What kind of thinset would you recommend for Porcelain Tile. (non porous)


Bond Failure - a local contractor installed on the floor of my residence in San Diego a porcelain large size tile manufactured in Spain. He used a custom Building thinset mortar premium for Marble and Stone, from Home depot The whole job needs to be reinstalled as there was no adhesion between the tile and the thinset. The base floor is wood and has been reinforced prior to installation. The wood floor has been recover by hardibacker boards. What kind of thinset would you recommend for Porcelain Tile. (non porous)


ANSWER - Porcelain Tile should be installed with a latex modified thin-set or a polymer modified thin-set. The Custom Marble Granite Mortar I believe is a polymer modified thin-set. For larger tiles 12x12 or larger should use a 1/4" sq. notch trowel. Use flat side of trowel to spread first on subfloor then trowel with notch side in one direction "Only" then set tile into thin-set and move in a perpendicular direction to the trowel marks and push down to embed tile. Don't trowel too far ahead and make sure thin-set stays tacky.

If the thin-set did not bond to the tile, then either the thin-set dried too quickly or installer waited too long before embedding the tile into the thin-set, relative to temperature and absroption rate of Hardibacker board, and it skinned over and lost bond. Good Luck!

13 thoughts on “What kind of thinset would you recommend for Porcelain Tile. (non porous)

    • Donato Pompo says:

      It depends on whether you are installing on a floor for foot traffic or otherwise or on walls. It also depends on what substrate you are bonding to. There are organic mastics that are premixed or polyurethane adhesives. For bonding to concrete or cementitous materials it is best to use an appropriate ANSI A118.15 thin-set mortar for the best performance. It is important to follow the manufacturer’s directions.

  1. STACI M BAKER says:

    Hi, is there a pre-mixed thinset I can use with porcelain 6 X 24 inch tile?

    Also I am tiling every room in my house with a wood look porcelain tile except bathrooms & kitchen. We have half the house completed & I have just recently read somewhere that porcelain wood look tile peels? Is this true, if so is there any way to prevent this?

    Thank you,

    • Donato Pompo says:

      I answered your thin-set question above.

      I have heard and seen evidence where an ink jet wood tile had spots that looked like it pealed, but we have not had the opportunity to fully investigate it. I have asked a major manufacturer of these tiles and he claims that is not an issue with their product and was not aware of it occurring with other products. There are plenty of successful installations of this type of tile where there is no indication that it peals.

      • STACI BAKER says:

        Thank you so much! For answering both questions. The first time I posted only the first question & I did not think it sent. While I was looking for proof it was sent I came across someone asking about porcelain pealing so I added it & resent.

  2. Nick Basilotto says:

    Hi Donato, I have about 1000 sq ft of floor tile to install, they are 9 x 48 “pressed not rectified” porcelain wood plank tiles. I would very much like to use a premix thin set with a modified polymer additive already mix it in, is there such a thin set? Which one do you recommend? I don’t understand why most tile installers say “NO” to premix when it already has the proper consistency and it would save time. Slump should be better controlled with a consistent mix, IMO.

    • Donato Pompo says:

      The premixed thinset is misleading advertising. It is actually an ANSI A136.1 mastic adhesive that has been around for years. It has been used a lot for wall applications for commercial work that is likely to be remodeled within 10 years.

      It is not a long lasting product. It has lots of limitations in how it can be used and for what applications; particularly for floor applications. The mastic bond strength is significantly less than the ANSI A118 thinset mortars. Most industry installation details do not recommend it for the adhesive.

        • Donato Pompo says:

          I am not a fan of Schluter Ditra uncoupling membranes unless you have a substrate with a lot of cracks. Depending on the type of installation, I think that Schluter requires that you use their thinset mortar in order for it to be warranted.

          Mapei Ultraflex 1 does meet ANSI A118.4 for a polymer modified thinset mortar. It is not one of their better thinsets, but it is recommended for bonding porcelain tile.

  3. harry plamer says:

    Hello, do you have a recommendation for the installation of 2′ x 2′ porcelain tile on a new concrete floor? This is exterior and open to the elements if you could also name a grout for the same application that would be nice too.

    • Donato Pompo says:

      Normally exterior floor applications on pool decks and patios tend to have problems if they are not installed correctly.

      First of all, you shouldn’t install tile over concrete younger than 28 days. There are exceptions if you use special installation products.

