This post describes the top, or overlay, of the curb for your traditionally waterproofed shower floor with a liner. The stuff you stick the tile to. It assumes (my posts often assume quite a bit – they are condescending little bastards…) that you already have the curb substrate built, your preslope in, and the liner installed. Those steps are described in the first couple of posts showing you how to build all that stuff here: How to create a shower floor for tile.

First I’ll answer a few questions I get constantly:

NO, YOU CAN NOT INSTALL HARDIBACKER TO YOUR CURB FOR YOUR TILE! (Unless you are using a topical waterproofing method for your shower floor.) There is no way to attach the hardi to your liner without puncturing it, which renders your waterproofing efforts useless. You need to have wire lath over your liner to hold it to the curb  and wet mud installed over that to form a substrate for your tile.

Yes, you can use deck mud for your curb if you want to. However, it is not nearly as stable on the sides of your curb. It is not sticky. It may fall off the sides of your curb even after it cures, and take your tile with it. And it may crumble as you work with it after it cures, because you can’t pack it tightly enough to be dense enough on your curb. But yeah, you can use it… :D

No, you can not bond tile directly to your liner. No, you can not bond tile directly to your lath. Neither will last. Ever.

When you create your shower floor you are using deck mud. You need wet mud for your curb due to the vertical surfaces. Wet mud is almost identical to deck mud, it just has powdered masonry (or hydrated) lime added to it. A proper wet mud mix is 1 part portland cement, 1/2 – 1 part powdered masonry lime, and 4 parts sand. It is mixed just like deck mud except it needs more water. It should be the consistency of peanut butter (the creamy, not the chunky…)

Powdered lime is nasty stuff! Do not get it on your skin, it itches and burns at the very least and some people have horrible allergic reactions to it causing nasty rashes. Do not breathe it in! Seriously, it’s nasty stuff, handle it with extreme care.

Quikrete stucco base coat

Quikrete stucco base coat

But there is an easier way! I now usually use stucco base coat in place of wet mud when doing smaller areas such as just a curb or bench. It is a very similar mix. Although I don’t know what the exact ratios of the ingredients are it works and cures exactly like my wet mud. It is pre-mixed and bagged and you can find it in the concrete section of any big box store. So I’ll show you how to do your curb using that. Should you choose to mix your own wet mud everything is exactly the same.

Once you get your liner installed and all your dam corners in you need to cut strips of wire lath  to fit over your curb. USE GLOVES! Wire lath is sharp and will slice the crap out of your hands! So wear gloves and be careful.

Measure from the liner to the top of the curb, up over the top and down to the floor on the outside of the curb. Subtract an inch from that measurement and this is how wide you want your strips to be. Once you do that cut it the length of your curb.

All the photos I have are of a double curb with a 90 degree angle. If yours is just one curb across the front of your shower it works the same way, but I get a lot of questions about these as well. You can click on any of them for a larger version.

Bent lath for curb

Bent lath for curb

Bent lath for curb

Bent lath for curb

After you get your lath strips cut you need to bend them into a ‘U’ shape. Measure the distance from your liner to the top of your curb and mark that on your lath. That will be your first fold. Fold it all the way over onto itself, not just a 90 degree angle. You want to overbend your lath so that when you put it over the top of your curb it will hold the liner in place.

Your second bend will be the width of your curb away from the first. If you have a 2×4 as your curb just take a scrap 2×4 and place it in the nook of the first fold and fold it around the 2×4. Same works if you’re using bricks. Once folded your lath should look like the photos on the right.

Take the lath and place it tightly over the liner on the curb. You can nail the OUTSIDE of the lath to hold it in place, the deck mud for your shower floor will anchor the inside. DO NOT nail the inside or top of your curb!

Lath wrapped over the curb

Lath wrapped over the curb

Lath wrapped over the curb and corner

Lath wrapped over the curb and corner

The lath should fit snugly against the liner. Overbending it like you did causes it to spring against the liner rather than flapping in the wind. ‘Spring against the liner’ isn’t exactly the best description, but it’s the best I can come up with. Damnit Jim! I’m a tile guy, not a creative novelist!

