Just look at you! Sitting there with a hole in the wall of your shower. What are we gonna do with you? If you do not happen to be sitting there with a hole in the shower of your wall read How to Build a Niche for your Shower – Part 1 and join all the cool kids. We’ll wait…

There, now you’re one of the cool kids. Now take your beer Pepsi off that niche shelf so we can waterproof it. You have a couple of different methods with which you can accomplish this.

Liquid Waterproofing Membranes

These products are usually readily available and fairly simple to use. Products such as Custom’s Redgard and Laticrete’s 9235, Hydroban, Hydrobarrier, etc. are all a thick, paint-like product which is brushed or rolled on to your substrate to waterproof it. You should only use these products if you are using a cementious backerboard as your shower substrate, they should not be used over regular drywall.

If you do have a cementious backerboard and choose to use one of these products for waterproofing simply follow the directions with whichever product you choose. Make absolutely certain that you get enough of the product in your niche to effectively waterproof it. The specifications vary but the best way I can explain it with a general rule would be the thickness of a credit card. Two or three good coats and you should have a layer on your substrate equivalent to the thickness of a credit card – that would be the correct amount.

I use to waterproof niches this way until I started doing them with Kerdi. Unfortunately I don’t have any photos of a niche I’ve waterproofed with a liquid membrane. Just make certain you have every (literally) pinhole and corner covered very well. For the remainder of this post I will describe waterproofing your niche with…

Schluter Kerdi

Kerdi is now my preferred method of waterproofing a niche, bench, floor, wall, beer Pepsi cooler, just about everything. For those unfamiliar with Kerdi it is the orange membrane on the shower walls in all my photos.  It is a thin polyethylene sheet which is installed directly to drywall and/or deck mud as well as other substrates, to make it waterproof. It is easily cut with scissors or a razor blade and can be folded, molded around curves, etc. and is installed directly to your substrate with regular (unmodified) thinset. A very versatile product.

While there are countless ways to utilize Kerdi to make your niche waterproof I am going to walk you through the way to cut and install it using one single sheet cut to size for your niche. I say type there are countless ways because there is really no *particular* way which Kerdi must be installed. As long as every piece is overlapped 2″ your substrate will be waterproof – no matter how many pieces you use. I just prefer a single piece cut to whatever size I need for the particular niche.

Measurement diagram for Kerdi nicheSo what size do you need for your niche? Here’s how to figure it out. The badly created diagram to the right explains it better than I can with words, you can click on it for a full-size version.

It is basically the width of your niche plus the depth (twice)  plus 2″ (twice). See? I told you the diagram was easier.

For my 13 x 13 x 3 niche the measurement for the piece of Kerdi is 23 x 23. That is 13 + 3 + 3 + 2 + 2 = 23. Width + depth + depth + 2 + 2 = width of kerdi. The two inches (twice) is for the overlap on the outside of the niche. Remember I said kerdi needs to be overlapped 2″ – that’s what that is. 2″ on each side of the niche.

For a square niche both measurements will be the same. If you are creating a rectangular niche the width and height measurements will be different – they need to be figured differently.

Kerdi marked for shower niche

Photo 1

So here is my piece of kerdi for the niche. (Photo 1) You can see the measurements marked out. Take a ball-point pen or pencil and mark the measurement lines on the piece of kerdi.

At the bottom right of this piece I have marked the two partial cuts you need to make in every corner as well as the small square piece to remove. (Hold on to that piece – don’t throw it away)

Cutting each corner in this manner will allow you to fold the kerdi into your niche correctly and have an exact fit. Make sure you do not cut the lines too far, it’s always better to cut them a bit short and fine-tune it later.

Kerdi cut for niche

Photo 2 - Kerdi cut for niche

In photo 2 the kerdi is cut to fit into the niche. After you get it all cut you should place it into your niche to ensure that it fits correctly. Just take the piece of kerdi and place it into your niche like photo 3 here:

Dry-fitting the kerdi

Photo 3 - Dry-fitting the kerdi

Take the inside corners – the ones that go into the back corners of your niche, and push them tightly into each corner. If measured correctly the corner marks on the inside square should fit perfectly. Wrap the top and bottom flaps over the niche and onto the wall outside.

The side flaps then get smoothed onto the sides and all the strange corner pieces you cut out will fold over the top and bottom flaps and outside to the wall with a 2″ overlap. If fitted properly it should look like photo 4 here:

Correctly cut and fitted kerdi for niche

Photo 4 - Correctly cut and fitted

At this point make any minor adjustments in the cuts or remove any excess you may have and make all the folds over all the corners to make sure they fit tightly.

