A guide to grout joint widths and tile installation

grout joints

The gap size between tiles is often referred to as the grout line, grout joint, or grout width, with the size required depending on the type of tile, substrate, grout and your own personal preference as a tiler. These grout lines are designed to prevent water, dust and dirt from accumulating in the inevitable gaps between tiles, whilst also ensuring the tiles are able to withstand movement, thermal expansion and variations within the tiles.

The common practice is a gap of 2mm or 3mm for wall tiles and between 3mm and 5mm for floor tiles, however it is important to follow the standards within the BS 5385-1 which outline the sizes required depending on the tiles being used and the substrate. The grout joint is not purely an aesthetic feature, it provides an important technical function.

Instructions for installing the correct grout widths:

  1. The substrate must be dry, clean, and flat, as a tiled surface will only be as good as the surface below it.
  2. Before beginning tiling it is advisable to complete a trial run of the tile layout, with the tiles and required spacers used to help visualise the final design.
  3. Use a laser level or chalk line to mark a straight reference point and lay the first tile in-line with this mark. The adhesive used should be selected based on the surface and the type of tile being used, with a variety of products available to suit every project.
  4. Use tile spacers to create the required grout width between the first and second tile, with at least 2 spacers used per tile side. If a levelling system is used, such as the LevTec system, additional spacers may be required to create the ideal grout width, whilst still avoiding lippage.
  5. Butt the second tile against the spacers of the first tile, then add more spacers ready for the next tile. Continue to repeat this process, with spacers used to establish an accurate grout width across the entire tiled area.
  6. It is important to include expansion joints, otherwise known as movement joints, in large tiling projects, as these are designed to create space for slight movements within a tiled surface. These joints should be installed around the perimeter and at distances of between 5-8m across the surface.
  7. When the tiles have set after between 20-30 minutes, remove the spacers before the adhesive fully dries. This time can vary between adhesive manufacturers, so you will need to check labels to find out accurate drying times.

Important points to note:

  1. If rectified tiles are used, a standard grout width of 2mm or 3mm can be used along each tile edge to create a professional and seamless finish. However, non-rectified tiles often require larger widths of between 3-5mm to allow for possible variations in the tile dimensions.
  2. Tiles which are installed above wooden substrates are often prone to movement, which can be minimised through effective grout line widths. By ensuring the correct grout line gaps are used, potential cracking, chipping and de-bonding can be prevented. In addition, flexible grout should be used, as it can help to absorb any movement.
  3. The facial area of tiles also has a bearing on the required grout width, with smaller tiles measuring less 1m2, or where one side is less than or equal to 600mm in length, required to have a minimum grout width of 2mm. For larger tiles measuring up to 1200mm in length, a grout width of at least 3mm is required. Any tiles larger than this must have a grout joint of 5mm.
  4. Tiling directly onto plywood is no longer recommend as a suitable substrate, instead, a specially developed tile backer board should be used. These boards provide a stable and moisture resistant surface, with the additional benefit of being more environmentally friendly.

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