Tile is NOT Waterproof

by Roger

A common misconception about tile and grout is that they are waterproof. Once you install tile in your shower you have a big waterproof box that will last forever. Ummm, no.

Tile and stone (as well as grout) will actually retain water. How much water it retains is directly related to the density of the tile. For instance, porcelain tile is much more dense than travertine. This means that travertine will retain more moisture and allow more water to seep through  to your substrate. If you happen to have travertine in your shower – don’t panic. As long as it was installed properly it will be fine.

So how do they figure this out?

When a specific type or brand of tile or stone is manufactured for production, the company will determine its density. There are four different categories into which each tile may be placed.

This is determined by weighing the particular tile, submerging it in water for a period of time, then weighing it again. The difference in the two weights determines the density or absorption of that product. Basically how much water it holds. It will then be placed into one of the four categories.

  • Non-vitreous: These are tiles that absorb 7% or more of its body weight. These are for indoor use only, normally on vertical surfaces such as backsplashes and wainscots.
  • Semi-vitreous: These absorb between 3% and 7%. These are also for indoor use only.
  • Vitreous: Absorb between 0.5% and 3%. These tiles may be used for interior and exterior applications.
  • Impervious: These are the most dense (porcelain) and absorb between 0.001% and 0.5% of their weight in water. They are suitable for all applications.


Depending upon where you intend to install the tile you may need to consider this. In most cases it’s not an issue. Only in the most extreme or unusual circumstance will you need to take into account the category of your particular tile. A tiled patio in Alaska, for instance. If you have a tile that absorbs a considerable amount of moisture and it freezes, well, you’re gettin’ a new patio.

The biggest factor to consider is the amount of water to which the tile will be exposed. (Along with the possibility of freezing, of course.)  For anything up to and including a regular shower, it isn’t necessarily an issue. These applications, using proper methods, should be at least water resistant before a box of tile is even opened.

Why is this an issue?

With any tile application, the durability of the tile will be only as good as what is beneath the tile! Let me say type that again – that again.

If you have a wall in your shower with just plain drywall and you stick your tile to it, it may look good for about a year. It may look good for much longer. But, if moisture gets behind the tile (and it will) through the drywall, to the framing studs, well, you’re screwed.

Your framing studs are (most likely) just simple 2 X 4′s. If even a minute amount of moisture from your shower reaches it all hell’s gonna break loose. Common studs will do what we call “wick” moisture. It is aptly named because it acts just like a candle wick (tile guys are simple folk).If you place one end of a candle wick in water the other end will be soaked in short order. Wooden studs do the same thing.

Think of it as a water highway. The water will simply continue along that same path until it finds something else to soak into. That something else is more wood. When wood gets wet it . . . wait for it . . . swells. Normally that swell has only one place it’s going – right against the drywall and into the back of your tile. Tile’s will crack, grout will crack, your patience will crack, and the end of the world will be right around the corner. You get the idea.

This is not (normally) a subject that needs to be considered when installing tile on your floor. A shower (or other wet area) is unique in that it is subjected to a great amount of water on a regular basis. Unless your kitchen is a swimming pool you really don’t need to be that concerned about it.

Just understand that tile and grout are not waterproof so care needs to be taken to eliminate as much moisture from the surfaces as is realistic in any given application. You know – don’t make your kitchen floor a swimming pool.

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ARUN

hai , recenly i have procured ceramic tiles in a lighter shade for my bathrooms,within 2 months after laying , some wet patchs are spoting on the tile glazing surfare . so kindly suggest me as to how to solve this issue without re doing the tiling .

Reply

Roger

Hi Arun,

It sounds like an absorption issue with your particular ceramic. That means you can not solve the problem without replacing it with a different tile.

