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How to Waterproof a Shower

3 Awesome Methods

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Waterproof a Shower

Question:

What is the best way to waterproof a shower or bathtub before tiling?

This is one of the most highly debated topics on bathroom remodeling.

Today, I’m tackling it head on!!

We’re going to discuss 3 different methods…

…all of which are awesome.

If you’re planning to remodel your bathroom you should check this out.

Let’s do it,

Getting Started

What’s the one thing homeowners hate in their bathroom?

Hint: it’s something you can eat yet probably won’t.

MOLD

Hey, cheese is a form of mold…I think.

Before you start a tiled shower or tub you need to install the right wall.

One that will be 100% waterproof and support the weight of tile.

I’m going to cut to the chase and tell the 3 methods we like

  1. Cement Board with liquid or sheet waterproofing membrane
  2. Schluter KERDI-BOARD
  3. Wedi Building Panels

Let’s discuss each one and at the end I have a cool surprise.

 

How to Waterproof a Shower with Cement Board

Should you lay cement board on the tub deck or above the tub lip?

This is a common question.

Our suggestion is to hang cement board above the tub lip.

Here’s why:

Your tile will look better.

If you position the cement board over the tub lip, it will bow out.

When you hang the tile it will also bow out.

NOT GOOD.

Lay scrap pieces of wood on the tub deck to support the cement board.

The wood should help raise the cement board above the tub lip.

Tub Lip

Then mark the niche location on the cement board.

Niche Location

Cut cement board with either an angle grinder, carbide tipped knife, or utility knife.

If you use an angle grinder we recommend equipping it with a tile blade like this one (this is an Amazon affiliate link..so thanks if you use it).

Angle Grinder

Furthermore, when hanging cement board use only alkali resistant screws.

Other screws will corrode, especially drywall screws.

Position screws 1 inch from the edges and every 8-10 inches in the field of the board

Screw Location

Also, make the cement board flush, or as much as possible, to the ceiling.

Cement Board Ceilng

How do you cut tub spout and mixing valve holes?

Steve uses a paddle bit to cut a hole for the tub spout and shower head arm.

Cement Board Tub Spout

And a 3 inch hole saw for the mixing valve.

Cement Board Mixing Valve

Finally, what’s the ONE mistake some homeowners make with cement board?

NOT waterproofing it.

I’ve said this in other tutorials:

Cement board itself is not waterproof.

You need to apply a liquid or sheet membrane over it.

In today’s video we use Ardex 8+9.

Ardex 89

Mix it up and paint it onto the cement board.

Applying Ardex 89

Today’s video gives you a brief overview of Ardex 8+9.

We also have a complete tutorial showing step-by-step how to apply it.

Cement board is cost effective, there’s no doubt.

But you need to budget for a waterproofing membrane.

This will add $100-$200 to the total cost.

Also, cement board is heavy and a bit cumbersome to cut.

PLUS dusty…which is always a pain to clean up.

What are your options if you don’t want to use cement board?

 

Schluter KERDI-BOARD…Light AND Easy

How much can you shoulder press?

Seriously,

You need to know before installing cement board.

Or at least I feel this way.

One 3 x 5 foot cement board panel weighs about 25lbs.

I weighed it while standing on my scale…now that’s a site!

Schluter KERDI-BOARD on the other hand weighs less than 4lbs for a 48″ x 60″ sheet.

This means anyone can man handle a KERDI-BOARD sheet.

First things first, take a level and make sure your studs are plumb and level.

Level

Foam boards like KERDI-BOARD need a plumb stud wall.

Otherwise they will bow out and this, as I said earlier, will affect your tile job.

This should be done for for cement board as well.

Also, we suggest mounting the KERDI-BOARD above the tub lip.

KERDI Tub Lip

Install KERDI-BOARD using Schluter’s screws and washers.

If you’re thinking of getting a niche, Schluter makes great prefabricated ones.

We show you how to install it in the video…it’s way easier than building one.

KERDI Niche

We like making KERDI-BOARDs flush with the ceiling.

KERDI Ceiling

Holes can be cut using a utility knife or holes saws

KERDI Holes

All screws, washers, and seams need to be covered with Schluter KERDI-BAND.

The first step is to mix up unmodified thin-set to a pancake consistency

Pancake Thinset

Then embed KERDI-BAND

Embed KERDI BAND

Schluter has special recommendations for the tub to KERDI-BOARD joint.

Fill that in with KERDI-FIX and apply unmodified thinset to the KERDI-BOARD.

Then embed your KERDI-BAND in both and smooth it out.

This ensures a waterproof seal between the tub and KERDI-BOARD.

KERDI Tub to BOARD

KERDI-BOARD is great because it’s light and easy to install.

If you think it’s simpler than cement board you’re right.

 

Putting It All Together

The third method for waterproofing a shower is the easiest of the three.

It’s called wedi.

I bet you’ll love it

Check out the video for the scoop on wedi and to learn the other two methods.

I left a blooper at the end…

…you’ll see what really happens when making a video about showers

 

What’s Next

Our tutorials on wedi and KERDI-BOARD are invaluable if you want to use these backer boards.

