Let's clarify. You are not tiling over tile. You are tiling over stone. That's a different entity. Two different materials...and the marble is going to be very smooth (hard to get something to grab to it) and it will be sealed (hard to get something to grab that) and it will probably have old cleaning products stuck to the top of the stone (more hard stuff to grab on to). All of that has to be over come.

You can guess how big the chances are for failure.

Photos?

A quick abrasion of the marble would eliminate any contamination problems. If the marble is properly set tiling over it shouldn't be a problem.

Thanks. The marble looks pretty scratched up. No shine to it even after I have cleaned it. I thought I would just refinish it until I realized that I would need a couple of new pieces to match if I enlarged the shower.

It seems to be down pretty solid. We took one of the old L shaped cabinets out that was built in place. The way the cabinet was built makes me wonder how it held up that cultured marble top with built in sink. It has to be at least 40 years old. Very dull marble.

The darker tile was under the cabinet. It is still glossy, but you can't see the shine in the picture.

I found where I could buy new tiles, but I am not sure if it is exactly the same nor not. I would still be left with more of a step down into the bathroom. Even with tile over tile, it would still have a step down but less of one.

Then, I wondered if the tile could be cut out exactly where the shower base would go. (to purple line approximately.) I would not need to find replacement tiles if we can cut it before the grout line. If that doesn't work, maybe I could find a smaller tile to make a design around the two sides of the shower like a border.

Thanks.

It can be cut in place as needed.

It can also easily be tiled over. Mapei & Laticrete both make products for this purpose.

http://www.mapei.com/US-EN/Tile-&-Stone-Installation-Systems/Bond-Promoting-Primer/ECO-Prim-Grip

https://laticrete.com/en/tile-and-stone-installation/adhesives-and-mortars/multipurpose-bonding-primer/prime-n-bond

Thank you. I think cut in place would be easier, but I would have a larger step down, and I would still need to refinish the old marble. It may be less expensive to tile over it. Good to know I have options.

Are you working with a qualified contractor and tiler for this?

Did you save the COUNTER TOP? It looks to be a perfect match to the tiles. A skilled stone worker/tiler *could cut the counter top down to fit the spaces where you have missing tiles.

The shiny bits are the ORIGINAL finish. Your marble can be buffed up and then sealed once again to that level of sheen. That's the beauty of stone. It can be refinished just like hardwood (but with a longer life expectancy - like 200 years).

Go find your counter top and see what can be done. It might work...it might not but you might as well have a look. The material is just sitting there waiting to be used. And it's free.

ProSource Memphis, I wish I had a qualified anything around where I live (rural lake area). I had a very good electrician, but he moved two hours away. My GC will do everything. If he doesn't know how, he has no problem with getting help or looking online. At least he admits it.

SJ, The missing tiles will be on the floor if we have to take them up. But, since everyone has said they can be cut right where they need to be, I shouldn't need any new tiles. The countertop is black cultured marble. I have learned that I hate sinks that don't have places for water to drain into the sink. Water just sits there after someone turns off the faucet and drips while doing it. (and no one seems to dry it off or notice they left a mess.) That is one dark bathroom with a black floor and counter, no window, and medium oak cabinets. I am hoping to use light grays and/or whites in the new countertop.

I found a couple of marble remnants today at $25.00 s.f. and $80.00 more if I use an undermount sink. Not bad for a countertop!

I went to Lowe's today to see The Onyx Collection shower base because my local Be-Mac Supply is only taking phone orders. I can't get in to see anything. The one color I wanted to see was not on any of the samples. Figures! Onyx Collection is sending me some though. I took pictures of the base cut aways they had of the regular height base and the low profile base.

The other solid surface bases I looked at were supposed to be set in mortar. The Onyx Collection base is not set in mortar.

Opinions about that?

I meant using the counter top as a source for more FLOORING tile. It can be cut and installed on the floor if it is a good enough match.

What is your general location? Have you checked the CTI website? https://www.ceramictilefoundation.org/find-certified-tile-installers

Closest is 100 miles away. Four hours driving per day.

Sorry, SJ. The countertop is solid black cultured junk and the floor has black and white veins. I found some marble that may work, or maybe I could use smaller tiles to create a border where the missing tiles would be.

If you can save the floor, I think that's ideal. Especially from a cost standpoint.

If you can't, I really think you should remove the old tile. You can easily install an additional layer of plywood to even out the height mismatch from the hall. You'd need to remove the underlayment/top layer of subfloor to even the floor anyway after you rip out tile. Just thicker material than what was there originally.

They installed the same marble tile in the kitchen. It took us forever to get it off and it came off in very small pieces. I don't know what they used to install it, but it was difficult to remove it. My husband said that he is not touching it. LOL

CTECT:

There is an unjustified tear-it-out mentality here on Houzz. I've seen some tear-outs go very badly and spent an inordinate amount of time removing a properly repaired tile myself.

If you can, leave it.

Thanks, Joseph and Creative Tile.

If I decide to tile over the old marble, after roughing up the marble, do I need to do anything to the grout since is slightly lower than the marble? Or will the troweling take care of that?

Can I lay the 12" tile on top of the 12" tile? Keep the same grout width depending on the tile?