Tile FAQ’s

The list below contains some of the most commonly asked questions I get about tile and installation methods. For each one I have included a (very) short answer.  I already have, or will have in the future, a post about every one of these. If that post already exists there will be a link at the end of the answer.

I will continue to add to this page as the questions come up. If you have a question just leave a comment at the bottom and I’ll include it on this page.

Just click on the question to view the answer.


What type of grout should I use for my tile?

It depends on the tile and the size of the grout lines. Read this: Using the correct type of grout

How large should my grout lines be?

It depends on the tile size and the look you want. Read this: How large should grout lines be?

Can I fill my cracking grout with more grout?

Maybe. Read this article for a more complete answer: Filling grout lines with more grout

Are there any “magic” products available to remove stains from your grout and tile?

No there are not. One of the closest things to magic that you can buy is oxygen bleach. It is not bleach! It's a slight misnomer. This is the main ingredient in products like oxyclean. It works very, very well to clean grout. More information: How to clean grout

Does grout help stabilize tile, hold them in place, or make them stick better?

No it does not. (Epoxy grout is different) Read this: Does grout stabilize tile?

Are tile, stone or grout waterproof?

No they are not. Read this: Is tile waterproof?

Can I install my tile without grout lines?

No, you should not. Read this: Tile with no grout


Can I install floor tiles on my shower walls?

Yes you can. Read this: Floor tiles on a wall


Will sealing your tile and grout make it waterproof?

No! It absolutely will not.

Should I seal (or re-seal) my tile and grout?

If you would like it to be easier to clean then yes, you should.

Setting Materials

What should I use to set my tile?

It depends on where you are installing the tile. Read this: Proper setting materials for tile

Are mastic and pre-mixed “mortar” acceptable to install tile on a floor or in a shower?

No they are not. Read this: Proper setting materials for tile


Does my floor have to be level before I install tile?

No it does not. Read this: Does my floor have to be level for tile?

Do I need a waterproof membrane for my shower walls?

Yes, a membrane of some sort is required. Read the article for the different types. Read this: Preparing a shower wall for tile

Can I simply stick tile to the drywall in my shower or the plywood on my floor?

You can but it won’t last – so no. Read this: Preparing a shower wall for tile or this: Installing backerboard for floor tile


Should I use grout or caulk in the corners of my shower?

Technically? Caulk. Realistically? It depends. Read this: Caulk or grout in corners?

If you have any suggestions or questions please feel free to leave a comment.


Regarding shower walls: I have installed Hardiebacker with no membrane behind so I intend to apply Redgard. I will be tiling with 24″ x 12″ tiles and I am thinking that I should screw a level board to the wall above the tub lip to facilitate getting the first course of tile level etc. Is it ok to do that over the Redgard? When the board gets unscrewed, would I seal the screw holes with silicone or paint more Redgard there?

I am also wondering about the bottom of tile at the tub deck. Is a bead of silicone here sufficient or should I try to get a seal between the Redgard and the deck in addition to that? I was thinking of Redgard over fiberglass tape or maybe a strip of Ice and Water Shield.



Can you use liquid waterproofing and a membrane in a shower? or is it overkill? Would it cause any issues? Thanks for the ebook



Hi Wayne,

No, you want one or the other, never both. It can cause trapped moisture between the two which will subsequently begin to grow mold. It’s lovingly referred to as a ‘mold sandwich’. :D



How can I cut a clean radius in 12×24 porcelein tile to accommodate a 22″ diameter grill. I need the cut to be neat and clean…not sure I can do that with my 4-1/2″ grinder with diamond blade…even if I go really slow and carefully…

Thank you



Hi Bob,

That’s how to do it. Make your clean cut first, with just the edge of the blade only through the glaze of the tile (that’s what chips), all the way around. Then make the cut removing the tile about 1/8″ inside of that cut, then go back and remove the rest of the tile up to the line.


Jesse Steiner

I bought your topical membrane e-book. Great read. I noticed you have to wait 3 days after deck mud is installed to place a liquid topical membrane. My question is can a kerdi membrane be installed the following day after the deck mud has been placed instead of using a liquid membrane?

Thanks for any help



Hi Jesse,

Yes it can be installed the next day.



I removed vinyl (linoleum?) tiles and have adhesive residue on the 5/8 plywood. I can’t get the adhesive up, and now I see that I could have just left the vinyl in place and tiled over it–I’m using Ditra-xl.
Since I can’t get the adhesive up, can I just buy some cheap vinyl tiles and install them, then use ditra on top of them? That seems easier than putting down cement board and then ditra. Thanks, Barbara



Hi Barbara,

It would be easier to just put down a layer of 3/8″ or 1/2″ plywood, then the ditra over that. It doesn’t need to be cement board.


Teresa Aysan

Does this book include the Topical Waterproofing method for shower walls and floor? (I’m asking because the book is called “Traditional”)

How to Build a Traditional Shower for Tile



Hi Teresa,

No, it does not. You need the one titled “Topical Waterproofing for shower floors and walls”. :)



I want to tile over existing Linoleum that is glued to the subfloor, extremely well. Are there going to be any issues if I put a bed of thinset down and then screw hardie board, then thinset and tile?


Bonnie darrah

If you are caulking the line between the granite and tile, should the grout (dark color) be applied prior to cauliking?



Hi Roger,
Can I use a rolled/troweled waterproofing such as Redguard or Laticrete with a Kerdi drain?



John D'Amico

I have a living room that is currently about 4/5 ceramic tile and 1/5 carpet (carpeted area starts in a corner, tile is on the two sides). We want to put laminate wood flooring over all areas. Question: How to raise up the carpeted area level with the surrounding tile prior to laying laminate? Much obliged.



