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HomeTechnicalAsk the ExpertsRepairing a shower pan using TCNA Method TR420

Repairing a shower pan using TCNA Method TR420


Section TR420-23 Shower Receptor Renovation in the TCNA Handbook refers to new bonded waterproof membrane. Is this an approved method for a topical sheet membrane? I haven’t got the 2024 Handbook yet so I don’t know what – if anything – is updated. Just looking for clarity if it would be an approved renovation/repair method, of course assuming that the manufacturer approved.


Thanks for reaching out to the NTCA Technical Team with a great question.

As you know, TR420 is a TCNA method designed for repairing a shower pan. I have confirmed there are no changes to this method in the 2024 TCNA Handbook. A committee is reviewing this method.

That being said, this can be a very difficult method to achieve for a few reasons. One is that renovations in general are more difficult due to the fact that we don’t know what we’re going to find when we open the walls and remove the shower pan. Another reason would be because we don’t know the quality of work that was done and we are now being asked to fix.

Method TR420 is designed to help give a path on how to repair a shower that utilizes a new shower pan as well as a new bonded waterproof membrane (sheet membrane) on top of the mud bed while using a three-piece clamping drain.

There is currently no method showing how to repair an existing tiled shower using a bonding flange drain. What you are describing is a mix/hybrid of two different methods. (as an example – B415 walls + B422 shower pan).

I completely understand your reasoning for using a bonding flange drain, but you would be outside of a TCNA method, and would need to rely on written manufacturer instructions for how to properly achieve this repair.

One thing I think many contractors and installers may agree on is that when a shower is leaking, it is a best practice to do a full tear-out to guarantee and warranty your new work. Any time we are doing repair work as tile contractors we need to be very cautious about taking ownership of someone else’s work or offering a warranty on work that someone else performed years ago (i.e. in the case of you repairing the pan but the walls are original). Taking on this type of repair work would likely come down to a business decision. How much risk/liability is your business willing to take on? The answer to that question will vary from business owner to business owner.

I hope this helps add clarity to this method. If we can help in any other way, please reach back out.   

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