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.


Hi Roger!
You are my personal DIY hero! I purchased your traditional waterproofing bundle, and visit your site almost daily (lots of reno work), but I can’t seem to find instructions on waterproofing/prepping for a window in a shower wall. If you could let me know where to find the information- or provide instructions on how to waterproof (both traditionally and with liquid membranes) and prepare the surface for tile (backer board) I would really appreciate it! I can sort of apply the instructions for a niche to the situation – but I want to ensure I am not missing anything. Thank you so much for your site and e-books!


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We currently have a large number of premium CPM campaigns we can run together.


joel gardner

I live in Toronto Canada where the building code says that I must use a continuous vapour barrier on all exterior walls (plastic container put beer in).
For the substraite I want to use cement board (DensShield preferably) and then waterproof over it (giving me a bag inside a plastic container to put beer in).
Is this too many moisture barriers?
Will it trap the moisture?
What is your recommendation?
What backer board do you think is best? (I need to match it to green drywall).



Hello Roger,
My husband and I just installed 1/4″ hardibacker board and are getting ready to put down 6×24 wood grain porcelain tile with modified morter. I read that on your blog :) The tile is rectified and was going to go “groutless” but I am told that there is no such thing and that I need the minimum of 1/16″ grout line. Where do I even start.?? My entire 1st floor 850sq ft is being tiled. I was thinking when you first enter my front door, to draw a line straight back and that is where my first row would go. Then stagger them like real hardwood. But do I start at the door or the furthest wall? The tile color is gunstock, what grout color would give me the most real life “hardwood” look?

Thank you!



One more thing I wanted to add: I read the Hydroban instructions thoroughly AFTER encountering this problem (yeah, I know…) and was surprised to find that they say it is cured enough for flood testing after two hours when the temp is 70F and above, and it is cured after 24 hours when the temp is between 50 and 69 degrees F. That is the strangest chemical curing timetable I’ve ever seen.



Thanks Roger,
I did not lose any water up to that point in the test. I dried it out, cranked up the room temperature to 72 degrees and have re-applied the second coating. A nice edit to your manual would say something about these blisters if they are common. The color change you mention doesn’t bother me at all, but the blistering was too much! The technical support guy from Laticrete responded to the same question saying I shouldn’t wait so long between coats. Maybe you should have his job! You mentioned temperature and humidity differences while the hydroban cures…maybe its a good idea to match the temperature of the test water (mine comes out of the tap at 50 degrees F) with the ambient temperature of the room to avoid such a large difference. Anyway, I think I am back on track with the project. Thanks again!



Roger, I need some advice. I bought your manual and followed it to create my shower stall. I just flood tested the installation, and after about 14 hours noticed that the second coat of Laticrete Hydroban was delaminating from the first layer. I used the trowel method to apply the Hydroban, and there is water between the layers but the first layer appears to be tightly bonded to the substrate. I let the first layer cure for three days before applying the second layer, and let the second layer cure for about 16 hours before flood testing. All drying was at approximately 65 degrees. I have peeled off as much of the second layer as I could, and pressed the water from between the layers. How do you recommend I proceed at this point? I read the Hydroban manual and saw nothing about waiting too long between coats though I suspect this is the problem. Oddly enough, those areas that I applied by brush (changes of plane and around the drain) are fine and the layers appear to have bonded together. The areas where I used the trowel to create and fill grooves for the proper thickness resulted in a problem. Thanks for your help.



Hi Dave,

It wasn’t water in the blisters. It was, but it wasn’t from the water you put in the pan, it was from condensation building as the hydroban was attempting to cure. Sometimes when the hydroban is applied that thickly at one time it will do that – it’s normal. I know, it still freaks me out too. That’s why your corners, where you put it on less thickly, are not doing that. Unfortunately you peeled it up and now need to go over it again.

If it does it again – IT’S FINE. Do not peel it up. You did not lose any water in the test, did you? As long as that’s the case then your shower is completely waterproof. The bubbles in the top layer did not show up because water seeped into the top layer, they showed up due to temperature and humidity differentials above and below the layer, moisture coalesced and formed blisters under the top layer. The layer was not compromised.

All liquid membranes can do this, it’s normal. they may lighten in color, too. And yes, that still freaks me out too. :D



Hello Rodger,

After receiving much conflicting info regarding my shower retro from a plumber, a tile guy, even a builder, I decided to purchase your “traditional method” e-book and am now convinced more that ever that I need to properly install a liner pan in this early 70′s recessed slab on grade home. Here in FL, as I’m sure you know, it is still not common practice to install a pan.

I have uploaded two photos in the reader’s projects area for you to reference. Background … I had my plumber dig out the old drain/p-trap last week and install a new 2″ pipe and a 3-piece drain. The trouble is when he did this I was still drinking the kool-aid and was not planning on installing a pan, so he put the bottom part of the drain flush with the rest on the concrete floor. Because of this, I find it hard to imagine how I will get any deck mud remotely near the drain when I make the preslope, which btw, isn’t going to be very tall at the perimeter anyway since the longest corner-to-drain center only measures 25″. That’s only about 1/2″ high at the perimeter if I follow your math correctly. Short of having the entire drain dug out again and raised, I would like to hear your wise feedback. Thanks!