Grab our free guide if you’re doing a DIY bathroom remodel – it shares how to remodel a bathroom in 10 days or less

Send Me The Guide

 

Thanks as always for reading, watching, and being part of our awesome community.

Ask your questions below and we’d be happy to help.

Cheers,

Jeff Patterson

 

 

 

 

P.S. Our online store has great supplies for homeowners doing a bathroom remodel. You’ll find shower systems, tiling tools, and more.

31 Comments
  1. Susan says:

    I think I would use the Kerdi. Reason? Because there are lines on it for easy and straight cutting. I also like the tape/band use over the seams and fasteners.

    1. KERDI is a great options Susan.

      The boards come in all different dimensions, too.

      You can get 1/2 inch, 1 inch, etc.

      Keep that in mind if you have old walls made from plaster, it makes matching the transition so much easier than using cement board…which you can only find in 1/2 inch

  2. Nancy Tuttle says:

    K.I.S.S. Kerdi-Board gets my vote because it appears to have less steps, tools, and materials involved to get the job done, ergo less mishaps and frustrations for a female going solo on a project.

    1. KISS is a great mantra to live by.

      You’re right Nancy, I think Schluter has thought of ever possible mishap that could happen and accounted for it.

      PLUS, their tech support is awesome…they always answer and always have great answers.

  3. Norman Levig says:

    If I was as skilled as you, I would use method 1, otherwise I would use method 2 and even that one would be a big challenge for me.

    1. KERDI and Wedi are super straight forward, I bet you could do it Norman.

      Once you plan the tub or shower surround, putting it together isn’t all that bad.

      Plus, if you get stuck you know where to ask questions 😀

  4. Bob Sanchez says:

    You forgot mudding the walls as an option. I gave been doing this for 25+ yrs and it is still the best way to plumb, square and waterproof any shower

    1. Thanks Bob for your tip, I can totally understand your position.

      For a DIYer it would be tough to get plumb walls with mudding. That’s why I recommend shimming them or sistering then attaching KERDI, Wedi or cement board.

      Plus, the KERDI and Wedi provide a great waterproofed wall.

  5. Victor Ramirez says:

    Cement boards looks like the most durable? In a case where any of the three options are doabl, which one would you recommend the most?
    Regards.

    1. Personally I love KERDI or Wedi. They’re a bit more expensive but easier to install and no extra waterproofing is needed on the surface, unlike with cement board.

  6. Noe Villegas says:

    I live in the Chicago area. I have used cement board, Kerdi and Hardi-backer board. With preference going to Kerdi; but I have not seen Wedi brand boards anywhere.

    1. Wedi is pretty awesome, it’s similar to KERDI but slightly different. You can use their sealant for all the corners, seams, and screws. Plus, after 2 hours you can start to tile. So if you’re a contractor this is a HUGE upside…time.

  7. Jeff says:

    Another option you should be aware of is Finpan’s Propanel. It is used just like any other inherently waterproof foam core board like Wedi, etc. It isn’t quite as stiff as Wedi so depending on your install you may wish to use extra blocking behind it – we simply spaced the studs at 12″ instead of 16″. This worked out very well for a very large format custom travertine shower with 9′ ceilings and angled walls.

    It was easy to install and waterproof – all by myself with no helper. We are about to build out another custom travertine shower and will absolutely be using this again. If one doesn’t mind

    1. I’ll have to check that out Jeff, what’s the price for the Propanel? Wondering if it’s comparable to KERDI and Wedi. I do like the stiffness of the KERDI and Wedi, in terms of a foam board. Wedi is a bit stiffer than the KERDI overall but that doesn’t affect the performance. Foam boards are easier to use for sure, cement board was a great option but I’d stick with the foam all day.

  8. waykno says:

    I would probably go Kerdi. I can do a few things but Murphy’s Law always seems to be present for me:-)

    1. Murphy has been all over me this week…understand where you’re coming from :/

      KERDI is awesome, I don’t think cement board will ever be in my future again…unless Schluter and Wedi go belly up

  9. John Provenzale says:

    Never used anything but cement board for tile or stone. Is foam board same for heavy stone walls?

    1. John Provenzale says:

      This is John (again). In the question above, I meant to type: Is foam board SAFE for heavy natural stone walls? (It may be for tile but stone is much heavier)

  10. Brian says:

    I am remodeling a bathroom. It has plastic behind the cement board. Can I also use Red Gard on top of the cement board or would that trap moisture? Also, should the gap between the cement board and lip of the tub be caulked with silicone? If so, should there be weep holes in it. Thanks for the help.

  11. Russ says:

    I helped a guy several times and he just put up purple sheet rock then used thin set to attach kurdi membrane over entire sheetrock with 6 inch overlap. IS THIS A GOOD PRACTICE?

  12. john says:

    The Kerdi board looks like relatively easy installation; however, not sure if it is as strong as cement board for backing of tile.

    1. It’s strong and only requires 16″ on-center stud spacing. Btw, cement board needs that spacing, too. Foam backer boards are way easier to cut and install than cement board, and they don’t need an extra liquid waterproofing. Just something to consider.

  13. Patricia Gomez says:

    Is it ok to use something like roofing tar to waterproof a shower bottom. They did it in another apartment and I do not want that method used in my apartment.

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