      2nd, make sure you have a drainage plan in place. Determine where is the water going to go and how do you evacuate it into the drains.. You can slope towards a planter or lawn if there is a way for the water to drain from those areas. You can install trench drains so they are inline of a uniform slope. You can install area drains where the tile has to slope from all directions to that drain. This is problematic for a large 2′ x 2′ tile as you will have to cut the tile down in order to accommodate the slope.

      The concrete slabs are normally not perfectly sloped or perfectly flat within that slope plane. So you need to adjust the slab so you ideally have a slope of 1/4″ per foot. You might have to install a mortar bed either a bonded mortar bed or a non-bonded mortar bed to establish the slope.

      At this point you should establish where are your movement joints going. Movement joints mitigate the expected expansion and contraction of the tiles.
      Any control joints in the concrete technically need to be honored and extend up through the tile assembly. There are exceptions if they are not structural joints and you use a crack isolation membrane. For exterior applications movement joints should be placed every 8 to 12 feet in each direction, at all perimeters at restraining surfaces, and at any change of planes or materials. You should use a closed-cell foam backer rod or tape, and install the joints with an ASTM C920 traffic grade sealant that can be a silicone or a polyurethane.

      To avoid or minimize efflorescence staining that is common in exterior decks, you should apply a waterproof/crack isolation membrane. Once you have the established slope then you apply the preferable liquid applied waterproof tile membrane where you paint on two coats of it per the manufacturer’s directions.

      Once the membrane is cured you can adhere the tile directly to the membrane. You should use a polymer modified thinset mortar that meets at a minimum ANSI A118.4 or better yet that meets ANSI A118.15. The thinset mortar adhesive has to be applied in a manner where the thinset has 95% contact between the back of the tile and the membrane. All edges and corners of the tile have to be fully supported with the thinset mortar. There can’t be any voids larger than 2 square inches (size of a golf ball). This is a critical step for large tiles if you don’t apply the thinset properly to make good contact and to avoid voids.

      The thinset mortar should be forcibly applied to the back of the tile and the membrane with the flat side of a notched trowel. This is to ensure good contact. Then the installer applies more thinset with the noticed side of the trowel, which for a large tile should be at least a 1/2″ notched trowel. The trowel ridges should be applied parallel to one side of the tile; if necessary it can be applied to the membrane too, but the trowel ridges on the back of the tile have to line up with the ridges on the membrane in the same direction. The tile is then beat into place and shifted perpendicular to the trowel ridges so the trowel ridges collapse into the trowel valleys. As the tile is being installed it should be removed to verify they achieved with thinset contact and then immediately replaced with any added thinset to fill any voids.

      Regarding what grout to use, you should use an improved cementitious grout that meets ANSI A118.7.

      There are several major manufacturers of tile installation products. All of the installation products from mortar bed to grout should be manufactured by the same company to ensure compatibility and to get an extended warranty. This is called Single Source Responsibility. This way if there is a problem you are only dealing with one company and not several companies all pointing their fingers at each other.

      These companies offer 10 year or 15 year or 25 year Labor and Material Warranties that covers full replacement cost if their products fail if you use a certain combination of products that are higher quality products. This isn’t no-fault insurance. The warranty is based on the installer following industry standards and the manufacturer’s directions. So you have ensure that the installer guarantees that they will do so. Often they don’t, so you have to have a quality control plan and oversight to keep them honest.

  4. Sammy says:


    I am installing 12×12 porcelain non-rectified on a concrete floor for basement kitchen. Do you know what brand and model is the best mortar I can use?
    Also, do I need to apply primer to the concrete floor first?

    • Donato Pompo says:

      For a porcelain tile you have to use either an ANSI A118.4 or A118.15 polymer modified thinset mortar for bonding to a concrete floor. There 4 key manufactures of thinset mortars who make a variety of these products such as Custom Building Products, Laticrete International, Mapei, and TEC. There are some others.

      You don’t need a primer to apply to the concrete floor, but you do need to make sure there are not contaminates on the floor and the water readily absorbs into its surface. It can’t be too smooth and should have at least CSP 2 finish. It may be necessary to scarify the floor first. Of course the floor also needs to be flat without out-of-plane irregularities.

Leave a Reply

Your email address will not be published. Required fields are marked *