Fixing a Leaking Shower Curb

What to do with a busted shower?

It’s a question that I get pretty frequently. There are lots of ways that traditional shower waterproofing can be compromised. One of the most common is a careless tile installer shooting screws or nails through a fiberglass or PVC vinyl waterproofing liner wrapped around the shower curb. Since this problem usually takes a few years to become apparent, the original installer can be long gone before their shoddy work is noticed.

DON’T puncture shower curb fiberglass!

In this case, the client had a shower that was installed with a badly sloped tile floor from the getgo. The client had always been annoyed by having to squeegee standing water to the drain with their foot after every shower, but figured this was just an inconvenient annoyance from having picked a not so great contractor.

However, after a few years the outside walls on both sides of the shower curb started showing signs of water damage. That indicated failed waterproofing. The bad shower floor slope was a leading indicator for more problems.

That sucked, because the traditional fix for a compromised shower waterproofing liner is a compete tear-out to the studs for starting over. However, that’s a sledgehammer solution to perhaps a smaller problem. If an old-school fiberglass or PVC shower “pan” waterproofing liner is leaking but the shower walls are well done with tile on concrete backerboard, then it’s often possible to tear out and replace just the base of the shower (everything from ~12in off the floor down) for about half the cost of replacing an entire custom tile shower enclosure.

Or, if the leak is confined to just the shower curb, then it can be possible to demo just the shower floor and concrete base down to the fiberglass waterproofing liner and then repair and rebuild the shower floor without carving into the shower walls at all.

This client wanted to try a relatively easy fix process for an improperly sloped shower floor and leaky shower curb. Did it work? Read on to find out!

Try a smart fix!

Careful demo excavation!

Step one was to carefully remove the existing shower floor tile to figure out what kind of construction was used for waterproofing and whether the existing waterproofing could be patched and left in place.

In this case, the previous installer had used a very traditional fiberglass waterproofing pan with a concrete deck mud base. That was good, but unfortunately they compromised the shower curb waterproofing by punching a bunch of nails through the curb wrapping. This is the equivalent of making a wonderfully waterproof submarine but screwing it up at the final step by installing a big ‘ol screen door instead of a watertight main hatch.


Not my first rodeo on this type of shower fix. This is a common problem, and it was possible to carefully crack out all of the concrete base to fix the shower curb waterproofing without tearing into the shower walls at all. Just the shower curb waterproofing needed fixing.

Replacing just the shower floor tile is a lot less expensive than demolishing and replacing an entire shower. And, with the waterproofing fixed, the result would be a correctly constructed and properly sloped shower floor base that’ll last for decades. Plus, the client got to choose their own new tile for a way cooler modern art deco look!

Step ONE: Uncover, investigate, and add peace of mind

Look, it’s X-Ray vision!

Chipping into shower installs is like grabbing a chocolate from the lost lid box. You never really know what you’re gonna get.

In this case, removing the shower floor tile and base uncovered a solid traditional fiberglass waterproofing pan that was properly installed. Aside from the nail holes on the curb, the pan was properly bonded to the drain assembly and properly wrapped up underneath the concrete backerboard wall tile substrate.

Added “RedGard” waterproofing

Whomever installed the shower floor tile had simply screwed up on the slope and ignored the nails that some dumb backerboard installer had pounded through the fiberglass waterproofing pan wrapped around the 2x4s that framed the shower curb. A competent fiberglass installer had done the waterproofing liner but then some dopey incompetent tile installer had screwed things up from there.

The good news was that this could be a very clear cost-saving repair. The shower pan waterproofing was fundamentally sound, so the fix was pretty straightforward. Just carefully chip out the existing floor tile and concrete base, and then apply some thick coats of paint-on RedGard elastomeric waterproofing to seal the curb (and all over the existing pan, just for peace of mind).

Step TWO: Make the slope correct

Forming and Packing: proper slope takes effort

A traditionally constructed shower floor has about 2-in of packed concrete ‘deck mud’ (also called ‘dry pack’) sitting inside the waterproofing shower pan. This concrete layer forms the shower floor slope towards the drain (at least 1/8″ over each foot of run), and the shower floor tile gets installed on the concrete. While the deck mud concrete layer is not waterproof, it does give a nice stable base and (if sloped to drain correctly) dries out nicely between each use. Although not quite as mold-proof as it could be using the latest waterproofing materials, a traditional shower base will nevertheless last for a few decades when installed properly.

Concrete deck mud slope almost done!

I personally prefer a more modern approach that uses Kerdi waterproofing fabric to put the waterproofing layer immediately underneath the shower floor tiles, but that’s not an option with a retrofit fix. The one thing you want to avoid at all costs is any construction that traps water with no easy escape. In traditional shower construction, any water that gets absorbed by the concrete base simply evaporates back out through the floor tiles. And this traditional waterproofing approach is fine for a shower that (just like a composite shingle roof) just needs to be reliably waterproof for 20 years or so.

Step THREE: Install the tile

Concrete Base: ready for a cool tile finish

With a properly sloped concrete base, installing the shower floor tile is just a matter of making sure the grout lines all line up. The client chose small round porcelain penny tile, which actually takes extra special care for even grout line installation.

Although every sheet of mosaic tile is identical in a perfect world, in the real world each sheet is slightly different. Slight irregularities in the factory placement of the edge pieces means that some seams will be wider than others unless you carefully lay everything out first.

Basically, it’s a jigsaw puzzle made of pieces that should be identical and therefore interchangeable, but actually aren’t. So, the trick is to test fit each sheet of tile to find just the right perfect orientation for each.

Mosaic tile install: guidelines a must!

Once you’ve test fit the sheets to make sure they will actually fit together seamlessly and also fit the floorspace evenly, it’s a must to then carefully label the position and orientation of each sheet. In short — write it down! Mark and number the sheets with some masking tape, and then draw yourself guidelines on the concrete surface you’re tiling.

The trick to not messing up on tile placement is to minimize thinking! So, do all the thinking during the planning. Don’t think while installing. That’s usually a recipe for wiggly grout lines.

Grouted and ready!

Step FOUR: Re-Install glass and appreciate the results!

All sealed up and ready for use!

The main challenge to repairing the waterproofing on a leaky shower curb is managing to do it without changing the shower dimensions in any way.

Frameless glass doors and partitions are expensive. And, they’re custom sized and cut to the exact dimensions of the finished tile work. If you remove the glass and then redo the tile, you can’t re-install the original glass unless replacing the tile didn’t change any of the measurements. Like, at all.

For this repair, that simply meant installing the replacement shower curb tile to the precise height of the original to ensure that the glass shower door would close. It was actually possible to do this while also properly pitching the angle of the tile to ensure that water running down the inside of the door would drain into the shower instead of leaking out the bottom door gap. The curb wasn’t properly sloped for this before. Now it is!

The client was very happy with the results. No more water weeping through the curb, no more dead spots in the shower floor, a way more stylish tile, and no more standing water on the curb to boot. Excellent!