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.

Danny Brewer

I have a tolerance question. We are installing 1 foot by 2 foot rectified tile over drywall in bathrooms. We checked the walls for plumb and flatness and where the seams are at studs some are bowed at least a quarter to a half inch. What is acceptable tolerance? The tile is getting quadec at the top. I don’t see anyway to do a professional job without tearing out drywall and fixing it. Any thought or advice would be welcomed.


Dean T

I am laying 13 x 13 porcelain tiles over plywood subfloor with engineered joists 16” OC.
I am using Ditra with a modified thinset on the plywood and Bostic Ditra-Set to set the tile.
I bought the Ditra $trowel$ for setting the Ditra and I am using a ¼ x 3/8 trowel for the tile.
I sanded the plywood to remove paint and drywall compound that was under the carpet and level out any high spots, set nails below the surface and added deck screws every 6”-8”.
This is a hallway and laundry room upstairs so I will be doing small sections over time. I’m going diagonal so lots of cuts
Should I seal the plywood or just dampen with a sponge before setting the Ditra?
My floor is fairly flat however there are a few places where the tile wobbles a bit. When I push down on one side the opposite side raises a little less than 1/8”. Will this be a problem or will the trowel size I am using allow the thin-set to compensate? Hard to tell if I have a high spot or the beginning of a low spot as the floor is slightly out of level (<1/2” in 20”). I really want to avoid SLC because I may just create more problems than I solve.
I had heard some people prefill the waffles so I was thinking of doing that so I can pay extra attention to filling them correctly and speed up the process when I set the tile. If I pre-fill the Ditra and loose-lay the tile on top the next day will it cause any problems to walk on the prefilled Ditra under the tiles to set the tile later? I had heard it is not a good idea to walk on the Ditra without prefilling because the waffles can get crushed.

Thank you,



We grouted our shower tile with white Spectralock Pro epoxy grout. Due to some installation errors, the glass shower door had to be moved and now we have 8 holes where the hinges used to be. We plan to fill the holes with the same grout, but don’t want little white dots in our grey tiles. We would like to avoid buying a whole Part C of the mini kit to create the grey color. Any suggestions on something else we could use to color the grout that comes in a small quantity?

Love your site, only problem is I get sucked into reading about issues I don’t have because your humor makes me smile.

Thanks for your help.



Purchased your Creating a Shower Waterproofed Floor and Walls with Liquid Topical Products. Enjoyed the information and sense of humor. Something mentioned but not explained is installing a linear drain. Also can you recommend how to build a shower bench?
I’m installing a shower over plywood and will use your manual as my guide. Easy to follow and cleverly written. I have 2 questions.

1.Shower dimensions to the studs is 4′ x 6′. Liked the idea of installing a 3-1/4″ x 36″ linear drain. A 58″ (+ or -) sliding shower door will be on the left side of a 6′ side. I’d like to install a 1′ deep x 4′ wide bench on the back wall making the actual floor 4′ x 5′. Where would you recommend installing the linear drain?

2. Also shower bench made of wood or chimney block covered with Durock and one of the liquid membranes? Suggestions on how to build?
Appreciate your advice.


Daniel Krum

Hi Roger I have been looking at your site here and want to purchase your manuals. Can the be purchased other than ebook? I would rather have a hard copy if possible and have to print it all out. Plus in your photos the book looks nice with a shiny cover. :)

I posted this on your facebook page too, sorry.



Question concerning unmodified thinset for kerdi membrane installation in shower.
I am having trouble locating any of the unmodified mortars you recommend in your discussion. Lowes stopped selling Kerabond but has “MAPEI Uncoupling Membrane 50-lb Gray Powder Medium Bed” which I think is unmodified. Any comments on this product.


bob walker

Hi Roger,

I just bought your manual for using Densshield. I also have the Kerdi one, but decided against it…the Kerdi membrane looks like too hard for a first timer and never going to doer again, and the Kerdi board…well…that foam stuff just looks weak. I finally found some Densshield in Phoenix and like the look of it, except the whole fiberglass in my armpits thing. AND I really like your manuals, to the point, not too long and don’t assume a guys knows a lot, but also not talking down to me either.