Reply

CFitzpatrick

Hi
We have a terrace which is actually a roof on a garden room beneath – (specially built for this purpose and to allow us to walk on it and use patio stones.) We have EPDM rubber roof material on top of a felt and a concrete screed.
Can we use porcelain tiles – sitting on special plastic or rubber feet or pads for the top? Can you recommend any 600mm square with a non slip surface?
Many thanks
C

Reply

Roger

Yes, you can, if you can find them. The slip rating of the tile will be labeled as the coefficient of friction or static coefficient of friction (COF, SCOF). The higher the number the less slippery the tile.

Reply

New Tiler

Hello Roger,

I purchased your book. There is a lot of great information in both your websites and books.

I’m about to redo a standing shower in one of our bathrooms that the original tilers did incorrectly (no waterproofing on the walls). I’m going to so with the liquid barrier over concrete substrate.

My question is this: My wife and I found a particular tile we want to go with. It is ceramic and non-vitreous. Would this tile be okay for the shower walls?

I’ve read previous questions form others about whether or not a particular tile is okay, but the others refer to porcelain tile.

Thank you.

Reply

Roger

It’s fine.

Reply

Jeff

I have provided a link to a ceramic tile I would like to use in my stand-up tile shower. Would like to know if these tiles would be ok? Also, do you need a rubber membrane on the walls or do you just use the rubber membrane on the tile floor of shower? Any advice would be great for the proper protection from the moisture (like what is needs for the walls and the tile floor). thanks, Jeff

Reply

Jeff
Roger

Hi Jeff,

Yes, those tiles are fine. If you download my shower waterproofing manual it will explain to you the different methods of waterproofing a shower and what to expect with each. You can find it here: shower waterproofing manual. The ‘rubber’ membrane is used only for the floor.

Reply

Kyle

Hey Roger,

I was wondering if it would be okay to use semi-vitreous tile around the walls of a shower. Not the floor, just the walls. There is a tub in there.

Thanks,
Kyle

Reply

Roger

Hi Kyle,

Yes.

Reply

Sunny

Hi Roger,
My problems have just started,I live in a place where it rains too much and the sun too harsh,that’s not the problem,it is that I had tiles fixed on the roof which have now started leaking in some places so as a safeguard I got grouting done again,but it has landed me in more trouble now,actually started to leak at more places,kindly advise,should I take all of them out or there is some kind of coating which can be done on these tiles so as to make them waterproof.
Would really appreciate your suggestion.

Reply

Roger

Hi Sunny,

I’m not real familiar with roofing tiles, but I’m fairly certain that, just like a shower wall, the waterproofing lies beneath the tiles. There is no product which can be put over tile that makes it waterproof long-term – I’m fairly certain that applies to roofing tiles as well.

Reply

Sue

Hi Roger, Thanks for your website. It is full of useful info. I live in a concrete condo and I want to tile my bathroom floor which is concrete. I found these porcelain tiles with these ratings:
Water Absorption: Semi-vitreous
Dry Coefficient of Friction: 0.98
Wet Coefficient of Friction: 0.56
Tile Thickness: 8mm
Tile Finish: Glazed

My concern : is “semi-vitreous” safe for bathroom floor which can be steamed up or occasionally get water drops. What does dry and wet coefficient mean? Do I need to get impervious tile for my floor?

Thanks you so much for all your advice. Sue

Reply

Roger

Hi Sue,

That tile is just fine for your bathroom. Static coefficient of friction is a measure of how slippery your tile is. Anything around .5 or .6 wet is just fine for a bathroom floor (the higher the number the less slippery). You do not need an impervious tile for your floor.

Reply

A & C

Hey Roger,

My husband and I are in need of your expert advice. We are wanting to tear out our builder grade carpet, which pretty sure has no padding and lays on on a concrete slab and replace with some sort of tile. We have decided to do this because we have dogs, one which we have found out is diabetic and the other a male maltese pup (both = pet messes and we are working on both to get them better) but in the mean time they have completely ruined the carpet. My husband and I really like the look of travertine but we want to do whatever is best for this high traffic accident prone area. We want and financially have to get it right the first run through. So can you please give me your list of great tiles to use for this area and pretty much a breakdown of how it should be installed correctly and the best products to use. Also for our basement how to you feel about the stained design concrete? Does it hold up well to pets and high traffic as well? We would greatly appreciate your response and thank you for your time.

