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.

Previous post:

Next post:


Dear Clay! We have a balcony off our bedroom, which two decades ago, we had a contractor tile and grout its surface. We thought that might be part of a solution to occasional dampness getting into the room below. That seemed to work.
Recently, another contractor in our home, pulled up one of those tiles and showed us it was moist underneath.
Can we brush on a clear sealant of some type on top of the tiles and grount to prevent moisture damage from occurring, or do we have to pull up all the tiles and begin again? Since the area is rarely used, we want the easiest, most affordable solution. Thanks!



My contractor removed all down to studs, installed DurRock on walls, painted corners with RedGard. Thhen installed 12×24 wall tiles by placing a cup full of thin set on each end of tiles and stuck them to the walls. This leaves a cavity around perimeter of each tile. No moisture barrier on walls.
Tiles are porcelain, smooth surface. Potential moisture problems?



I just removed a 40 year old shower. The tiles word directly installed over green board sheetrock. This would never be done today and yet virtually no water at all and certainly no damage in over 40 years. Things have to be done right but people are obsessed today and there are a lot of unnecessary expensive products designed to address problems that don’t exist.



We used rocks (pebbles)glued on mesh for part of the wall in the shower. Some of the rocks are touching and we cannot get grout in between that part. We are going to seal it, but want to know if water will get in between the parts of the rock that are touching? Do we need to grind a space to get grout in there?
Thank you,




I have vinyl square kitchen flooring that needs to replaced because corners are poking up. The squares were placed directly on the subfloor. I want replace the squares with a SHEET of vinyl flooring. Should I use a waterproof underlayment between the subfloor and the vinyl sheet flooring? If so, what kind? Thank you.


Maria Bella Jamison

can you give me a good tiles in our bathroom, my new renovated tiles in our bathroom was colored dark brown and suddenly it becomes faded out and had watermarks. please help me buy a good tiles or is it good a tiles that are glossy look. thanks…..



Hello , I had my bathroom remodeled and now the tiles inside the showers is leaking down into my kitchen what can I do to fix this problem



Hi Donald,

Apparently your shower was not properly waterproofed. I would call back whomever remodeled it and have it properly replaced.


Pat keoghan

The best I have read in a long time. :lol: :-D :-D


clive carrinton

I have an outside patio in the south France. What is the best solution to water proof the cement base before tiling it



Hi Roger,

I am wanting to tile my bathtub surround with travertine tile; however, according to Lowes, this tile is Vitreous. Can I still use it as a surround? Or should I pick a different tile to use? I know you have said a sealer will only protect against stains, but if I properly waterproofed the walls behind the tile then used a sealer on the tile, will it be ok?

Thanks for your help!



Hi Nicole,

Someone at lowes get a word of the day calendar or what? :D Yes, provided your substrate is properly waterproofed it will be just fine. You don’t even need the sealer if you don’t want it.



Hi there,
I’m looking at tiling the down stairs part of my house.
The floors at the moment are concrete, I know I’ll have to water proof the bathroom but I’m looking at tiling the rest of the area (to turn into a granny flat)
I know they aren’t naturally waterproof so I was wondering will they lift if a bit of flood water comes in over top of the area? Weather it be waterproofed or not?



Hi Nikitta,

Water isn’t going to affect tiles that are properly installed with thinset. It doesn’t have to all be waterproofed.



Hello Roger,

I am renovating my bathroom.
Due to my shower leaking through the common wall to our bedroom and the wife wanting the bathroom updated.

I’m in Perth Western Australia and the house is brick construction all internal walls are single fast wall bricks with concrete floors.

I have removed everything from the bathroom.
Removing tiles from the wall, removed cement screed and tiles from floor.

I have noticed there was no damp course or waterproofing behind the tiles or over the hob in the shower.

We had the house built in 1989 (local builder) so its lasted for a long time before leaking.

When I ripped or jack hammered the wall tiles off the shower wall it removed the cement render. I had a tradie in to re render the wall yesterday.

I know the tradie (cement render-er) did not mix any damp proofing material in with the cement render. (I now know he should have reading your previous comments).

Q1. Do I now paint or apply a water proofing membrane to the walls and floor to waterproof the area before getting a Tiler in to lay the tiles.

Q2. Can I paint or apply water proofing to cement render.

The new HOB for the shower will be installed or done by the tiler, as the hob is placed in situ so the floor tiles are easier to lay or more importantly the Tiles fit better so there isn’t any small pieces of tiles.

Q3. Should I just leave it and let the tiler waterproof the entire Shower area.

I would prefer to email you a couple of photos to explain it better, but there doesn’t seem to be that capability here.





Hi Clay,

It would likely be best to let the tiler waterproof it, but you can apply a topical waterproofing like redgard, hydroban or kerdi.


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)