Looking for a suggestion here. A few years ago I tiled my kitchen and dining room using many tips and trick on this site. It has been great as the radiant floor heating is beautifully toasty with tile. Even did it on a 45° bias! Well, fast forward to now and I’ve come across an issue.

I took down a wall to open up the kitchen. I have enough extra tile for most of that however I don’t think I have enough for all. I have 12 pieces and best case I need 15. Four extra pieces are needed where the toe kick of the new peninsula is like 1.5″ back.

Would you suggest any of these or something else?
A- Continued scouring of the internet for extra tile that matches? River stone brown tile.
B- Installing a threshold of sorts where the wall was?
C- Find the closest match to the tile I can and install those under the toe kick.
D-Extra thick toe kick under new peninsula?
E-Tear all of that glorious tile up and redo the floor?

Help requested.





Hi Roger – I bought your books and they have been a HUGE help. I am installing a Schluter shower. I water tested it and it passed. However while tiling the base – I think I might have nicked the kerdi with the edge of the trowel when dumping down mortar. I cleaned the mortar off and didn’t see anything….I hope. I finished tiling the base. Today, I’m concerned. Should I do another water test to confirm?



I am looking for input on our unique situation. Our master bath is an addition and about eight years ago my husband laid the tile in the shower floor and put redgard on the walls over the concrete board (shower pan etc all done properly). Flash forward after raising babies and he just recently installed some travertine on the walls. It looked beautiful! BUT, it became apparent that some, not all, of the tiles did not adhere to the redgard. The modified thinset was adhered to the tile just fine, but literally nothing on the walls. They just popped off – not on their own but with minimal prying. I have looked online about any possible degradation to the regard due to waiting so long but have not found anything. Does anyone have thoughts? At this point I am wanting to use a multipurpose adhesive to stick those tiles back up and then grout the sucker! Seeking wise counsel…………..



Hi Becky,

The redgard likely have dust or debris on it and in the pores of it from sitting so long. You need to apply another coat of redgard over those areas, let it cure, then install the tile with modified thinset. It will bond just fine if you do that. Wipe off the existing redgard first (not to remove the redgard, I mean to get it clean).



Thanks for the reply. He actually wound up just putting a skim coat of the thinset on the wall (and then on the tile as usual) and it adhered just fine. Thank goodness! We realize most people don’t wait EIGHT YEARS in between steps. Thanks again!



Can I tile (pebble on mesh) and grout the bottom of my shower?



Hi Torin,

I’m not exactly sure what you’re asking me here?


James (in NC)

Hi Roger,

Subfoor question:

Currently there is 9 foot span of 2″x10″s with 1″x4″ boards laid on a 45 deg as a subfloor in a 9’x28′ room. (house was built 30 years ago.)

I need to replace the 3/4″ plywood that is on top of the 1×4 boards.

To provide a stable base for tile my plan is: two layers of 3/4 ply glued and screwed together with Ditra Heat over that for a kitchen.

Does this sound sufficient for large format tile?

Any suggestions or corrections?



Hi James,

You want to put down the first layer screwed into the joists, then the second layer only screwed into the first layer (not into the joists), not glued. Then your ditra heat and everything over that.



Hi Elf

I just uploaded a couple of pictures. I have a rotted out subfloor near a tub underneath some Ditra mat. My plan

1) pull up the tile until the sublfoor is not rotted
2) Flap back the Ditra mat, scrape out all rot
3) Lay down 1.2″ backerboard (thinset on the bottom, backberboard screws
4) Clean out the crusty spooge from the Ditra waffles
5) lay down the ditra board on the backerboard (thinset)
6) Replace tiles
7) Grout the tiles
8) Caulk the tile/tub line
9) Finish the drywall (with backerboard)

Get high fives all around

What’s wrong with my plan?



Hi Will,

You need to replace the subfloor with plywood, not just backer. Once you do that just replace everything over the top of that with whatever is currently under your existing tile (ditra, etc.). If you want it waterproof, install kerdi-band over the ditra seams in front of the tub.


harvey fernandez

Hi Roger, im a noobie in tile installation and my 2nd bathroom came out pretty good. I am ready to conquer my whole house floor and I have about 3 layers of tile i have to demo. I’ve already started but the thinset is yet to be removed. Any suggestions on making this back breaking task a little easier. I have a bosch demo hammer that i removed the tile with. I also got one more question. I have a sunk in den, if the tile i choose does not fabricate rounded ends is there a tool or how would i make the corners rounded where the floor drops to meet the sunk in den? Thanks in advance for your help……



Hi Harvey,

The easiest way to remove cured thinset is to remove the substrate it is bonded to and replace it. Otherwise it’s a matter of scraping, and it’s a long tedious process.

You can get a bullnose blade and polishers for your tile to create bullnose (and spend about $1200) or you can google ‘bullnose fabrication’ for your area and have a professional do that for you much more affordably.



In one of your comments you said not to use redguard in a steam shower. Why not? my husband plans to redguard the backer board.



Hi Mary,

I may have said not to use redgard alone (it requires a moisture barrier behind your substrate), but redgard is completely fine in a steam shower.



any good suggestion on how to addresss insulating around a build in shelf in an exterior wall?



Hi Henrik,

About the best you can do is use wedi or kerdi-board. You are limited on space and they add a (very) little r-value. Enough to keep your shampoo from freezing, anyway.


lauren manasse

Hi – you were recommended to me to contact re: thinsetting a glass tile insatallation into a subway tile shower that is getting put in. The tiler is saying that he cannot thinset the installation without recessing the installation because it is flimsy and the grout/mortar will bleed through the tiles if he tries to mount it flush to the subway tile. Is there a best way to install something like this? I am not sure I like the way it will look if the installation is slightly recessed…. I can give you more info if it wold be helpful.THANK YOU!



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