Liquid Waterproofing And Vapor Barriers For Tile Showers

By Robert Robillard on Bathrooms

Waterproofing membranes vs Vapor barriersLiquid Surface Waterproofing for Tile Showers

There are many acceptable methods to construct a quality tile shower, all of them involve different proprietary products and methods.   This article touches on the pros and cons, vapor barriers and waterproofing products.

When folks decide to remodel a shower they usually get excited on the aesthetic aspects such as tile style and color, fixtures and glass door styles.  What they don’t think about is making the shower waterproof or how they will deal with water vapor and all the other hidden details needed to ensure a long lasting and quality job.

Water vapor . . .  Whats that?IMG_0178

Water vapor is water in a gas form.  In a shower situation it’s most definitely steam.  Steam stays in a gas form until it cools down or hits a barrier such as a shower door, tile, ceiling or mirror.

Water vapor that gets behind walls or travels up throught light fixtures or HVAC grilles into an attic will turn back into water when it cools off.

Over time, this will present itself as unhealthy mold and rot.

One very important feature to any shower is a ventilation fan with a timer switch.  This ventilation fan should be sized properly to the size of the bathroom and installed to vent to the outside of the house.  there is a right and wrong way to vent a bathroom fan:  Bathroom venting options

Waterproofing Does Not Stop Water VaporIMG_0208

This is a tough concept to grasp;  waterproofing seals a surface so water doesn’t pass through it but it does not always stop water vapor from passing through.

Waterproofing a shower stops water in liquid form and vapor barriers stop water in gas (steam) form.

In the case of water vapor you will want to consider installing a vapor barrier.  Basically any material rated at less than 1 perm is considered a vapor barrier / retarder.

Examples of different wall coating products and their perm ratings:

  • 6 mil plastic: 0.3 perms
  • 15 pound tar paper: 5 perms
  • Laticrete Hydroban liquid waterproofing: 1.247 perms (2 coats, each 15-22 mils thick)
  • Schluter Kerdi Waterproofing fabric: 0.75 perms
  • Schluter Kerdi-board 1/2″: 0.48 perms
  • Noble Wall Seal sheet membrane: 0.22 perms

It’s essential to take into account all forms of moisture when constructing a shower.   If your planning a steam shower waterproofing alone is not enough.

 Seal Air Leaks

Any shower being remodeled should also have all fixtures and penetrations in the walls sealed with foam.     Insulation itself does not stop the air leaks – you need to stop air leaks in order to let the insulation do its job. Blackened insulation is always a good clue that air is leaking in the area.

The following article was used as research for this post:

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About the author

Robert Robillard

Robert Robillard

Carpenter / Remodeler / Editor / Writer / Video Talent

Robert Robillard is a remodeler, general contractor, and principal of a carpentry and renovation business located in Concord, Massachusetts. He also writes the "Ask the Carpenter" advice column in the Boston Globe, and serves as the Editor of Tool Box Buzz and founding editor of A Concord Carpenter . Rob is in charge of our Tool and Product Review - Tool and Product Review - Video Channel, , where we post all of our tool reviews and video tutorials. Rob enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the remodeling industry. The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob <a href=""

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