If your curb is created out of brick you obviously can not nail the outside of it. The spring action (see, now it’s an action and everything…) will hold it in place.

The lath DOES have the ability to puncture your liner! So you need to be a bit careful with it. But you do not need to baby it, the liners are much more durable than you might think. In other words – don’t be afraid to touch the liner with the lath. :D

Once it’s in place you have an anchor for your mud so it will stay in place. Once the mud is packed onto the curb it will pack up under the wires of the lath and hold in place. With the outside corner, like this shower, I also cut an additional small piece of lath to wrap around the top of that corner, like the second picture of the lath on the curb.

Properly mixed stucco base

Properly mixed stucco base

Once your lath is on the curb go ahead and install your top mud deck. That part can be found in Part 4 of creating a shower floor.

Now mix up some stucco base coat. The water ratios on the bag will actually give you about the correct consistency, but begin with a little less water and add a bit more as you mix just to be sure you don’t get it too thin (runny). Again – it should be about the consistency of peanut butter.

Packing mix into the lath

Packing mix into the lath

YOU DON’T NEED TO MIX THE ENTIRE BAG! :D I just put that there because I know somebody will. You just need enough for the curb. I don’t know how much that is, I can’t see your curb. You can always mix more if you need to.

I use a magnesium mason’s finish float to form and finish my curb (and decks) but you can also use a wooden float or flat trowel if you don’t have one.

(very) rough finish on curb

(very) rough finish on curb

Once it’s mixed just start by scooping a bunch of it onto the lath. Pack it into the lath well by running your float both ways to ensure it’s embedded beneath the wires of the lath, then start forming your curb. Ideally you want it about 1/2″ thick, but there is no real number for the thickness, so shoot for that. It’s not a big deal if you get it a little thinner or thicker than that. It’s just a guideline.

Packing and embedding mud into lath

Packing and embedding mud into lath

You want to make sure that every side of your curb is straight (flat). You don’t want them to be wavy. You also want the top to slope slightly into the shower so water will drain into the shower rather than out of it. Your wood or bricks should also be sloped beneath the liner, but you want the tile on top sloped as well to rid the curb of most of the water.

Finished mud on curb

Finished mud on curb

To finish the mix off and get a nice, smooth finish, dip your float or trowel in water and run it down the curb. It will smooth it all out. If you have any rough areas that just seem to get worse the more you mess with it (and you will) – leave it. After it cures you can always sand it down a bit to remove any uneven areas. Just make sure you have enough to sand down – that it’s overbuilt rather than underbuilt.

Finished curb ready for tile

Finished curb ready for tile

It’s much easier to sand down to get what you need rather than trying to add something to the curb to get it where you need it.

Your curb does not need to be perfect! Oftentimes (typed with my pinkie in the air) the more you mess with it trying to get it perfect, the more you’re gonna screw it up. As long as it is flat (straight) and the top is level and sloped to the inside of the shower you can fix any imperfections after it cures or make up for inconsistencies with thinset as you set your tile.

Once it cures it’s ready for tile. You can bond tile directly to the curb now with thinset, it’s all ready to go.

Now, if you please, a moment of silence for the reader’s dog who burst into flames this morning because he tried to bond tile directly to the liner. You know who you are. And no laughing at him, before you read this you didn’t know how to do it either. (And he IS NOT the first one to do that!).

The dog in question is fine – we just had to snuff him out…

{ 379 comments… add one }

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  • JayGuda

    Roger, thank you for the very detailed tutorial. My shower floor and curb came out perfect. It’s now ready for tile. Appreciate the time you took to teach us and share your knowledge.

    Reply
  • Billie Young

    The curbside is built. What product do you use to cover curb? Is Corean the only product that can be molded to cover three sides w/o showing grout lines.
    If I need to grout three sides for curbsides, how do you do it?

    Reply
  • Brent

    Hi Roger, I just wanted to say thank you so much for your insight. I have been dreading this project, and with your knowledge, it has made it all so so much easier!!

