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Gauged Porcelain Tile Panels/Slabs installation guidelines


As thin panel installation guidelines continue to evolve and finalize, how would you suggest answering an architect who is asking for guidelines and limitations for installing 6mm over existing tile?

Should we consult with an installation product manufacturer to better understand what they would warranty? In my opinion, this is not a product question but more an installation system question.

As always, any help would be greatly appreciated. 


You are correct. Gauged Porcelain Tile Panels/Slabs (GPTP/S) are an excellent option for tile over tile. Since the existing tile installation will become the substrate for the new GPTP/S it is critical to ensure the existing tile and the layers that support it are carefully analyzed to ensure they support the new installation. Things to check:

– Substructure:

  • Is the substructure designed to support the load of the new installation for its intended use (dead load + live load)?
  • Are structural deflection ratings met?

– Existing tile system layers:

  • What is the existing substrate beneath the tile? Is it properly fastened to the structure?
  • Are there any membranes installed? Are they in good condition?
  • Is the existing tile well bonded to its substrate? Does the bond coat meet tile industry requirements for dry or wet areas? 
  • Soundness of tile system layers can be determined by removing (or core drilling) small sections of the existing tile and substrate. Several areas should be checked.

– Flatness:

  • Is the existing tile installation flat, plumb, true? 
  • Industry standards found in ANSI A108 and A108.19 describe the requirements in detail.

– Movement Accommodation Joints:

  • Were soft/movement/isolation/etc. joints installed as required by ANSI A108, A108.19 and TCNA Handbook Method EJ 171? 
  • Joints will need to be honored through the surface of the new tile installation.

– New installation setting materials/system:

  • I strongly suggest using a system approach from a single setting-material manufacturer. The manufacturer may have a bond-promoting primer that should be applied over the existing tile. 
  • If the existing tile is not flat to meet GPTP installation standards, the manufacturer will have patch or rendering mortar designed to make it flat. 
  • The setting-material manufacturer will have an A118.15LHT thinset for bonding the GPTP/S to the existing tile, and an appropriate grout and/or sealant for the joints between panels and movement joints.

– ANSI A108.19 is the installation standard for GPTP/S: 

  • It describes in detail the requirements for a successful system design and installation. The architect should purchase copy of this document and thoroughly understand it before writing the specification. 
  • Copies can be purchased at: https://tinyurl.com/nhjd9c5k

For floor installations, A108.19 describes two gauge ranges. 3.5-4.9mm and 5.0-6.5mm. The standard does not allow for installed gauge range 3.5-4.9mm on floors. Some manufacturers of GPTP/S may allow for their tile in the thinner gauge range to be installed on floors. Their installation instructions and warranty will take precedence over the standard. 

NTCA Technical Team
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