After you ensure that the fit is correct its time to actually install it. Make sure you are comfortable with the way it fits and how it folds into there. Remove it and replace it a couple of times until you are sure you know how to do it. Once you start playing with the thinset it gets really messy very quickly if you need to make adjustments. I became a tile guy because I like playing in the mud – you may not.

Pull the piece out of there and comb your thinset into every corner and part of the niche and about 2 1/2″ around the outside of the opening. You need to make sure you get every little bit covered. There must be full coverage behind the kerdi to make everything waterproof.

Combing thinset into and around niche for kerdi

Photo 5 - Combing thinset into and around niche for kerdi

Placing the kerdi into the niche

Photo 6 - Placing the kerdi into the niche

When you go to place the kerdi into the niche you should fold in the sides as it will be placed into the wall. By folding the flaps over and in before placing the kerdi in it will help get it in the right place with a minimum of mess.

Start with the upper two corners in the back of the niche and press them in there very firmly. Make sure the line between those two corners follows the corner of the wall in the upper back of the niche. This is why you want to draw all the lines onto the kerdi – it will assist in getting the piece all lines up and in the space straight and square.

When you get those corners and the line between them pressed in firmly run your fingers down each side of the back of the niche to make sure the lines follow the niche. The lines you drew on your kerdi should follow the lines of the niche exactly.

Smooth out the entire interior of your niche starting with the center of the back wall and working outward. You need to make certain there are no air pockets behind your kerdi. Once the back wall is firmly in place start with the sides of the niche working from the back to the front wall again ensuring no air pockets remain.

Once the entire inside of the niche is smoothed down and flat start with the main flaps by using your index finger and thumb along the outside edge of the niche to get a nice, square transition around the corner like this:

Smoothing outside edges of niche

Photo 7 - Smoothing outside edges of niche

If you look closely (or click on it for a full-size view) you will notice that only the first inch or so around the outside edges are completely smoothed down. You want to get that nice and tight before worrying about the remainder of those flaps.

After you get the large, main flaps installed and smoothed out flat you can start with the inside corner flaps. Just do one or two at a time and don’t rush through these – they are the point where your overlaps create the waterproof aspects. I do the two opposite corners at a time.

Installing two of the corner flaps

Photo 8 - Installing two of the corner flaps

Finish installing the remaining flaps

Photo 9 - Finish installing the remaining flaps

You want to take considerable time and great attention to detail while installing these flaps. The tighter the seams are together where they overlap the more dependable they will be. Kerdi is made waterproof by the overlapping and attaching of the seams – the tighter the better. Get it all smoothed out and tucked in and you will have an absolutely waterproofed hole in your shower wall. That is, after all, what you are building – a hole in the wall.

Now, if you are anal retentive attentive to detail like I am there will probably be one or two spots which may concern you for one reason or another. Remember those 2″ square pieces you cut out of the corners that I told you not to throw away? There’s your patch. Just comb thinset over the spot that’ll keep you awake tonight and install the patch over it. The outside corners of your niche may be one of those areas.

See photo 9? It’s a frickin’ mess. If you aren’t making a bit of a mess you aren’t doing it correctly. Yours should be a bigger mess than mine. Don’t be afraid of it – thinset is your friend. Besides it looks better after is sets – see:

Finished waterproof shower niche


If you do it the right way you will never have to worry about leaks, standing water or any other fun problems associated with an improperly built hole in the wall. When done correctly you will end up with an absolutely waterproof niche in which to store your rubber ducky! See:

Niche for your rubber ducky

Thought I was joking, huh?

You thought I was joking about the rubber ducky, didn’t you? I wasn’t. I build showers – I like rubber duckies.

In my next post I will describe various ways you can place tile in your waterproofed niche for maximum rubber ducky storage.

{ 236 comments… add one }

Leave a Comment

  • Noel

    Hi Roger,
    Thank you for the detailed instruction on waterproofing a niche.

    What size spacing are you using for the tiles?

  • Kevin Smith

    Good info..i cant quite tell from the pictures…..the tile directly under the the niche, is the top edge flush with the bottom of the niche or slightly below? Thanks in advance.

    • Roger

      Hi Kevin,

      It’s flush.

      • Kevin Smith

        Ok, great…thanks.

