TTA Technical & Training Manager Martin Pouncey discusses the significance of movement joints within external tile installations, reflecting the latest guidance available in the British Standards following the 2024 update to BS 5385 Part 3.
For external floor tile installations, movement joints are critical for managing the tile system’s exposure to greater fluctuations of thermal and moisture movement. With the increase in popularity of outdoor living spaces and use of external space as a social gathering area, the need for correct design, construction and installation is essential.
Natural stresses occur in tile systems as a result of movement due to such factors as drying shrinkage, moisture and thermal changes. Stresses can cause loss of adhesion, bulging or cracking of the tiling but they can be localised by incorporating movement joints which should penetrate the full depth of tile, bedding and levelling screed. These work by separating a tiled assembly into smaller, more flexible sections.
In 2024, the guidance provided by BS 5385 Part 3 was updated, covering the design and installation of external ceramic and mosaic, natural stone and terrazzo flooring, and internal agglomerated stone flooring in normal conditions. BS 5385 Part 3: 2024 includes a key statement that for external floor tile installations, intermediate movement joints should be incorporated within the tile assembly at intervals between 3m to 5m. This is an important clarification that reflects how the British Standards continue to progress as industry experience has increased and the market continues to develop. The recommended distance between movement joints depends on the anticipated magnitude of movement, environmental conditions, and the type of tile and substrate used.
Pre-formed intermediate joints support tilers to deliver lasting installations. Perimeter joints are used for separating tiles where they meet at a perimeter, e.g. where the floor meets the wall or where tiling abuts other building structures, such as steps, doors and window frames. Intermediate joints are used to separate continuous tiled areas, dividing a tile system into smaller sections.
Intermediate joints are particularly important in large external spaces such as patios and driveways which are likely to feature a wide surface area. Floor tiles should never be installed with joints between them of less than 3mm and for large format panels, even wider joints are required.
As external tile installations are subjected to significant weathering, it is essential that the water impacting on the surface is adequately managed. Serious consideration must be given to controlling where any water will go and how it will affect the tile, substrate and surroundings.
For all aspects of external tile installations, work should not be carried out unless the temperature is above 5°C and rising. The temperature range for which tiling can be satisfactorily carried out with normal methods and materials is between 5°C to 25°C.
TTA shares free tiling tips in The Tiling Guide, a handbook with practical information on key installation issues available at www.tiles.org.uk/tiling-guide/, and on TTA’s YouTube Channel at www.youtube.com/@TheTileAssociation_.
Further information is available for purchase in TTA’s Technical Publications, free to TTA members. The Tile Association also provides technical support for all member queries related to tile products and installation practices – email technical@tile.org.uk or call 0300 365 8453. Finally, there is a 10% discount available for TTA members on their first year’s subscription to NBS Source.