Reply

Roger

Hi Carrie,

I would use a porcelain tile there. Any natural stone is prone to etching by acid (uric acid) and will eventually begin to degrade. Porcelain will hold up. I would also use ditra or strata-mat beneath it over the concrete.

Reply

JD

Hi-
We have pressure tested the shower in our tub and determined our leak is not due to plumbing. We have a tub installed with tile over hardi cement board. Many contractors have told us we don’t need a waterproofing membrane over the cement board behind the tile. We currently have water leaking thru to the cement board (we ripped out part of the wall to view it from behind and we see the water traveled down to the tub flange/channel and leaks out at the tub edge). This is why our caulk line at the tub always stayed soft/mushy and degraded over time because water was constantly sitting in this channel along the tub edge.
What I would like answered is this, 1) if the cement board had been waterproofed with a product, wouldn’t the water still pass thru the grout and then hit the water proofed cement board (instead of being absorbed by the cement board) and still travel down to the tub flange and soak the caulk line, accumulate, and still spill out over the tub edge behind the walls? 2) The tile design consultant said yes, the water would still go thru the grout lines, hit the impervious membrane and roll down into the tub channel and then “spill back” into the tub itself thru the caulk line – which i find impossible to believe. It seems that situation would be no different from what we have happening now, but it does not “go thru” the caulk into the tub as she says it should, it spills out behind the tub.

Reply

Roger

Hi JD,

1. Yes, it will still run down and out of the tub if you don’t install weep holes.

2. Same answer as above.

3. NEVER ask a designer HOW things WORK. Only ask designers HOW things LOOK. :D

Reply

Kerry

Hi Roger,

I’m building a shower and planned to use Leonia Silver Glazed Porcelain Mosaic Subway tiles on the shower walls. I just realized they are not impervious (they’re semi-vitreous.) Should I forget these tiles & find something else? I’ve been looking for impervious tiles, but it’s not usually a search option.

Reply

Roger

Hi Kerry,

You don’t need impervious tile in a shower. It is a verifiable classification for tile, but is used oftentimes to upsell something that really isn’t needed. The substrate behind your tile needs to be waterproof, the tile doesn’t (that’s what an impervious classification means). They will be fine in your shower.

Reply

Andrew

Hey Roger,

I have used the leonia sands glazed porcelain tile as well in a bath/ shower surround. Should I seal the tile as well as the grout?

Thanks

Reply

Roger

Hi Andrew,

It’s not normally necessary with porcelain, but it won’t hurt at all.

Reply

P

Hi Elf,
very useful info, thanks for that. I want to know if i can use 12×12 porcelain tiles for shower/bathtub walls, or what do you recommend? thx

Reply

Roger

Hi P,

Yes, you can use porcelain on your tub walls. Porcelain is what I recommend.

Reply

CLAIRE

HELLO
we have just finished tiling our shower and used BAL waterproof grout (suitable for showers and swimming pools) as well as BAL waterproof adhesive. It has been fine for 3 weeks – however, today my 2 small sons had a shower consecutively – they were pretty much spraying the walls for 20 mins – and the downstairs flat had some drips coming through direct below. Clearly this is the shower…. and we now realise that we should have used some sort of product to waterproof the walls underneath. However, we really don’t want to re-tile – it took us ages… The BAL grout says it is waterproof for 15 mins – so OK for a “normal” shower and not if a 2 YO and 4YO spray the walls!! Would be good to have your thoughts.
Thank you

Reply

Roger

Hi Claire,

I’m not familiar with the BAL brand of anything. I do know that yes, your shower walls should be waterproof behind your tile, but a bit late for that. :D About your only option is to not let them do the 20 minute thing. There isn’t anything that you can put over the front of the tile to make them waterproof. If it helps they’ll definitely grow out of that. In about 5 years you’ll need to tie them up with duct tape and lock them in there. :D

Reply

Diane

Hi Roger,

We just installed a kerdi shower system, tiled everything, and almost ready to start sealing/grouting. The tiles on the shower walls are porcelain, and the tiles on the shower floor are 2×2 stone mosaics. We’ll be using a urethane premixed grout that already has sealant built in (Bostik product).

