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-   -   Kerdi shower leak (https://www.johnbridge.com/vbulletin/showthread.php?t=128678)

Randmfernandes 02-01-2020 01:07 PM

Kerdi shower leak
3 Attachment(s)
Good day
We installed a DIY kerdi shower. We used kerdi membrane, the polystyrene pan, but built the curb from plywood. We did not cover the plywood with cement board. Only membrane. We took great care installing but still our shower developed a slow leak.

We had kerdi inspect. They said our problem was that we had not used cement backer board. They seemed to think that was the root of the problem.

I have now opened the tiles to see what is going on. It looks like the problem is an area where membrane is not properly bonded.

My question: can I fix this area by filling the gap with thinset and applying kerdi membrane / band or do we really need to rip out the curbs and replace with kerdi curb or apply cement backer board? How significant was this mistake we made. Any advice is appreciated.

Davy 02-01-2020 01:43 PM

Hi Marle, welcome.

First of all, do you have any left over tiles from this installation or can you get more to do the repairs with?

What's behind the Kerdi on the walls?

I'm not a Kerdi expert but I would remove the door and curb, that way the curb can be rebuilt back. Before doing any demo, take measurements so the curb can be built back exactly as it is now, that way the door will fit back.

Get the curb and Kerdi work done and do a flood test before setting any tiles back.

Others will be along to help.

Houston Remodeler 02-01-2020 01:54 PM

This isn't looking like it would be an easy repair as removing the tiles damages the kerdi.

As much as I hate to say it, this would qualify as a re-do. The hard part of any shower is the floor area, so the walls are the quicker, easier section to re-do.

When the glass was installed - was the kerdi membrane penetrated with fasteners?

Dchesky 02-01-2020 01:58 PM

Based on what I’ve learned about kerdi membrane, it cannot be directly applied to wood. It has to be either gypsum, cement board or some other suitable substrate. That is the problem. So unfortunately you will have to remove the curb entirely and reinstall a kerdi curb or build one with 2 x’s and cover with densglass, cement board or even 1/2” kerdi board. Use the band to waterproof all seams and screws in the curb and inside outside corners before tile.

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Randmfernandes 02-01-2020 02:05 PM

Thanks for reaponses so far. We have green board behind shower walls covered with membrane. We thought we isolated the leak, through testing, to the floor and corner around curb area where i pulled out tiles.

When we installed the shower walls/ door we did penetrate kerdi. We put silicon on the screws. Do you recommend an alternate method?


Davy 02-01-2020 02:15 PM

Try to answer any questions we have, it helps us help you. Any left over tiles?

I wouldn't say it's a redo at this point but could end up being that. I think it's worth trying to fix although the time needed might take as long as a redo.

Randmfernandes 02-01-2020 02:29 PM

Sorry davy. Missed that one. Yes we have enough for a repair.

Davy 02-01-2020 02:36 PM

In that case, I'd try to repair it. I do think you'll have to remove more tiles on the wall in that area and hope the Kerdi isn't damaged in the process.

makethatkerdistick 02-01-2020 04:27 PM

To me, the Kerdi seams look awfully loose. Is there air under these areas, or is it an excess of thinset?

Regardless, if you are attempting a repair rather than a redo, I'd probably use Kerdifix to inject into those areas and smear across the seams to achieve a better seal. If you use thinset, you might end up with too much. This will keep wicking moisture. The Kerdi system only works properly if the thinset under the seams is applied thinly and has full coverage. And even then, it needs to dry out between uses. If there is too much wicking going on, then it'll essentially never get dry and keep slowly leaking.

If you have to remove strips of the Kerdi membrane, keep in mind that it will result in the fleece being torn off at least from one side of the membrane, thus making a potential bond to a fresh piece of Kerdi virtually impossible, at least with thinset. I am not sure if the Kerdifix will attach de-fleeced membrane to fresh membrane. It might. If that is a problem for you, you might want to ask Schluter about it.

The green board is also somewhat of a mistake, albeit a smaller one. Its surface is waxier than that of normal drywall, thus potentially diminishing the bond between it and the Kerdi. Regular drywall or cement board are a better choice.

Lastly, if you want absolute peace of mind, this would have to be redone properly, unfortunately. But by all means, give it a shot with the repair.

Kman 02-01-2020 06:51 PM

Regarding the screws on the shower door, were any driven into the curb, or just the walls?

Kman 02-01-2020 06:51 PM

And in what order was the Kerdi installed, floor or walls first?

Tiger Mountain Tile Inc 02-09-2020 01:41 PM

I agree with Wolfgang. If it's your shower and you want to try to fix it with as minimal impact as possible I would try the Kerdi fix route. Test it before covering it with tile but keep an eye on it from here on out.

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