What do I use to adhere porcelain tile to a marble floor?


I'm remodeling 3 bathrooms in an older home. The existing marble 12x12 floor tiles and grout are still like-new. There is no shrinkage or cracking. They were installed with mesh over the plywood sub floor.
What product should be used as a primer/ bonding agent so we can install the new porcelain flooring over the marble floor?


ANSWER - As long as the existing marble floor is structurally sound and well bonded to its substrate without excessive deflection, you can bond over the marble.

The marble surface is likely polished or honed and it might have a sealer on it or contaminates from pass use.  I would recommend first scarifying the surface of the marble.  This will take off any contaminates that could compromise the ability of the porcelain tile to bond to it.

You can apply a liquid applied waterproof/crack isolation membrane over the marble, particularly if there are any non-structural cracks in the surface or if you want a moisture barrier.  But it may not be necessary.

You should use a polymer modified thin-set mortar adhesive that meets ANSI A118.4, or better yet ANSI A118.15, to bond the porcelain tile to the prepared marble surface.   There are flexible thin-set mortars that are recommended for bonding tile over tile too.   Make sure the thin-set mortar you use is recommended for this application.

16 thoughts on “What do I use to adhere porcelain tile to a marble floor?

  1. Scott says:

    Thanks for the info. What is the best method to scarify the existing marble tile ? My marble tile is set on a concrete slab foundation, and I am considering laying porcelain tile over the existing marble to avoid the significant task of hammering the marble for removal.

    • Donato Pompo says:

      Scarifying for smaller areas is normally done with a cup grinder. You can buy them so they have an attachment for connecting a wet/dry vacuum to try to control the dust. Be sure to thoroughly clean and dry the stone after the scarifying.

      There are larger pieces of equipment for scarifying such as bead blasters and other types of scarifying machines.

      Depending on the area you will be doing the work, you have to take precautions for dust control.

    • Donato Pompo says:

      If you want a long lasting durable floor then install a porcelain tile over your existing marble floor.

      The marble floor has to be structurally stable because your new floor will only be as good as the existing floor. You will have to clean and scarify the marble before you installed the tile over it. You will need to use a good polymer modified thin-set mortar for the adhesive.

    • Donato Pompo says:

      Cultured marble is basically a plastic type of material. There are not established standards for adhering tile to cultured marble. Chances are that an epoxy adhesive will bond to the cultured marble as ti will to most tiles. You will have to experiment to see what will work and whatever you do it will be at your own risks.

      The other thing you can do in theory is screw down a cementitious backer board to the cultured marble and then use a modified thin-set mortar to adhere a tile to the backer board. That is assuming that the cultured marble substrate is structurally sound and the backer board and tile are installer per the manufacturer’s directions and industry standards.

  2. Preeti says:

    We have a marble floor and want to change to Italian marble floor.. Can we put Italian marble over existing marble

    • Donato Pompo says:

      Whether the marble was quarried in USA or China or Italy, if it is a true marble then they have some common physical properties even though they may look different. Many marbles are quarried in other countries and then shipped in blocks to China or Italy where they then produce them into slabs and tiles.

      Yes you can bond a marble to a marble if your floor plan can accept the added thickness. Of course the new marble is only as structurally sound as the original marble, so the original marble has to be well bonded.

      Scarify the the existing marble and clean. Then use a polymer modified thin-set mortar for marble to bond the two marbles together. Make sure you install the new marble per industry standards and per the thin-set manufacturer’s directions.

  3. eli says:

    I have marble on a cement shower walls. Has gotten ugly. Cannot hammer to remove because of neighbors. Can I put ceramic tile over it ? Will it stay on like on a floor?

    Thank you!!

    • Donato Pompo says:

      First of all, the good thing about natural stone is that it can be restored. If you get a professional stone restoration company to come in to grind, polish and seal the marble it should look like new.

      It is possible to adhere ceramic tile over marble. First you need to make sure the marble is well attached to the wall. Then you need to grind the marble to remove any contaminates and to give the surface a texture to bond to. You need to use a polymer modified thinset mortar that has more bonding strength. If everything is done correctly, then it perform well.

    • Donato Pompo says:

      Generally speaking the same thin-set dry set mortar used with porcelain tile can be used with installing marble. But check with the manufacturer’s directions which will be on the bag. Normally a white thinset mortar is used with marble as marble can be translucent to a degree and a gray thin-set can affect the appearance of the marble.

      With a 24×24 tile it is important to achieve 95% full thinset contact between the back of the marble and its substrate. All corners and edges of the marble have to be fully supported.

      If you don’t trowel the thin-set mortar in the same direction with the ridges of the thin-set all parallel to each other, you can trap air under the tile that can’t come out leaving a void. So trowel parallel to the shortest tile edge, beat the tile into place with adequate thin-set mortar, and shift the tile perpendicular to the trowel ridges so the thinset ridges collapse into the thinset valleys and that is how you achieve full thin-set contact.

      • Scarlett says:

        It’s so helpful, Thank you very much ! Also, what’s your recommendation for size of spacer for 24×24 marble tiles and what should I use for spacers leave-in or remove one? What kind of Grout I should use sanded or non-sanded?

        • Donato Pompo says:

          It is best to go with a minimum of 1/8″ wide grout joint and to use a sanded grout, which will be more stable. You could use a non-sanded grout in 1/8″ wide joints or less, but the stand makes it more resistant to cracking.

  4. Jatender says:

    Dear Sir,

    I have a marble floor. I want to have room tiles on this marble floor.
    is it good idea or should i remove the marble floor first and then should go for room tiles.
    please reply with your expert comments

    • Donato Pompo says:

      I don’t know what you mean by “room tiles”.

      If the marble floor is structurally sound you can adhere a ceramic porcelain tile or other types of tile over it. You need to scarify the floor first. If room tiles is some sort of carpet or vinyl tile then you might need to scarify the floor and apply a patching mortar over it to make it a uniform smooth surface.

      If the marble is not structurally sound and well adhered then you should remove it first.

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