do now on all jobs (we started that about 3.5 years ago on these applications and we almost always use Spectralock unless the owners refuse to pay the extra or want some different color/look). Any advice/thoughts on our plan? Thanks

Reply

Roger

Hi Tony,

It sounds like that would be fine, but the silicone would be a much better option due to differential movement on the walls. Have you asked about sanded caulk? It isn’t shiny, she may go for that. You may also want to pull the screws out of the frame and squirt silicone into the penetrations and re-install them.

Reply

Tony

Thank you for the quick reply. BTW, love this site! The tile installer actually used sanded caulk after grout at tub/tile intersection but not on vertical wall intersection. Now, I am not sure he waited for grout to dry properly and/or if that is kosher to do anyways (caulk over permagrout). If it is ok, can I use sanded caulk over vertical corner grout now before I go through with grinding out those corners? The tub/wall intersection is already free of grout/caulk now. For the record, I am not excited about sanded caulk as I am not sure it will pass the leak test like spectralock or silicone but would love to hear your input.

Reply

Roger

It is not there to prevent leaking of any sort. Your shower should be absolutely waterproof before tile is put on the wall. The silicone or caulk is there for purely aesthetic reasons. The reason silicone is better is because it won’t dry out and lose elasticity as quickly as acrylic caulk. You need to remove all the grout from the changes of plane before you caulk it. Caulk or silicone over grout is useless, the grout will still crack and break the bond of the sealant. It should be only silicone or caulk in all those areas, no grout at all.

Reply

Denise Tomion

Hi Roger,
My sanded grout was cracking where the different planes intersect. I have taken MOST of the grout out from those spaces, but I cannot seem to get every little bit out. Can I still put a sanded caulk on those corners/edges?
Thank you,
Denise

Reply

Roger

Hi Denise,

Yes, you can.

Reply

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