How to Fix a Leaking Shower Curb

What to do with a busted shower?

How to fix a leaking shower curb is a question that I get pretty frequently. Traditional shower waterproofing can fail in lots of different ways. 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. This problem usually takes a few years to cause clear symptoms, so the original installer can be long gone before their shoddy work is noticed.

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DON’T puncture shower curb fiberglass!

This 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.

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 fix their leaking shower curb (and also fix the shower floor slope) wihout demolishing everything. Did it work? Read on to find out!

To fix a leaky shower curb, Try a smart fix!

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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.

Don’t put screen doors on your submarine. Also, DO NOT PUNCH NAILS THROUGH YOUR SHOWER BASE WATERPROOFING MEMBRANE!

This was 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. This is how it’s possible to fix a leaking shower curb without ripping out everything for a complete redo.

Replacing just the shower floor tile is a lot less expensive than demolishing and replacing an entire shower. And, with the shower curb 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 shower floor tile for a way cooler modern art deco look!

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

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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 for the most part. 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.

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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 for added peace of mind).

Step TWO: Make the slope correct

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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.

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Concrete deck mud slope almost done!

Although not quite as mold-proof as it could be using the latest waterproofing materials like Kerdi fabric, a traditional shower base will nevertheless last for a few decades when installed properly. 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.

Remember that the goal here was to simply fix a leaking shower curb to make the traditionally waterproofed shower watertight.

Step THREE: Install the tile

Installing shower floor tile is easy if the base is properly sloped. You just a matter of making sure the grout lines all line up. The client for this project chose small round porcelain penny tile, which actually takes extra special care to install without visible seams.

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. The trick is to test fit each sheet of tile to find just the right perfect orientation for each one.

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Grouted and ready!

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

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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!