Questions About Tile Over Tile Plan for Walk-in Shower - Tile Advice

[SanDiegoChip]

Hello,

Just joined the forum and am hoping to get some advice on a project. I live in San Diego, CA. My wife and I have been unhappy with our master bath walk-in shower floor since we bought the house 25 years ago. We do not like the aesthetics and the floor always looks dirty. For the last 10 years I have kept a deck scrub brush in the shower to scrub it every now and then to keep it presentable. Several years ago I tried to solve the always dirty problem by sealing the entire floor. This was a multi-day project where we acid-washed the floor and then applied an industrial sealer (I could look up the name of the product if needed). The floor did look better for a while, but it still did not look great.

I am now motivated to finally solve this issue. We found a ceramic tile mosaic at Home Depot that we both like. Rather than demo and replace, we want to lay the new mosaic directly over the existing floor. I have done some research online (YouTube videos) but would love to get confirmation from experienced people in this forum that my plan is sound. I will be doing this project with a handyman I have worked with for over 15 years. He is experienced with tile but is not a tiling expert.

I have uploaded a picture of the shower floor as it is today (after I spent a solid 30 minutes scrubbing very vigorously) that also shows two sheets of the mosaic we picked out. Structurally, the floor is in excellent shape. We have no cracked tiles and no leaks. There are a few cracked tiles in the shower wall along the floor (which I may replace during this project or at least seal). From what I read, the tile on tile should work as long as the original tile is structurally sound and does not have any problems.

Step 1: Prep floor. I am scrapping off the sealer I applied several years ago and will scrub to remove the small amount of mold along the edges. I may also use a hand sander to rough up the floor and speed up the removal of the sealant.
Step 2: Apply two coats of MAPEI ECO Prim Grip directly on the tile as a bond-promoting primer. I wanted to remove/strip the sealer before applying this so it is directly on the current tile.
Step 3: Raise the current drain. Carefully pry up the existing 4" square drain plate. Then use either an Extend-O-Drain product or a homemade 1/4" thick piece of 3" ABS that is glued using marine glue on top of the existing drain.
Step 4: Lay a new mosaic over the existing floor like any other project using a modified thin-set. Use a 17" manual tile cutter to cut the new 6mm thick ceramic mosaic tile. Install a 4" square drain plate.
Step 5: Grout the floor with grout that has built-in sealant.

Q1. How does this plan look? Do you see any red flags? Any recommendations?

Q2. At the local Floor&Decor where I bought the ECO Prim Grip, the technician asked if I wanted to get the Mapelastic AquaDefense t apply first before using the ECO Prim Grip. Is this necessary since the shower does not currently leak and we are not removing the existing floor? Am also thinking I would want the Prim Grip to be applied directly to the tile, not to a waterproof shield.

Q3. My wife is wondering how much it would cost to hire a professional tileer to come in, demo the existing floor, and install the new. My estimated cost for this project, excluding the cost of the tiles which I would buy either way, is $500 for materials and labor. I am also putting in 8-10 hours of my time in prep and installation assistance which I do not mind at all. I assume it would be far more expensive to have a tiler come in and demo/install. Am I correct? I also must admit I enjoy these DIY projects. So as long as I am not creating a headache down the road, I would prefer to do it this way even if a tiler would cost about the same (which I cannot imagine).

Q4. One of the problems with the existing floor is that a small amount of water pooled in a few spots after the shower was turned off. Not a lot but enough for a layer of soap scum to form. I would like to eliminate this by increasing the slope to the drain. Is this something that we can do with the modified thinset or would we need to use something like dry-pack mud? I am not talking about a huge increase in slope. The distance from the drain to the furthest wall is about 2 feet. I was thinking of increasing the existing slope by adding about 1/2" of height at the walls to facilitate a more complete drain.

Thanks for reading this long post and providing any insight!

 

[landon]

hey there, i do remodeling for a living which is mainly just tile work and flooring. i am working on a new constructed house right now actually tiling two walk in showers and two bathroom floors. i’m almost certain it is okay to over lay existing tile, however it would most definitely be better and look better to rip out old floor and redo the whole thing. but either way would work just fine. they make some foam board that you can buy that is already sloped for the drain and would solve your issue of standing water. there’s two kinds we like to use: one being the schluter and two being GoBoard. you would only want to use these if you were ripping out old floor tho. you would definitely pay a professional at least 100-200% more than what you would spend doing it yourself. anyways i hope your shower floor turns out amazing and maybe you can come back here w pics.

 

[SanDiegoChip]

Hi Landon, thanks so much for the input. We were all set to proceed until my handyman came down with Covid. During the delay, after talking with Mapei technical support a few times, and learning we would definitely need to also use their AquaDefense product, I decided to "do it the right way" and rip out the old floor. The Mapei rep said that I could carefully chisel out the existing 1" square tiles using a steel chisel and ball pin hammer. He said it is easy and should just take an hour or two. Unlike one tiler I spoke to, he said I do not need to remove 12-18" of my wall tile and redo my waterproofing/pan. I can remove the old floor without creating leak problems. Any small chunks of thinset/mortar that comes up in the demo process can be patched/repaired. I could also use the patch product to increase my drainage slope. I will look into the foam board options you suggested. Do you recommend one brand over the other or are they equivalent? I will keep this thread updated and post pictures of the process. I probably spent 8 hours scraping and sanding the existing floor getting it ready for the Prim Grip. Cannot believe I wasted all that effort and am going to rip it out now. Oh well, wish I could say it was fun doing that. I'm hoping to do this project in the next week or two.