There are many types of movement within a tiling installation that occur due to dimensional changes in response to environmental conditions. Stresses causing movement can induce bulging, cracking and loss of adhesion. To avoid these failures, consideration during the setting out of a tiling installation should be made. Placement of movement joints to relieve the tension and reinforcing the substrate and making non compressible, is essential to successful tiling.
TYPES OF MOVEMENT
• Drying Shrinkage Movement
- The shrinkage of the base and/or screed can continue for some years after the tiling installation which can result in the build-up of lateral stresses within the tiling layer. Consider uncoupling with BAL FLEXBONE 2EASY.
• Moisture Movement (wetting and drying)
- Can occur when new bases and/or screeds are covered over with final floor finish before most of the drying/shrinkage has taken place. Consider BAL NEW FLOOR or BAL FLEXBONE 2EASY when needing to fast-track installation.
• Thermal Movement
- Ares of intense direct sunlight e.g. sunrooms, conservatories, dark coloured tiles externally etc, can heat up and cool very quickly whilst the background may not. Consider uncoupling with BAL RAPID MAT (internal only).
• Vibration, impact and thermal shock
- Can produce early failure. All areas for tiling need to be flat and even, deflection free, and tiles solidly bedded to limit these types of movement.
Movement joints are not to be confused with structural movement joints. Incorporate movement joints in appropriate positions when setting out the tiling. (see BS 5385-1:2018 and BS 5385-3:2014).
Location of movement joints.
Movement joints are required in the following areas:
• Over existing and/or structural movement joints
• Where tiling abuts other materials
• Junctions between different background materials
• Perimeter expansion movement joints
• Intermediate expansion movement joints – Should extend through substrate
Where a movement joint is required within the tiling layer and its bed, the movement joint should be a minimum of 6mm wide.
All joints should be rectangular in design with straight smooth edges. Width:depth ratio of the selected sealant should be installed following the manufacturer’s recommendations. Ensure joint spaces are free from other materials and dry, and that any joints awaiting sealing are kept clean.
Where flexible joints are selected, the sealant used should be specifically suitable for use in the normal service conditions of the application in accordance with BS 6213.
STRUCTURAL MOVEMENT JOINTS
Flexible joints aligned to structural movement joints see below taken from BS5385-3:2014
Flexible joints should be used at floor perimeters and to divide the floor into bays. Where possible, they should coincide with structural features e.g. door openings, columns, or they can be planned to provide a decorative effect.
In floors that must withstand hard-rimmed wheel traffic or the dragging of heavy loads, the movement joints should have edges reinforced with metal or rigid plastic.
Such movement can be significant in new constructions whilst the moisture content is still high. Covering over with a tiling layer before the drying and shrinkage has taken place can lead to failures. Where moisture is present in a background, soluble salts can migrate and result in adhesion failure. Adequate preparation of the background using damp-proofing, waterproofing and priming is required. By following recommended mixing, installation, drying/curing and cleaning recommendations as directed by the manufacturers, failures relating to moisture can be avoided.
Changes in temperature cause thermal expansion and contraction (linear). With regards to tiling, linear expansion when not addressed with correct movement joints will cause failures. Factors to consider are underfloor heating and cooling systems, areas of direct sunlight, areas of significant temperature fluctuation e.g. sunrooms, atria, and dark coloured tiling externally. Movement joints within the substrate are crucial as the tiling layer and substrate will heat/cool expand/contract at different rates. The use of an anti-fracture uncoupling system e.g. BAL RAPID MAT should be considered.
SILICONE MOVEMENT JOINTS / SEALANTS
When selecting a sealant, consideration of the service conditions of the environment it is to be installed into and capability of accommodating the anticipated amount of movement, must be made. The sealant should be installed following the manufacturer’s recommendations.
When using a silicone as a movement joint, care should be taken so that the sealant can move freely as the joint moves, the sealant should adhere to the two principle surfaces only. If the sealant is bonded to a third surface, it will most likely cause failure of the movement joint. A bond breaker (polyethylene tape or film to which the sealant will not stick) should be used to prevent adhesion to the third surface (BS 5385-1:2018).
MOVEMENT JOINTS IN SCREEDS
Wherever possible movement joints or day joints in the screed should be formed as straight joints. Where a joint intersects with other movement joint, these should be placed at right angles. Where there are movement joints in the substrate, a movement joints should be incorporated in the tiles adhesive bed to match.
MOVEMENT JOINTS ABOVE 3m HEIGHTS
BS 5385-2:2015 10.3 “Storey heights horizontally and approximately 3 m to 4.5 m apart vertically; ideally, they should be located over movement joints in the structural background and at structural material changes; for example, horizontal joint at top and bottom of floor slab, vertical joint at internal corners and at junctions with columns.”
TECHNICAL ADVISORY SERVICE
For free expert guidance on the use of BAL products, or any aspect of ceramic tiling with BAL products, contact the BAL TECHNICAL ADVISORY SERVICE on 01782 591120.
THE BAL 25 YEAR GUARANTEE
BAL products are supplied with a 25 year product guarantee. For further details and/or copies please contact the Company’s marketing department.
The customer must verify the suitability of any information, opinion, recommendation or advice (“information”) provided by the Company for the particular application for which any goods are intended to be used and the Company accepts no liability (whether in contract, tort or otherwise) whatsoever for any loss, damage or expense arising from the misuse of any information it supplies, nor for the use of any information in or for applications which are unsuitable or inappropriate. Building Adhesives Ltd operates a continuous research and development programme and reserves the right to alter or to update information from time to time.
“Note: Any advice, opinion or information is given to assist the use of the Company’s products on the basis that the user will ensure its suitability for the application intended. In particular the Company cannot accept liability for loss or damage which may arise from incorrect use of its products or from poor workmanship. The Company operates a continuous research and development programme and reserves the right to update information without notice.”
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- TN 02.23 Tiling to Asphalt Floors
- TN 03.23 - Use of Primers and Bonding Agents
- TN 04.23 - Ceramic & Natural Stone Floor Tiling to Heated Sub-floors
- TN 05.23 Tiling A Small External Patio & Ground Floor Terrace
- TN 06.23 Common Issues With Grouting
- TN 07.23 Deflection of Sub-Floors and Rigid Finish
- TN 08.23 Screed Drying Times
- TN 09.23 Types of Movement in Tiling Installations
- TN 10.23 - Heavily Trafficked Floors & Hard Wheeled Traffic