Creating a threshold or curb for your shower

by Roger

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…

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Kyle

Great site!! :)

I bought a 6-yr old condo apt with some issues in the travertine tile shower. You’ll like these! :D

All of the corners / plane changes are grouted (and therefore all cracked). Those at the floor had somebody’s silicone “repair” over the grout, which weeped water when I pulled it off.

There are grout cracks between the 2×2″ floor tiles, but the tiles aren’t loose. These cracks were always wet / discoloured, and appear to be weeping water up from under the grout.

Also got “wet bugs” now (silver fish, milipedes, wood louse…). Found gaps under the curb caps (Corian) that had grout, not silicone. Most grout was gone leaving a gap for water to get under the caps. I removed the glass walls and the Corian caps came right off the curb with them. They were not stuck to the curb, only the silicone on the glass walls held them there!

Mould and bugs under the caps. Gaps/cracks where the curbs meet the walls, giving a leak path for water to get behind the wall tiles and/or over the curb.

Since the grout weeped when I removed the caulking “repair”, I take that as a good sign that water was still trapped within the shower behind the grout/tiles, and not getting outside the shower much. (The bugs make me wonder through…)

All tiles are still attached very solid, on the wall, floor and curb.

On the curb is about 1/2″ of pinkish mortar(?) that failed to grip the smooth Corian caps (and not sloped toward the shower). Under the mortar is white non-metallic mesh, 1/4″ squares. Don’t know what’s under that, or if it has a membrane.

My plan is to remove all corner grout (oscillating tool with grout blade) so they can be siliconed.

Should I also grind and regrout the cracks between the 2×2″ floor tiles? Or just leave them as is?

For caps, how could I remove the topmost mortar without damaging the stuff under it?. And should use Corian at all for the caps? Early search suggests maybe no. But if Corian is okay, what adhesive/mortar should I use under them?

My hope is with properly replaced caps and sealed up with silicone that water will no longer get under the caps and leak who-knows-where. And replacing the corner grout with silicon will reduce the amount of water that gets under grout/tiles.

Many thanks! :)

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Reply

Kyle

Update: Some gentle chipping at one of the corners shows the curb’s construction. It’s wood structure; then membrane that appears to cover only the top of the curb (not the outer face); then 1/2″ cement board on top and sides (that’s the “mesh” I mentioned earlier); then mortar for the tiles on the sides and whatever the pink “mortar” is on top for the curb caps. Oh and there’s a rusty nail through the cement board and membrane into the wood, so it’s been nailed at least at the edge of the membrane into the top of the curb.

Since water was getting under the caps and the structure is wood, I get the feeling the tiles have to come off to possibly replace the curb. Is it possible to do that without replacing the membrane?

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Reply

Nick

When creating the pan was it just liner and bed concrete? Or did you put mesh in their (bottom? middle?) I have a 60×40 shower with a bench I’m doing and was curious. Also I’m running the liner up and over the bench too and using red guard on the walls. Any tips would be great. -and great article

Reply

AStritt

Roger,

Great site! I have preslope, liner, curb and mud pan installed. I’ve also installed most of the wall tile, but it’s time to install the curb cap.

Hydroban was used on the walls and a few inches in on the pan floor.

My question is do I need to apply hydroban to my entire curb before setting the cap?

Thanks Roger!

Reply

Roger

Hi AStritt,

Provided your curb was properly waterproofed with the liner then no, you don’t need to. You can if you want to, though, it really won’t hurt anything.

Reply

summer

I read in my lowes book to install the membrane, then the backer on tge walls, then tile the walls, and lastly mud and tile the floor. So i finished tiling my walls and i wondered if my floor mud should go right up to my wall tile, touching the tile or if it should go slightly below it? Allowing the floor tile to rest under the wall tile?

Reply

Roger

Hi Summer,

You can do it either way, I prefer the floor tile beneath the wall tile.

Reply

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