    One quick question. I am having issues with the lath. The lath wasn’t perfect sitting on the brick/pvc base, but I assumed (yeah big mistake), that I would be able to mold the lath into place with the stucco cement. I put my stucco cement onto the curb, and found the lath to almost “float” in it, so now as the stucco dried, the lath is visible. The actual cement is approx 1/2 -3/4. With your expertise in this area, how can I un-screw this problem? should I add a second thin coat, leave it and fix any imperfections with thin set (the curb will be covered with marble pieces), or break it up, re bend the lath, and try for round two?

    Thanks for everything. Your website is invaluable. I will buy your instruction manual just to thank you, and add to your beer fund.

    Reply
  • John

    OK, I asked about this on your mud for pans blog but did not receive an answer so will try here as it is a little related. I purchased my Portland cement and sand before finding you and buying your books. Anyway, I made my slope 5:1 over lathe over tar paper and all looks great. Liner in, vapor barrier on reinforced and straightened wall studs. Somehow my Portland cement has turned into Portland cement Plastic Cement. As your stucco base probably uses plastic cement my question is will my preslope be OK? I have since purchased regular portland cement for the top layer and have lime on hand for my curb and bench top. Please make my day and tell me not to worry about the bottom plastic cement preslope!

    Reply
  • DIY Momma

    Your guide is exceptional! I didn’t give the shower reno a second thought as we started taking the tile off the walls…but panic sank in when we took up the floor. I think I would have hired someone to clean up my mess had I not found your site.

    I do have a question about the curb. I’m on concrete so installing a brick curb. I purchased a piece of corner lath (all I could find at the store) that I thought would fit my curb. Well I measured after I got home and realized I’m about two inches short from completely covering the curb when I bend it into a U shape. Would it be possible to cut several strips across the width and place them side-by-side over it? Or do you think they’d shift and create chaos? Lord knows I don’t want my dog to burst into flames, and so far through this project he’s been unscathed. I definitely don’t want to screw it up now.

    Your wisdom and guidance are much appreciated.

    Reply
  • CW

    Hi Roger,

    As a preventative to the lath puncturing the liner, could you glue tar paper to the liner over the curb before pouring the bed? I have seen some glue tar paper to the pre-sloped concrete to prevent abrasions on the liner. It may be overkill, but I would prefer that than under…

    Thanks,
    CW

    Reply
    • Roger

      Hi CW,

      No. Why would you want constantly soaked tar paper in the bottom of your shower? The liners are stronger than most people imagine, don’t create problems where there are none. :D

      Reply
      • CW

        🤦🏼‍♀️ True enough. Thanks for reply!

        CW

        Reply
  • Dave

    I like your comments and suggestions. The only thing I haven’t done, according to your web site, is installing the curb lath before I put in the final floor mud. It’ like the instructions for diffusing a bomb. Reader “Cut the blue wire”. Diffuser “OK.” Reader “But first……” I am not complaining. It’s just going to be more of a challenge to make sure the lath stays where it is suppose to stay inside the floor pan.

    Reply
    • Roger

      Sorry Dave, it’s stuff I don’t think about so I get that little lull in there at times.

      Reply
  • Mike

    So, I basically prepared the sill the same way that you did- with one exception:
    Once the lathe was on, I formed the sill with wood and filled it in with sand mix.
    It came out great, except for one thing- My tiler thinks that the sand mix is so porous, that the wet bed water will cause the sill to soak up and stay wet. And once that happens, swelling will result. Bear in mind that the sill is sitting on sub-floor plywood on the outside of the shower. Two remedies I can think of: Somehow waterproof the sill with concrete sealer, or grind a slot on top of the sill and fill with epoxy. Am I losing my mind?

    Reply
    • Roger

      Hi Mike,

      Yes, you’re probably losing your mind – but let’s deal with the sill and your psychiatrist can deal with the mind stuff. :D

      All you need to do is cover the mud with a topical membrane. That can be a liquid like redgard or hydroban, or a sheet like kerdi. The sand mix is porous, it’s meant to be by design.

      Reply