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Waterproofing Membrane: Can You Tile Over It?

Tiles, as well as the grout used to join, them aren’t waterproof. So, installing tiles in a moisture-prone area leaves them susceptible to moisture penetration. Waterproofing the substrate is a great way to prevent water from damaging the tile and your structure. 

If you would like to install a waterproofing membrane underneath your tiles but do not know how to go about it, here’s a guide to help you through. I provide information on how you can go about tiling over a waterproofing membrane and what to look out for when selecting a waterproofing membrane. 


It is advisable to install waterproofing membranes underneath tiles, particularly in areas of high moisture exposure, like bathrooms. Both liquid and sheet waterproofing membranes are appropriate for use beneath tiles. Tiles should only be laid once the waterproofing membrane is completely dried.

Waterproofing Membrane Is Often Used Beneath Tiles

It is commonplace to install waterproofing membranes underneath tiles, especially in moisture-prone areas like washrooms. This is because tiles and grout in these areas are at risk of water penetration. If this happens, it can cause the tile to loosen up, encourage the growth of mold, and can lead to structural damage over time.

A waterproofing membrane prevents this from happening by creating a protective barrier between the tile and the substrate. This is why it is recommended that you apply a waterproofing membrane before tiling over any area that might be exposed to moisture. 

Types of Waterproofing Membranes

The type of waterproofing you use would depend on factors like the location, budget, and skill of the installer. There are two types of waterproofing membranes to choose from.

  • Liquid waterproofing membrane
  • Sheet waterproofing membrane

Both types of waterproofing membranes serve the same purpose. They also have their unique features and benefits. If you are considering cost, liquid waterproofing is the cheaper option. 

Sheet membranes offer more durability and strength while liquid waterproofing has higher weight-bearing properties. Although it requires more expertise, sheet waterproofing is easier to install than liquid membranes. 

You could also use a tile backer board (amazon link) or you could combine both the liquid and sheet waterproofing membrane by installing the sheet membrane and applying the liquid membrane over it.

How Soon Can You Tile Over Waterproof Membrane?

The dry time of the waterproofing membrane is dependent on a couple of factors.

  • The type of waterproofing membrane used.
  • The weather.
  • Temperature and humidity conditions.
  • The state of the surface you intend to waterproof. Porous and cooler substrates naturally take longer to dry.
  • Number of coats used in the case of liquid membranes.
  • The location of installation. Is it indoors or outdoors? If it’s indoors, is the room well ventilated? 

As mentioned, the drying time of liquid waterproofing varies based on the number of coats used. Light layers can dry in a matter of hours but regardless of the number of coats you use, liquid waterproofing dries within 24 hours. However, it could take up to 48 hours for it to cure completely

Sheet waterproofing membranes take longer than liquid membranes and require about 24-48 hours to firmly adhere to the surface.  

Construction workers are brushing waterproofing cement on tile floors in the bathroom.

After 48 hours the waterproofing should be tile-ready, regardless of the type of waterproofing membrane you used. An exception would be if any of the factors I stated earlier prolongs the curing time. 

Will the Tiles Adhere to the Membrane?

Tiles can adhere to waterproofing membranes. In fact, they probably adhere better than paint would if you were painting over your waterproofing membrane.

To achieve this, you would have to apply thin-set mortar on the membrane before installing the tile. 

Pre-mixed thin-set might not get the job done. So, I recommend that you go for powdered mortar and do the mixing prior to application. If you use pre-mixed thin-set it might not adhere firmly to the membrane and this would result in a loose tile fitting, which might come off once the mortar dries off. 

When exposed for a while, the mortar can dry out. So, depending on the size of the area you intend to tile, it’s best to mix the mortar in small quantities.

Also, do not apply thin-set over a large area at once, instead apply in bits so that it doesn’t start drying out before you install the tile. This way when you fit the tile onto the mortar, it would bond firmly with the substrate. 

How to Tile Over Waterproofing Membrane

For tiles to adhere to waterproofing, the membrane must be properly installed. 

Installing tiles over waterproofing membranes is quite similar to installing them over regular substrates. 

You will need the following items to tile over a waterproofing membrane. 

ItemAmazon link
Powdered thin-set View
Notched trowelView
Epoxy groutView
Grout floatView
BucketView
Mixing paddleView
Rubber malletView
Tile cutterView

Steps:

  1. Wait until the waterproofing membrane is completely dry before proceeding to tile.
  2. Mix powdered thin-set mortar in small batches and apply on the surface. While mixing the mortar, gradually add cool water to the powdered mortar and mix until it reaches a peanut butter consistency. 
  3. Spread mortar evenly using a notched trowel. 
  4. Install the tile to sit over the thin-set. You might have to use something similar to a rubber mallet to tap them into place.
  5. Use epoxy grout instead of regular grout to fill the joints. Unlike regular grouts, epoxy grouts are waterproof, making them ideal for this type of application. 

Helpful tips 

  • Prime the surface before applying the waterproofing membrane. This way, the waterproofing membrane would adhere to the substrate and you wouldn’t have issues while installing the tiles. 
  • A poorly installed waterproofing membrane would affect the tile installation, so it’s best to follow the manufacturer’s information while installing the membrane. 
  • Before installing the tiles, I recommend that you perform a flood test at least 24 hours after installing the waterproofing membrane. This would help you ascertain the quality of the waterproofing. 

Good Waterproofing Membrane Options

The type of waterproofing membrane you use would be determined by factors like the type and location of the substrate. 

For floor installations, I recommend that you go for a waterproofing membrane with de-coupling properties. Their flexible composition would prevent cracks from occurring.

Worker is painting by brush with green colored waterproof finish material the bathroom floor in apartment is inder construction, remodeling, renovation, overhaul, extension, restoration and

I recommend the Schluter Kerdi 108 Sq. Ft. (amazon link) if you intend to go for a sheet waterproofing membrane. It’s made from polyethylene, which is a choice material for waterproofing underneath tiles. The flexible membrane is impact resistant and it can prevent cracks from occurring, making it ideal for a variety of locations. 

One downside of the Schluter Kerdi waterproofing membrane is its high cost. Also, the membrane might not adhere firmly to every substrate. 

A great liquid waterproofing membrane is the Laticrete Hydro Barrier (amazon link). The waterproofing membrane can be installed both indoors and outdoors. It can also be used on both vertical and horizontal surfaces. The waterproofing membrane offers load-bearing properties and provides anti-fracture protection. 

LATICRETE HYDRO BAN Waterproofing/Crack Isolation Membrane Mini Unit 1 Gallon Pail

RedGard (amazon link) is another good option for liquid waterproofing. People often use it to seal the areas around bathtubs and to waterproof drywall.

However, you’d have the be careful while applying it because it is quite thin and could spill off during application.  

Sources

https://www.expressflooring.com/blog/articles/Water-Damage-to-Tile-Flooring-How-It-Can-Be-Prevented-Quick-Tips#

https://plidek.com/waterproofing-under-tile-why-its-important-and-why-its-commonly-overlooked/

https://www.no1roofing.com.au/waterproofing-membranes/

https://cdn.laticrete.com/~/media/australia/product-documents/tds/tds-1169-1117.ashx?

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