What is the right Grout Joint Size?

Although many customers would like a very small grout joint, or if possible, none, grout joints are a necessary part of any tile installation.

New technologies and production methods for tiles have improved and the requirement for larger widths of 5mm-10mm are no longer necessary, however the size of the joint is still dependent on the type of tile chosen.

 Non Rectified Tiles

These tiles are pressed and molded to size before kiln  firing. During this process minor shrinkage can occur to varying degrees from tile to tile so a wider grout line is used to absorb this variance. Most non rectified tiles can be installed between 2.5mm – 5mm.

Rectified Tiles

Are tiles that are cut after production making them, for the most part, identical in size however minor dimensional irregularities still occur so although a narrow joint can be applied, a extremely small joint (1mm – 1.5mm) may not be possible or even ideal.  Many rectified tiles can be installed at 2 – 2.5mm  making them barely noticeable.

Grout joint sizes impacts the aesthetic of the project, slimmer joints are often driving preferences towards rectified tiles to achieve a minimalist look and the perception that smaller grout joints will collect less dirt and require less cleaning.  Using alternatives to a string mop-and-bucket when cleaning can address these concerns. View our tips on how to clean grout.

For large format rectified tiles slim grout lines will deliver the seamless appearance, but how narrow is the grout joint allowed to be? 

The Australian Standard ‘Guide to the Installation of Ceramic Tile’ has no definitive joint size for the installation of porcelain or ceramic tiles.  They provide recommendations as follows:


  • The width of the joint should be wide enough to accommodate the variances in size of the tile as permitted by the manufacturing.
  • Joint widths should be consistent throughout the installation unless otherwise specified.
  • Wider joints may be required to accommodate larger tiles unless otherwise specified.

Other factors affecting grout joint size can include installation pattern and flatness of the substrate. To understand more please view our what you need to know about large format, rectified and non-rectified tiles. 

Despite the limitations of the substrate and the tiles, occasionally and in limited applications, an extremely small grout join can be achieved, however the long-term application may be affected by:

  • Movement in the substrate.
  • Expansion of tiles due to moisture and or temperature.
  • Extremely small joins not allowing for the grout to be fully compacted into the join resulting in grout crumbling and/or coming away.

The size of the grout joint  is determined on inspection of the tiles and substrate with consideration to the above factors for a result to the owners/project managers and the tiler’s professional satisfaction.

This image shows 1mm grout joint attempted for 600 x 600 tile not allowing for dimensional irregularities or future effects from movement, heat or moisture.

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