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Plumber woes; mosaic mockups for happy clients
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Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Team. To become a member and make use of personal, targeted answers from NTCA's Technical Team to your installation questions, contact Jim Olson.
Drain has been moved; plumber won’t move pipe so flange can be set
QUESTION: We are setting a flange in our shower pan. We will float the pan with mortar.
The drain is being moved in order to accommodate proper slope. It would have been too steep in the current location.
The plumber is not willing to move the pipe before we set our flange. He wants us to set it in the pan and the next time he comes this way he will attach the drain pipe. But if he pushes too hard while setting the pipe into the flange, there is the possibility of damaging the waterproofing around the flange. 
My thoughts are to put it in writing what we will do: set the flange in the pan and tile before drain pipe is attached and that if there is damage to the tile or waterproofing, it would be the plumber that pays for the repairs needed.
Should we do that or insist that the drain pipe go in before we set the flange?
ANSWER: I have run into this issue a lot in the past. First, I would talk to the plumber and also let the general contractor know what is going on and explain the liability involved. They both need to understand that you are using a topical waterproofing that could be damaged if pushed on from below.
If that does not get you anywhere and they still are not willing to move the drain for you, then yes. I would get it in writing.
When you follow the manufacturer’s instructions for installation you’ll be surprised at how strong the bond is. You want to make sure the mud is coming up through the holes on the outer rim of the bonding flange. This will help lock it in place. When I have had to do this in the past, as an insurance policy I would use a countersink bit (see picture right) and make the pre-drilled holes in the bonding flange the right size to accept a decking screw or a stainless screw. Install these four screws prior to mudding your pan. As long as you drill the right size hole, the screw head will be flush with the bonding flange, will not interrupt your waterproofing and will help ensure the flange stays in place while reconnecting the 2" pipe from below.
Attached are pictures of the mosaic our customer wants us to install. The back has a lot of glue on the mesh and the stones have a lot of holes that will capture and hold grout. It’s a very dark grout.
We have sealed a single sheet of this and are going to mount it and grout it as a sample before we put it on the floor. We want the customer to see what we will have as a finished product before it is really finished. They are set on stones in the shower pans.
Are we doing all we can to get them the result they are looking for, or is there anything else we can do? Our fear is many of the holes in the stones will show the grout because of the dark grout on light colored stones.
ANSWER: You are utilizing the mockup to its highest degree. Stones with holes and dark grout will yield the speckle effect and possibly client unhappiness. Show them how it will appear BEFORE it is installed. When the mockup is complete, take a photo of it and have them sign it, providing their full approval.
Watch out for the over-glued mosaics. I recently did a demo on flattening the mortar before the installation of a 1-1/2"x3" mosaic that was sheet mounted with a significant amount of glue on the back. Interestingly, when I pulled the sheet out of the mortar, the tiles that did not have mesh and glue on the back had full transfer and 100% coverage. Unfortunately, the mortar did not transfer to the mesh and glue area (bond breaker) and would have been completely unbounded. Test the tile for mortar transfer before setting it for the mockup.
Additionally, you may want to cut the sheet in half before you do your mockup to illustrate the possible sheet mating issues and, if significant, rethink your bid. Hand setting is an art, but it needs to be compensated appropriately.
RESPONSE: We have spoken to the customer this morning and are now in the process of hunting for a different mosaic. They were happy with the look, but this morning we explained the problems that can come up with the excessive glue on the back. Our customer is a professional electrician and appreciates us explaining and looking out for his showers.
Thank you all for your help. The information we get from this email address is more than worth the NTCA membership fee!