I have a contrarian husband who now thinks that by sealing the 2×2 stone mosaics and the usage of the Bostik water-resistant grout, we’d be “trapping” any water that’s between the shower tile floor and the kerdi membrane. Hence, he wants to leave the mosaics unsealed, and let it stain naturally. Is there any merit in the statement of water being trapped if we go ahead and seal the 2×2 stone mosaics?

Thanks,
Diane

Reply

Roger

Hi Diane,

Tile and stone sealers allow moisture to dissipate – they are not waterproof. That’s why they aren’t waterproof, a tile installation needs to allow vapor dissipation above or in front of the waterproofing so natural stone doesn’t spall. Sealing it is fine.

Reply

Stephanie

Thanks for all your information on this site! We bought our first house in March and our first big project is to add a shower on the main floor, where currently there is only a half bath. It will be a corner shower with an acrylic pan and tile walls. I found tile that I like for most of the shower and it is a porcelain. The tile I bought for a border is tumbled slate. Is it okay to mix these two materials? When I seal the slate, should I seal everything, or just the slate section? Is the tumbled slate a bad idea and should I just find something else to use?

Reply

Roger

Hi Stephanie,

It’s fine to have both in the same shower. You can seal everything if you want, not necessary though. Tumbled slate is fine for a border.

Reply

Sara

Hello,

We moved into a 75 yr old mediterranean house that has a fountain/pond in the entryway. The inside is tiled with porcelain tile about 2 ft. tall and is I good condition (no cracks or missing grout).

My question is that we have no idea how it was water proofed or if it was waterproofed. We retiled the bathroom showers and there were lead shower pans in there, but I’m not confident in assuming they would have used something in the construction of the pond for a water barrier. There is no evidence of any water damage/leaking in the past (adjacent tiles lifting, etc…) but I want to find out if there is any sealer I can put over the tiles and grout to waterproof it to be safe? Could I paint a marine grade epoxy over it?

Reply

Roger

Hi Sara,

There is nothing that you can put over the face of the tile which will make it waterproof. You can put epoxy over it, but it would likely yellow over time. Most of it is not uv-neutral.

Reply

john seiter

Bought your book about shower prep. Good job. My problem is that the plastic barrier does not stick to the silicone around the flange of the base. It sticks to the base but not he black plastic. Can I go ahead and put up the backer board and tile anyhow?

Reply

Roger

Hi John,

Yes, it should create like a gasket behind your backer. I don’t understand why the plastic won’t stick to the plastic, though. Never had that problem.

Reply

renee

So I have been reading your site and have received lots of information but I have a question. My bathroom is getting ready to be redone for the third time (not happy) due to contractors not doing their jobs. The first time the cocking was not installed properly and while we were talking showers the regular sheetrock was getting wet, within 1/4 inch of the ceiling. My builder fixed it no problem. Then a year later the soap dish fell off the wall, so they came back in and found out that the installers did not install the tiles properly. So now I have mold growing behind the wall again and mold under my floor. The builder told me that is was because I have not taken care of my shower. Then it was because I was not closing the shower curtain and now I just don’t know what his excuse is, I have put a sealant on the grout every 6 months and I don’t use harsh chemicals to clean so here is my question. O I must say that there is blue board in there with no waterproofing.

If the tile was not installed properly could that cause the grout crack (too much water to thick of lines 1/2 inch)

If there is no waterproofing on the blue board can that be a cause for the floor to be damaged

Thanks

Reply

Roger

Hi Renee,

Blueboard is not a waterproof substrate. Water WILL get behind your tile and grout – they are not waterproof. Your shower should be completely waterproof before any tile is installed. If there is mold it is because the substrate (blueboard) is saturated. Yes, it will migrate to the floor, as well as your entire wall cavity. That shower needs to be removed and one which is built and waterproofed properly put in it’s place.

