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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Shawn

Hi Mr or Mrs Floor Elf,
I read your article “Tile is NOT waterproof.” I found it very informative and interesting.
I have a problem with a house that I am buying and I cannot figure out a solution.
The wood floors in the family room are buckled. The seller says the wood was not properly installed and that she has been living with it in that condition since 2003, my gut tells me there might be some moisture. The house was build on a cement slab in 1978 in Los Angeles hills. I think there might be some moisture coming up from under the slab.

My questions is, if I tear out the wood floors and install tile, will that solve the problem?? Travertine??

I plan to use wonder board and insulation under the tile to act as a barrier. My wife thinks there would be mold build up underneath, but I don’t see that happening.

Would love to hear your thoughts.
Thank you in advance.
Anxious home buyer.

Reply

Roger

Hi Shawn,

You can not use wonder board on concrete. If you have moisture coming up through the slab I would use a product like ditra, which has vapor dissipation channels built into the underside of it. This will allow any moisture from the slab to evaporate and dissipate beneath your tile installation without affecting the tile itself.

Reply

Carol Ann

Roger,

I have been thinking about doing tile in my entire bottom floor on my two story home (not a basement). I love the look of the tile. I foster dogs. I had some fosters that found a spot in my dining room and urinated on the carpet, now all other dogs find that spot and mark it also. I have cleaned it to no avail. Would you recommend tile? Is there a way for me to water proof the grout? Since I foster the dogs it is very hard to predict who is house broken and who is not?!?!

Reply

Roger

Hi Carol,

Yes, tile would obviously be a better solution. You can use epoxy or urethane grout rather than regular cementitious grout.

Reply

Pat

Because of two, “100 year” floods, we have replaced the basement flooring twice in six years in our raised ranch. Now we are going to install porcelain tile down there. We NEED the living space. In the meantime our adult children are almost at war over the “temporary” living/sleeping arrangements.

Anyway, the tile I’m looking at is a faux wood plank style from Lowes. For the best look we will want very small grout lines. What’s the best grout to use (sanded/unsanded)–and do you have any other tips on how to make this the LAST floor we install for a very long time? We are first time homeowners and novices at all things DIY.

Thanks!

Reply

Roger

Hi Pat,

Grout line size depends on the tile consistency. 1/8″ is doable, but you need to take your time with it. If you use a good membrane beneath your tile, like ditra, if it ever floods again the floor won’t be affected by it.

Reply

Pat

Hi again, Roger.
You brought up the membrane; I had assumed that in our situation it would be better to use none. Here’s my thinking: the less there is under that tile the less chance there is for moisture (and possibly mold) to become trapped anywhere if we ever have groundwater issues again. So my intention was to install the tile directly over the concrete floor (my bro-in-law, a young carpenter/contractor will be doing the actual installation). But you think we should definitely use the membrane? That wouldn’t increase the chances of water getting trapped in the layers below the tile?

Thanks again for your help!
Pat

Reply

Roger

Absolutely you need a membrane. It guarantees that any water inside the shower makes it’s way into the drain where it belongs.

Reply

Pat

Sorry, I may not have been clear; it’s not a shower, just a floor in a raised-ranch basement. A floor which tends to flood occasionally when the water table rises (during Noah-esque spring rainy seasons).

Reply

Roger

Oh. :D In that case you can go directly to the concrete. Sorry, I’m in shower mode right now. :D

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Pat

Thank you! :wink:

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Julie

Forgot to mention that the grout appears to get wet only sometimes when the shower is running, but not always. It also appears wet when the shower has not been running.

Reply

Roger

Same answer. :D

Reply

Julie

We have ceramic tile in our shower and on the bathroom floor. Water is seeping through the grout on the floor tiles just outside of the shower pan. What could be causing this?

Reply

Roger

Hi Julie,

An improperly waterproofed shower floor.

Reply

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