Is Tile Really Waterproof?

Is Tile Really Waterproof?


The short answer is no, but the longer answer is, well, still no. And while we’re at it, let’s dash all hope that grout is waterproof. It is not. When it comes to tiling jobs, preparation is key in preventing water damage. 


Tile adds so much character, style, and attitude to a room it’s difficult NOT to use it. Let’s start by looking at three types of tile and how they might work in a shower. Ceramic tiles are referred to as “water-resistant” since they’re not damaged by water but they can absorb water. Don’t use them in a shower project. Porcelain tiles are considered “waterproof” because water does not appear to absorb into the top of the tile even though it can. Glass is the only tile that is 100% waterproof. Still you can run into problems with any type of tile if your substrate is not properly waterproofed.


When evaluating the type of tile you want to use, you need to know its moisture absorption rate, especially if you’ll be using it in places where there will be a lot of water, like a shower. Let’s take a quick look at the four moisture absorption ratings:


  • Non-vitreous (Low density) – Tile with water absorption of more than 7.0%
  • Semi-vitreous (Medium density) – Tile with water absorption between 3.0% and 7.0%. Ceramic tile is often in this category. 
  • Vitreous (High Density) – Tile with water absorption of more than 0.5%, but not more than 3.0%
  • Impervious (Extremely dense) – Tile with water absorption of 0.5% or less. Porcelain tile is often rated as impervious or vitreous. And of course glass tile with its 0.0% absorption rate falls into the impervious category.


Tile, stone, and grout all retain some water, and the density of the tile affects how much. So before you rush out to the nearest home improvement store, think about how much water the tile will be exposed to and if the tile will be outdoors. An outdoor location is only an issue if you get major freezing temperatures in the winter – think Michigan, Minnesota, North Dakota, Maine, and Canada.


The durability of your tile will be only as good as what’s beneath it (a.k.a. the substrate). And here is where we need to stress that you should allow a professional to do this. You can surreptitiously check out the installer as he/she is doing the work, you know just to make sure they know what they’re doing. If your tile professional tries to mount your tile directly on drywall, then you know they’re doing it wrong. Be gone, rank amateur!


The reason we’re focusing on the shower here is because it is the place that dispenses the largest amount of water. Once water soaks through tile and grout, it can seep through to the studs causing the wood to swell. Just one simple and quick way to give yourself a huge headache and an even larger repair bill.


So it’s well worth the money to have the job done right the first time. Hire a professional to install your tile, especially in the shower since tile and grout are not waterproof. Ask neighbors for referrals or look up local businesses in your area through Home Advisor, Angie’s List, and others. The reviews should help you find a competent installer.


Let’s look at several of the correct practices that will assure you that your new tiled shower is in fact waterproof.

Traditional shower construction – Water in water out

A traditional water in water out shower is constructed from concrete and cement backer board. the cement backer board would then need to be painted with a waterproofing membrane like Ardex 8+9 or redguard. The problem we have found with this method is that after all that labor and materials you were better off buying a better product from the start. The main issue with a traditional system is the concrete basin used for the floor. This concrete acts as a large sponge ready to soak up any available water. Trapped in the water is soap scum and organic material that can decay over time and begin to emit an odor. In our opinion with the new products on the market and the small difference in cost vs labor it is simply a disservice to the homeowner to install a traditional water in water out shower. 

Foam shower systems – Fully waterproof showers

A more updated shower system would be built with all foam products. For this reason we suggest using a product like Wedi or Schluter. The Wedi system is a closed cell foam board with cementitious coating making it the ideal surface for tile installation. The closed cell foam system is antimicrobial and doesn’t allow any water to pass threw the substrate making a complete barrier from the  framing of your home. The wedi system also is joined at the seams with a unique sealant that makes the entire shower one piece when finished.  

Perform a Flood Test 

If your shower will leak, it’s best to find out before it’s tiled. To perform a flood test, your installer should plug the drain and fill the shower with water just below the top of the curb. If there are no leaks, you can rest assured, knowing your shower has been properly waterproofed before you hand over that last payment.


Never Use Tile Mastic Adhesive in a Shower 

Or anywhere else for that matter. Tile mastic is a premixed organic adhesive. Don’t use it in wet areas, on cement or fiber cement board, floors, with glass tile, or natural stone. Basically never use it anywhere – ever. Stop it right now.

Know your glass installer

All to often in our findings is an unknowing glass installer drilling a few holes threw your curb into the substrate and penetrating the waterproof barrier. With the wedi system this is not a problem because of the pure foam curb but, with other systems we find contractors using 2x4s for the curb and wrapping it with a rubber liner or painted redguard. This costly mistake drives the nail in the coffin for a leak to begin.  A way we like to combat this is by not drilling a hole to begin with. With new products on the market like Ardex CA20-p adhesive and sealant shower door hardware can be attached directly to the face of the tile without the need for fasteners.

In conclusion, when tiling a shower, be sure to hire a professional. It takes a lot of experience to properly install tile. There are several steps for preparation and waterproofing that cannot be skipped. Now that you have some of the basic waterproofing facts, do yourself a favor and hire a competent tile installer. You’ll be able to ask the right questions and understand the process as it goes along. And when it’s all said and done, you’ll have a sparkling new waterproof shower!









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Andrew D

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