Reply

Greg

We just bought a 10 year old home near Pensacola, Fl. There is an outdoor balcony with the floor surface being Travertine tile. There are many long cracks in the tile, along with a few holes. After periods of rain we see water leaking from the wooden beams underneath the floor of the balcony (which is the ceiling of a balcony beneath the upper balcony). Not a lot of water, but a steady drip. Is there anything I can do to prevent this short of removing the tiles and seeing what’s beneath them? Thanks

Reply

Roger

Hi Greg,

Not really. It is indicative of an installation that is not properly waterproofed, but until you get into it to find out how it was built, and fixing it, there’s not really anything you can do to prevent it.

Reply

Elizabeth

Hi,

Thank you for your great website.

We have had a problem with out kerdi shower installation. We apparently did not get the drain low enough (we used the kerdi shower base form), the result being a shallow swimming pool that grows slimy things. We have tried drying the shower after every use (a real pain when there is so much water), but it still does not dry out even within a couple of days of being unused. We are now losing our gorgeous sicis glass tile and the mortar underneath is very soft (can remove with fingernail).

How far down do we have to go to repair this? Do we have to tear everything out down to the hardie backer walls or can we scrape down to the kerdi on the floor, pull it up and mud a correctly sloped drain, re-kerdi and tile?

Thanks for any ideas,

Elizabeth

Reply

Roger

Hi Elizabeth,

You should be able to just remove enough around the drain to remove and reattach it properly, then tie in your waterproofing (kerdi-fix and 2″ overlap) and retile.

Reply

Innocent

Roger,
I and my team just finished building a pool-like structure that is supposed to serve as a fish pond. It measures about 4 ft above the ground. It all came to a near disaster when we found out that all the 4 ponds is leaking water real fast. What amends can be done now?

Warm regards.

Reply

Roger

Hi Innocent,

Vague much? :D

The easy answer is that all you have to do is fix your waterproofing. That’s it. However, without knowing how your structures are built, what type of waterproofing you’ve used, how it was installed and how it’s leaking (a corner – a seam…) I have absolutely no way of telling you how to begin doing that.

Reply

Michael Helms

Roger:
I pastor a church that has a tile baptistry. It has been leaking for a couple of years and we have been trying to repair the leak. We finally discovered if we did not fill the pool up as high it would not leak. Today it leaked again. I thought it wasn’t leaking because of the rubberized spray we applied but I think we had too much water in the pool. From reading your sight, are we in danger of the pool falling apart now that it has leaked several times? Is there a material we can purchase to apply to the tile to seal it to prevent it from leaking?

Reply

Roger

Hi Michael,

Unfortunately there is no product which can be placed over the face of a tile to make it waterproof. Tile is simply a decorative covering for a waterproof substrate. If you have a leak it will continue to get worse.

The deal with it not leaking unless filled up to a certain point likely had more to do with pressure equalization than the location of the leak. Once the saturation of the substrate became wet enough it began to suck water out of the basin. When you filled it up before the pressure of the water forced water into the spot of the leak. Once the substrate became saturated enough, it didn’t take that much pressure to get it to leak again. I’m afraid the only viable solution is to rebuild it.

Reply

CC

I have a question in regards to my shower: My shower floor is tavertine tile and while cleaning I noticed that one of the tiles has a hairline crack in it and then it ran through the grout and half way through the next tile. These tiles are up against the wall on the floor. What could have cracked them? Do they need to be replaced? For now I have filled and sealed them-my concern is water/moisture.

Also, I noticed where the floor and wall meet on one side of the walls in shower there is a slight dip in the center, so it is not straight from end to end. Also, water tends to pool up in this area as well-it does drain slowly once the shower is turned off. Is this a concern?

