The complaint about discoloring of natural stone on shower floors has become so common that TCNA (Tile Council of North America) has placed a cover letter in its Reference Manual. To summarize. No one is to blame. There is no way of knowing which stone will show this. It is the risk you take when using natural stone in a wet area.

It can happen with a water-in / water-out system (mud job w/liner) or a bonded system (topical waterproofing).

Sealers are not the solution.

There are so many porcelain marble look tile that you can use. Especially on the floor. I would not go with marble.

If practical considerations entirely drove shower construction, then relatively soft natural stone like marble would not be used in showers. In fact the whole idea of using tiles with non-waterproof grout lines is pretty silly when you think about it. You just need something waterproof to line a shower. Obviously people don't want to look at Kerdi or Hydroban and Choreograph isn't as popular as I'd expect and the look and feel of one piece enclosures makes them undesirable. So tile is the default cover and if you are going to do that I'd use a hard ceramic tile and minimize grout joints.......so avoid marble, it might look nice, but when there are so many beautiful marble effect ceramic tiles why would you give yourself the worry and expense of marble?

If you DO end up using a marble mosaic, I can not recommend strongly enough-- DO NOT SEAL IT. Almost guaranteed you WILL have problems.

Even if sealing it works at first, it should be renewed periodically. How often? Depends on the characteristics of the stone. The problem many people have is remembering to clean and reseal it in perpetuity. Save yourself regrets and repetitive maintenance and go with a marble-look porcelain tile.

save the headaches and the money, porcelain is the way to go.

I would suggest a textured tile. these tend to be the least slippery and look great in a bathroom. marble or even shiny tile is very slippery and dangerous. there are a lot of nice porcelain options these days. there is also wood tile that looks like wood in many different shades and colors.

We have 2" porcelain "marble look" hex tile on our shower floor. It's not slippery at all & we have small children that use it daily. It's more about tile size & grout lines that will make it slippery or not. I would avoid real stone in the shower at all costs.

I agree with mark_rachel-

In one shower I have 18" square porcelain tiles on the wall that are super slippery. On the floor, I have the same tile in a 2" X 2" size and there is plenty of traction from the grout lines.

The problem is that moisture can become trapped in the stone and discolor your stone, making the floor look blotchy. No matter HOW well you seal it. I had this issue with a customer, and ended up replacing the shower floor as a result. Once the floor was replaced (calacotta gold mosaic), the customer did NOT seal it, and the problem never presented itself again.

Super KEY here, when you seal a marble shower floor you want to use A vapor permeable sealer such as Miracle511. It will allow moisture to migrate out thru the sealer.

I'm telling you, no. The sealer that was used on the floor that I replaced WAS 511 Impregnator.

For more examples of what Bill Vincent is saying, simply go to the top of this page and do a search in this forum on "Marble Shower Floor" and you can read for hours the experiences of both homeowners and the pros on what problems they have had with it. Pictures, too!

hogwash. I have 20 plus showers in homes now with marble and 511, steam rooms too bill, it is a breathable vapor permeable sealer.

Perhaps your single case study has faulty factors in the investigatory category LOL ....id hug you right thru this phone if i could

I had some of the best minds in the industry working on this, from other contractors and John Bridge, to manufacturers reps and even Dave Govis weighed in. Not one person could come up with aan explanation that made sense. It was when no one could figure out the problem that I decided to tear out the entire shower floor and redo the whole thing on my dime. The ONLY thing that was done differently, was that the mosaic was left unsealed. No more discoloration problems after that.

Gentlemen, You have circled back to my point of the first comment on this thread. As I know both of you and respect your points of view. A few months back I also contacted folks to see where the TCNA Tech committee stood on this. The letter in the reference manual is where it stands at this point. No verifiable explanation. Just a warning.

We all shall continue to use our years of field experience and research to provide what we feel is the best methods available.

Best to all!

Id agree. Avoiding marble is the answer. I do respect Bill btw. Ctec too and you know im an TCNA deciple.

Lets just be clear. 511 is a vapor permeable sealer and is the smart choice (or any permeable BRAND ) if you are to seal a marble shower floor. Can wacky crazy stuff happen and sometimes never reveal the answer? absolutely. Some folks see ghosts .

Trying to keep up with the latest testing.

Update to this thread.

Article dated July 2020

http://tileletter.com/2020/07/marble-moisture-discoloration/

NOTE research continuing.