Hi Scott,

Just run your preslope down to the edge (maybe about 1/8″ high around the drain). You can still make the perimeter as thick as you’re comfortable with, it needs to be a minimum of 1/4″ per foot, you can have it 1/2″ per foot. Once you put your top mud deck on you can make it thicker at the drain (3/4″ – 1″) and rise 1/4 / foot to the walls. It won’t be a consistent slope over the liner, but it will still be 1/4″ per foot and your preslope will still drain (REALLY well). :D



I am planning for a floor tile installation project. I see 2 different length of backerboard screws in Lowes store: 1 1/4″ and 1 5/8″. Which type should I use? Is the screw length chosen according to the backerboard thinkness that are 1/4″ and 1/2″, or according to the thinkness of the subfloor underneath the backerboard? Please advise.



Hi Yvonne,

It is chosen due to the application. 1 1/4″ work on walls, but I use 1 5/8″ for everything unless I’m using 1/4″ on walls, they work for it all. Your subfloor should have a minimum of 1 1/8″ substrate beneath your backer. If you don’t then 1 1/4″ screws will work.


amy rodgers

I want to build a shower like the picture on your library page. I have own curved shower doors and want to make a shower to fit my doors. I want to buy a book from you and did review your ebook. I want to ask what method should be used for the floor. My shower curb with be curved and I will be placing a liner drain (36”) towards the back wall. So yes my slope will be to the back. I love your brick idea to help design the curb.



Hi Amy,

Those pictures change every time the page is opened. However, with a curved shower perimeter your best (and easiest) option is liquid waterproofing membranes like hydroban or redgard, second best would be kerdi.



Mr. Elf,

Can you please post a pic or give a brief description of what a ceramic tile would look like if a cast iron pot fell on it?

I saw what an improper installation looks like on your pic, thank you!!
I belive it will shatter in multiple areas, another person is arguing that a hairline crack (like the one in your pic) is a result of the falling pot.

Any input is appreciated.



Hi Andy,

Sorry, I haven’t dropped a cast iron pot on tile for a couple of decades now. :D It will look like the impact point of a shattered windshield normally, but it could be a crack. The crack, however, will have a larger chip at the impact point.



Hi Roger,

Sorry if this is long.

I’ve spoken to about multiple highly rated tile contractors in my area and they either don’t know what a soft joint is or insist that I don’t need them. The project is about (1000sqft-1200sqft) for new construction on a concrete slab.

Everyone at John Bridge agrees with you that a large tile install needs soft joints. Not to mention the TCNA and everyone who manufactures tile products.

So my question is this: should I just go ahead and have them install the tile without soft joints or am I better off getting hardwood if I can’t find someone who will do it right? Is it inevitable that the install will fail without them?

Thanks so much for all your help. It is very appreciated.




Hi Danielle,

You are better off hiring someone who knows what the hell they are doing. :D Do you need brakes to drive a car? The answer is no, you don’t need them, the car will drive just fine without them, you just can’t stop. Soft joints are REQUIRED for a successful installation. If they don’t do them, or don’t want to do them then move on to someone who will. You’re the one signing the check, no? If you have to teach them how to do their job correctly then that transaction seems backwards to me.

Check here for a qualified contractor: NTCA


Kevin Chisholm

Aloha….just me again…I was hoping you had cracked the code of misleading sales people and those who think they know but don’t. Your site seems to be the only one without a hidden agenda. As a reminder, I was wondering if thin set will stick to hydrostop flat roof covering. I have gotten so many answers and like most people I’ve heard the answer I wanted to and am hoping its true…several tile guys have said they do this on a regular basis. The very thin membrane that is laid down first is like a thin schluter Kerdi product, then two coats of a latex coating (rolled or sprayed on)to help make it waterproof and reflect the sun. I want to lay tile over this product so they can use the roof as a sun deck . Mahalo for your time and knowledge.



Hey Kevin,

I have no idea whether it will or not. There is no sheet on it for that type of application and I have never seen the product. If it is indeed a kerdi-like product, why not just use kerdi? It will waterproof it and save you height as well. Thinset may or may not bond to it, and it may or may not do that for a long period of time. Without a tested application, which they would do it there were money in it, then I wouldn’t trust it to last long-term. If the purpose of that membrane is to waterproof a roofing application I would be inclined to use a tile-specific membrane manufactured for that same purpose.


Kevin Chisholm

thanks for your input, the schluter rep said their product isn’t made to go over borat/preasure treated plywood. I’m thinking of using just the first fabric embedded layer of the hydrostop then apply ditra and kirdi the joints to make it waterproof. this way a bed is made between the plywood and the ditra, there is a texture just like when kerri is layer so i think it would bond and then with the tile of coarse would stick fine to the ditra. Thanks again for your help



Hi Roger,
Layout back shower wall.
I want to install 12×12 tile in shower, sides wall are 36” width and back is 40”
How should I install tile on back wall:
1. 12,12,12, and 4”
2. 8,12,12,and 8”




Hi Yakov,

Center it. 2 12′s and 2 8′s.


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