Reply

Roger

Hi CC,

I don’t know what could have cracked them. Well, I know all kinds of things that could have cracked them, but can’t really venture a guess without knowing a lot more about the substrate beneath the tile.

If the waterproofing aspect is what you’re concerned about – don’t be. Your tile is not waterproof. Your shower floor beneath the tile should be, but the fact that you have hairline cracks does not make it less waterproof.

As long as the water does drain it isn’t really too much of a concern. If your slope beneath the tile doesn’t drain, that would be a concern. If that were the case you would notice the grout in that area remains dark constantly and never dries out.

Reply

sarah

thank you Roger ;)

Reply

sarah

Hi this is quite embarrassing, but, it is what it is. So here goes, my husband is putting a kitchen backsplash in for me and has left me with all the prep work we “inherited” a bunch of nice tiles from my parents which were outside (weathered) and I decided i was going to clean them thoroughly well me being the bright blonde that I am soaked them in warm soapy water and now they have absorbed a massive amount of water. My question is have I ruined these tiles or is there a possible way to dry them to avoid mold etc… . Thank you and again quite embarrassing. :/ Perhaps stick them in oven??

Reply

Roger

Hi Sarah,

It’s no problem at all. Just let them sit around for a day or two and they’ll dry right out. You can put them in the oven, but it isn’t really necessary. Some ceramics have a high absorption level, they soak in a lot of water, but they’ll dry out with no damage done.

Reply

Aamer

Hello Roger,

I’ve been struggling with a few methods our contractors used in building our tub/shower surround walls in one of our bathrooms. This is the first time my wife and I have ever had anything remodeled in our home…needless to say we are rookies and we are learning a lot as the work progresses :bonk:. Please HELP!

So here is the situation in the sequence of events (my questions follow the list below):
1. We had them rip out the old tub and fiberglass wall covers around the tub. When the fiberglass was removed, we found the “green” drywall all the way up to the cieling.
2. The contractor proceeded to cut a 2-foot wide strip of the green wall around the perimeter of the tub (3 walls), exposing the studs…I’m not sure why, however?
3. He replaced the strips of green board that he cut with strips of hardibacker.
4. He covered all 3 surround walls with RedGard from the ceiling all the way down – he covered the green walls and the hardibacker panels.
5. He taped the new seams (between the new hardibacker and green wall) and applied thinset.
6. He did *NOT* apply RedGard over the thin set to seal the seams. :wtf:
7. He then proceeded to install our SLATE tiles on the entire surround all the way upto the ceiling.

QUESTIONS:
1. ALthough not the most ideal methods according to various forums I’ve visited, do you think his method is ok?
2. Once the slate is fully grouted and sealed properly, in your opinion, do think water would eventually penetrate through the slate tiles and seep into the un-RedGarded seams?
3. To maximize waterproofing, is it safe to use a clear acrylic laquer of some sort to “waterproof” the slate and grout so water is prevented from penetrating the slate?
4. Am I overthinking the situation? :-?

Your expert opinion would be MUCH appreciated…and keep me from losing more sleep!

Best Regards, Aamer

Reply

Aamer

****when I wrote “water” above, I also meant “moisture”..I was using then synonymously.****

Reply

Roger

Hi Aamer,

1. No, I don’t think it’s okay. I’m not sure why in the hell he would have left the greenboard up there, did you ask him? It will likely be fine, though. It’s a hell of a lot better than having no waterproofing.

2. Yes, it could. I don’t know that enough would get back there to penetrate into the wall cavity before evaporating. I simply don’t know, no way to tell. Sealer isn’t gonna stop it, that’s not what it’s for.

3. No. Any type of coating you put on your slate will end up not allowing the installation to ‘breathe’, which it must do. It may yellow over time and may be detrimental to the stability of the stone. Sealers breathe, but they don’t waterproof anything. They are used to make things stain-resistant and easier to clean.

4. Maybe. :D Only you can answer that.

Reply

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