I am a Chemical engineer by trade, and a little bit handy, and my house was built in 1953. Remodeling the bath, have a new tub, and want to tile the surround. Me? Me and my wife would use pink 4.25 tiles again, but would have to sell the house for less when we retire, so modern it is. Hope this e-mail isn’t getting too long, time for questions.

By the way, they tub and shower at this house were mudded in. Now that is a tile backer.

I have the 2016 TCNA handbook, and am looking at B419-16. Questions are:
1) It says waterproof membrane optional? I assume it is OK to skip it? What is the down side.
– seems extreme. I will tell you, I tore out my bath surrounds in both my condo (built 1961) and this house and they used plain old drywall under the 4 1/4 ceramic tile and the walls showed water damage only at the plumbing fixture penetrations.
2) The drawing shows the Dennshield coming down over the tub vertical edge flange, just as your say. That is a whole crap load of cardboard shims to get it out that far. Not to argue, but if I do that, and add 3/8″ wide tile and the thinset, there will be little horizontal tub edge left.
– since the tub flange come up 1/4 inch, can I bevel the back edge of the Densshield no more than 3/8″ in from the back and fit it?
– alternately, if the Densshield hits the the top of the raised edge, but sticks out at least 1/4″ overlap, can I silicone under it, and bring the tile down to 1/8″ from the tub horizontal surface?
(If this is too hard with words, I can draw it.)
3) TCNA says not to have 4 corners of the Densshield meet.
– That makes my layout more messy. Is this critical? I dont think you mention it.

Thank you for your patience. Hope you can answer and really hope you can understand what I am trying to ask.

I can send photos if it helps your website.

Best regards,
bob walker
phoenix, az



Simple question, but I’ve seen contradictory information all over the place.

Is semi-vitreous ceramic tile (WA 7%) acceptable for use in a shower wall, given it is placed on a properly sealed substrate?

PS – I bought Tile Tips and Shower Sealing Guide but the bundled price link did not work and had to purchase each at the whole price.


Lori Peterson

I want to have 48″ X 9″ wood look porcelain tiles in my great room & kitchen. I have been told this size is more expensive to purchase and install and will break easier during and after being laid.
What are your thoughts on this please.



Hi – I just hired a tile installer to do some grout repair. Our toilet leaked and caused the grout around it to crack and flake off. While using the grout color samples to find an appropriate color, the installer said the final dry color was always lighter than the sample stick showed. So, he chose the next darker color, and I believed him, not having any grout knowledge myself. Well, after drying for 4 days, it is much darker. What can I do to lighten the new grout?



Hi Roger,

What are your thoughts on installing a Schluter niche, then installing 1/2″ cbu (with 1/16″ to 1/8″ gap between niche and cbu), silicone gap and once silicone is cured, Redgard the entire substrate including the niche. Will I have problems with movement between cbu & niche if I don’t apply the Kerdi band that’s called for or is the Kerdi strictly for waterproofing? Thanks


Please Delete

I can’t see the comments.. I’m typing one to see if I can see them once submitted. Please delete this comment.



Applied thin-set, 1/4″ backer-board (screws every 5-6 inches O.C.) – allowed to dry. Applied thin-set over backer-board, laid tile, then placed cement bags, boxes of tile, etc. on tiles. Was this a bad idea?



This is in regards to the remodel of small bathroom. We picked a tile project for our contractor that we initially didn’t think was too difficult. It is an L herringbone pattern. He has had so much difficulty in getting the grout lines to line up….to the point of taking them down and doing them over. Surely there must be some trick to this! No matter what he does, he says it “grows”. He suggested applying them with no grout line but we have read this is a big no-no. He has become very frustrated as are we. He has drawn it on the wall and it still grows the taller he gets the tiles. These are pictures. It looks pretty good when finished, but he still is frustrated and not happy. Can you tell us if there is something we are overlooking?




Being from Colorado, I’m hoping you can clarify something for me. How do you go about installing a poured pan in a basement with “floating walls”? In the standard process for a poured pan and tiled walls, I can’t figure out how to leave any room for movement.




Hi Rodger & David,

I have the same question for building a shower in the basement in Colorado with a floating wall. It seems that without leaving a massive expansion joint in the tile, a floating wall wont work.




Leave a Comment

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)