  • David

    Hi Roger,
    When using cement board and liquid waterproof membrane, instead of Kerdi, how do you attach the cement board to the walls of the niche. I assume the sides, top, and bottom would be screws, but the back attaches to the sheetrock of the room on the other side of the wall. Would liquid nails or a similar product be used?
    Thanks for all your help.

    • Roger

      Hi David,

      Just use thinset. It will bond the backer to the backside of the drywall just fine.

  • Tom

    Hey Roger,

    I had a question about creating the niche using a liquid membrane and cement board as the backer. What’s the easiest way to cut out the alcove out of the cement board? I find it tends to be pretty hard to work with, and since the piece being cut out is supposed to be the backer of the niche, I figure that’s supposed to be a clean cut.

    • Roger

      Hi Tom,

      I use to use a rotozip (I say used to because I rarely use cement board any more). If you don’t have one the best is just a hell of a lot of shallow passes with a razor knife.

  • Bruce

    Do not use outside walls. The only wall I can use for a niche is a wall abutting the attic. Essentially the same as a outside wall. Being in central Texas, freezing temperatures are not much of a issue. Any tips for using that wall besides boxing it in the attic to allow insulation to be installed behind it?

    • Roger

      Hey Bruce,

      Not really, that will work just fine for your niche.

  • Wade Neely

    I find myself caught between a tile guy that I had to let go and trying to find someone to finish his poor work. I will likely remove the tile (1/3 on walls) but it’s a floated stall with a hot mop pan and I don’t want to tear that out. With your info on niches, I think I can fix and waterproof it satisfactorly. Thanks for your unselfish help for all us poor folk finding ourselves in trouble.

  • Joe Radosti

    Hello Roger,

    I’m renovating my bathroom, and I’m using 1/2″ Kerdiboard in the stall shower, which is 32″ x 36 5/8″. I also purchased the KERDI-BOARD-SN 12” x 20” niche. I have 12″ x 12″ tiles for the shower stall walls. After reading the information on your site, I’m not quite sure how to install the niche without making it look like an after thought. Can you give me some recommendations?



    • Roger

      Hi Joe,

      Yeah, take the niche back. :D If you are using 12″ tiles then line up your layout so they fall on each side of the niche with one in the middle (inside). The top and bottom cuts will look fine.

  • Bob

    Have you reviewed Trugard yet – lower cost Kerdi type option

    • Roger

      No, but there are a lot of alternative products similar to kerdi. They all work when properly installed.

  • Bob

    I am so glad I found your site.. informative and funny, all at the same time!
    two quick questions:
    1) would it work to cut twice along the 3″ lines (still taking out the small corner) and not cutting the 2″ side – that way that 2″ flap runs past the corner instead of doubling over the bottom and top, and you still have the 3″ running over the inside?
    2) after the membrane is in place and before tiling, would you recommend sealing the corners with liquid sealer (redgard) ?

    • Roger

      Hi Bob,

      1. Maybe. :D I can’t picture what you’re asking, but provided you have the proper overlap with kerdi it doesn’t matter where you do it or how many pieces you use to do it with.
      2. Sure, never hurts. I keep a 1 gallon of hydroban in the truck for such things.

  • Trevor

    Hi Roger,

    I have my niche waterproofed and ready for tile. My question is in reference to the Schluter Rondec edging. I don’t have any bullnose tile for the niche so I will be using the edging instead. I noticed that some people. Simply mitre the trim around a niche, some use the double leg inside corner and some use the inside corner with no legs. What is the preferred method of doing this given that I’m a fairly amateur tiler who’s only doing this because you’re website gave me the confidence to go ahead and give this a shot? Thanks in advance.

    • Roger

      Hi Trevor,

      The double leg inside corner is the easiest. After that the no leg, then the miter.

  • Adam

    Thanks for this writeup! Is there any benefit to using the pre-formed inside and outside corner pieces that are sold? Looks like there’s a full 2″ overlap of the Kerdi on all long edges, but not necessarily at the points where 3 corners meet. Seems like there would be a possibility for a slight gap at these points.

    • Roger

      Hi Adam,

      It’s always best to use the preformed corners when you have them.

  • Meredith

    Hi Roger,

    I have been following your waterproofing guide with a liquid membrane. I already built the niche and purchased Redgard to waterproof it, however I am having a hard time finding fiberglass tape to embed in the Redguard in the corners of the niche (they don’t have it at Lowes or Home Depot). My question is, can I just use thinset and cement board tape to fill all of the corners of the niche and then Redgard over the entire thing? I’d rather not pay $$ and order mesh tape online.


    • Roger

      Hi Meredith,

      Yes you can.