Tag Archives: bathroom

Step 5: Bathroom waterproofing walls

The principles behind waterproofing some of the walls in the bathroom are the same as those for waterproofing the bathroom floor. Rather than repeating them, I would like to direct you to the recent post: Bathroom waterproofing.

That said, there are a couple of subtleties that are worthwhile pointing out.

A good strategy to manage accidental and incidental water spills in your bathroom is to use water resistant materials and waterproofing in all wet areas. Here is what I said about wet areas earlier: “Think of wet areas as everything that is tiled.”

The entire bathroom floor is part of the wet area. It will all be tiled and has a waterproofing membrane. I used a bathtub analogy earlier: “Because of the amount of water a bathroom handles, we should treat it like a big bathtub”.

Waterproofing the floor makes for a very shallow bathtub, and doesn’t address the other vertical surfaces (walls) in the various wet areas of the bathroom. We need to raise the rim of our tub. But what are those other wet areas?

Two out of the three water sources in the bathroom are the sink and the toilet.

The walls surrounding both the sink and toilet are part of the wet area.

They should be furnished with cement board and waterproofing up to a safe splash height of around 44 to 48 inches.

The third water source is our barrier free – or – walk-in shower. This area will not just receive incidental or accidental spills–it will be exposed to water on a daily basis.

The walls surrounding the walk-in shower on three sides are furnished with cement board and will receive waterproofing.

Even though we plan to put a cabinet beside the shower, and protect it with a shower curtain, we decided to extend the waterproofing behind the cabinet just in case it may be removed sometime in the future.

The one lesson I took away from this exercise is that it is a excellent idea to have a time lapse camera going so you get to learn how your wife really feels about waterproofing the bathroom with you! 😉

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Step 4: Bathroom taping and mudding

The wall board in the bathroom is up and ready for taping and mudding. But it isn’t drywall or gypsum board. It is water-resistant cement board.

Using the typical paper tape and mud used in drywall applications won’t work. Neither of these are water resistant and as such are unsuitable for wet areas. Instead, the use of an alkaline-resistant mesh tape and thinset mortar is recommended. Both are water resistant, compatible with the cement board, and add to the durability of the system.

Why bother to use mesh tape and thinset to mud all the cement board joints if everything gets tiled anyway?

The taping and mudding bonds the individual cement boards together to create a monolithic face. In other words, the mesh tape and thinset help to cut down on movement between the boards, which is crucial to prevent cracking in the grout lines and wall tiles.

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Step 3: Bathroom waterproofing

Because of the amount of water a bathroom handles, we should treat it like a big bathtub. In our case that bathtub has two drains. But that bathtub should also hold water – or more precisely, be waterproof.

The point here isn’t that we plan to fill our bathroom with several inches of water to go for a swim, but that we acknowledge that there will be incidental and accidental spills that could lead to water damage and durability issues if not managed properly.

I am a fan of “properly” and “proactively!” So our entire bathroom floor will be lined with a waterproofing membrane that we fold up on the walls by about four inches. It basically could be a shallow bathtub (except for the door, of course).

If we do our job right, no water from incidental or accidental spills or the walk-in shower would get past the waterproofing membrane and into the concrete floor and framing beyond.

But don’t relax yet, because there is a lot more to it! How many bathrooms do you recall where you saw cracked grout lines in the floor, or even cracked floor tiles?

A fact that comes with framed structures (in our case our floor joists) is that they move due to thermal expansion and contraction. And yes, we poured a concrete floor, but that won’t put a stop to material movement for a couple of reasons. First, we integrated radiant heat into the floor, which will lead to thermal expansion and contraction. Second, the concrete cover over the floor joists is thinner than elsewhere.

All this basically guarantees that there will be some level of cracking. It will probably be very minor, but enough to migrate up to grout lines or even floor tiles.

The waterproofing membrane we selected (NobleSeal TS) provides crack isolation. Small and hairline cracks in the concrete floor should not pass the membrane, and thus it prevents crack migration into the thinset tiled floor above.

Not only are the benefits aesthetic (i.e. no cracks in the tiled floor), but also maintenance related (i.e. no cracked grout lines to repair). And last but not least, there is the added benefit of durability. With an intact first layer of defense (tiles and grout) water is less likely to get down to the second line of defense, the water proofing.

In case you are wondering if this is all worth the effort, just talk to some contractors who have experience remodeling 100+ year old buildings. They possibly have some good horror stories on what even small water damage can do to a building over time.

Before I move on to step three, let me extend our sincere thanks to our friend Rubani who helped me wrestle the waterproofing membrane.

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Step 2: Bathroom drain flashing

All wet rooms, and this includes bathrooms, should have a floor drain. There are always spills, splashes, the sweating toilet tank, and maybe the occasionally overflowing sink. The floor drain should capture and manage that unwanted water before it can do any major damage and affect durability of other building materials.

We decided on two floor drains: one servicing the barrier-free, walk-in shower, and the second one (the main floor drain) catching any unwanted and occasional spills. The concrete floors are poured and sloped towards the two floor drains. The next task was to waterproof the floor drains. This was sort of a big deal, as the shower drain will and the main floor drain may receive a steady flow of water that should just go down the drain and nowhere else!

The good news was that I didn’t need to reinvent the wheel. There are various drain flashing options available that would do the job. We used the Schluter product in the basement bathroom and the Nobel product on the 1st and 2nd floor.

As you can see in the time lapse above, I had to adjust the concrete floor around the drain because I didn’t have the drain flashing tool available when I poured the concrete floors.

The drain flashing tool is a simple pre-cut piece of foam board that pre-forms the concrete floor to perfectly fit the actual flashing. If you use the Nobel product, plan ahead and have the flashing tool handy when you pour the concrete floor (the tool comes with the drain flashing). It will save you some time and make the process easier.

Last but not least, here’s a summary video of the installation:

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Step 1: Bathroom wall board

I have mentioned what damage water can do to building materials. Using appropriate building materials (i.e. water resistant materials) is critical when it comes to durability. And despite the word on the street, or the marketing material, or what your contractor may tell you, the famous ‘green board’ has no place in the wet areas of your bathroom.

Think of wet areas as everything that is tiled. Green board is still a gypsum core with paper backing on both sides. And paper and water don’t mix. The board eventually could get compromised and grow mold, leading subsequently to indoor air quality (IAQ) issues.

I would recommend paying a few bucks extra and investing in cement board, which definitely is water resistant. How do I know? Well, the experts say so, and there is anecdotal evidence.

I have a little piece that has been sitting for a number of years in the garden, and it is still holding up just fine. Try that with a piece of green board!

Cement board was again our choice for the bathroom wet areas. In our case that was the shower stall, the area behind the toilet, and around that lavatory.

The shower stall will receive cement board almost reaching up to the ceiling. In the area surrounding the toilet and lavatory we limited the cement board to four feet above the floor. This way all wall areas that would intentionally or could accidentally receive water have a paper free, cement based and water resistant wall board. I also highly recommend to use special, alkaline resistant screws to attach the cement board to the framing.

The cement board will receive additional waterproofing and tiles, which should give us the reasonable amount of durability we are seeking.

More about the waterproofing and tiles in the coming posts.

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