A Flawed System, Shower Pan Liners
I would like to start this post off with an apology for my lack of artistic skills. I am a contractor not an illustrator. Now that that is out of the way, let’s talk about my experience last week.
On my current bathroom remodel the township wanted an inspection of the shower pan. They required the drain to be plugged and the pan to be filled with 2″ of water. I have to admit that this is the first time they had ever required an actual separate scheduled inspection of this. I have no complaints though, if you stand behind your work, it should pass a water test.
When the inspector got there, he looked at the pan and said that everything looked good. I used the Kerdi membrane on top of my mortar base which is a topical waterproofing. This means that any water that passes through the grout or tile never enters the mortar base as with a traditional PVC pan liner and clamping drain. It simply hits the Kerdi membrane and then travels through the thinset and into the drain.
I then proceeded to ask the inspector that if someone were to use a traditional PVC pan liner, when would they want to inspect? Prior to the secondary mortar bed being installed (after preslope and panliner), or after the secondary mortar bed was installed. He told me that you only need one mortar bed, so you would schedule the inspection after that is installed. That you can install the panliner directly onto the subfloor, float your mortar over top of this, and then install your tile. Adding, that the only way water would ever hit the liner is if the tile cracked or mortar bed failed, and this would be the tile installer’s fault.
I was shocked to hear this coming from an inspector. This is completely wrong, and I have removed countless failing shower pans that were installed the same way (one even had worms living in it). I politely mentioned this to him, and he didn’t seem to budge, so I just shut my mouth (I had not received my approval sticker yet). Let’s explain what is wrong with what he told me.
The wrong way
Here are a list of problems with the installation above:
1) You would have to install metal lathe or reinforcement on top of the PVC liner risking possible puncture.
2) Once the water makes it’s way through the tile and/or grout (tile/grout are not necessarily waterproof) it will trickle through the mortar bed and hit the panliner. If this panliner is not pitched toward the weep holes in the drain assembly, the water has nowhere to go.
3) Once enough water saturates the mortar bed from constant use, it will weaken it to the point of failure. At this point the mortar bed will become completely saturated and begin to mold.
Now let’s discuss the proper installation.
The right way
Here is why the above install is correct:
1) The metal lath or reinforcement can be placed on top of a cleavage membrane on top of the subfloor. It will never come into contact with the pan liner.
2) The preslope under the pan liner channels any water that gets through the tile/grout into the weep holes in the drain assembly.
3) If the mortar bed were to fail and the tile or grout cracked, the water that makes its way into the mortar bed would be once again channeled into the weep holes in the drain assembly.
4) The pitch for the shower floor is created with the preslope, and the secondary mortar bed is all a uniform thickness.
As mentioned I do not use this type of shower pan system, but many guys still do. I can quite honestly say that I have never removed one that was done correctly. The fact of the matter is that if it were done correctly, it wouldn’t need removal/replacement. This is a major issue that plumbers, tile setters, and most of all inspectors should be aware of and putting into practice. These types of shower pans are constantly getting a bad rap because of consistent failures. The truth is though, that if installed correctly there should not be any issues with the shower pan. So the actual ‘flaw’ in the system is with the installers/inspectors and their lack of knowledge, not the system itself.