Design in movement joints and profiles to protect the design

Take a quick look at your surroundings.  If you are sitting near a tile or stone installation have you noticed a movement joint?

So often movement joints go totally unnoticed, despite the concern from architects and designers that they look unsightly.  However, excluding them is a risk, since they play a pivotal role in tile or natural stone installations.  The best way of preventing cracks in tile and stone is to use a complete system-solution with Schlüter-Dilex movement joints and Schlüter-Ditra 25 uncoupling membrane.

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As a worldwide leading product for over 25 years, Schlüter-Ditra 25 is the unsurpassed uncoupling membrane for tile and natural stone installations. When combined with Schlüter-Dilex movement joints, it is the essential and first choice for securing floor coverings for many architects and specifiers looking for a lasting, reliable solution.

The geometry of the patented Schlüter-Ditra 25 allows for the absorption of lateral movement in each direction.  Through its unique two-layer design, Schlüter-Ditra 25 truly separates the substrate and tile or stone covering by creating essential free space between the layers in which the matting can move safely, reacting to the movement of the substrate and surface, independently of each other.

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By their very nature, single part and three part mats cannot function in the same way due to the fact that they rely on a direct bond with the screed and surface covering. By definition, these products fail to separate and rely in some instances, on the debonding of layers to cope with movement, leading to long term issues with loose tiles, weakened grout joints and ultimately a cracked surface covering.

 

Fluctuations in temperature and moisture cause movement in the subfloor and lead to cracks transferring to the tile or stone covering, or worse, cause a loss of bond between the covering and the substrate, which can result in overall damage to the surface covering.  For this reason, industry standards state that all tile and stone installations should include the use of movement joints.

A lack of movement joints can be a contributing factor to many different types of failure.  Furthermore, if the architect does not include movement joints in the specification, liability for any resulting problems could fall to them. Even if the problem doesn’t directly relate to a lack of movement joints, it is the architect’s responsibility to specify the type of joint and their location.

In addition, that is why uncoupling membranes and movement joints need to be considered at the specification stage.  In addition, if included at specification, movement joints can be incorporated into the design seamlessly, with a whole host of colours and finishes available to match the overall scheme.

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There are two key questions that an architect or specifier needs to know the answer to:

1. What type of movement joint do I need to specify? 2. Where do I place them?

To answer the first question, it helps to understand the types of movement that can occur. Typically this includes:

  • Drying shrinkage: contraction and shrinking causing an increase in tensile stress
  • Differential movement: different parts of the structure moving at different rates
  • Deflection movement: the degree of movement when a structural element is placed under a load
  • Structural movement: occurs frequently within buildings and can include expansion and contraction of the structure materials due to subsidence, settlement or sway, etc.
  • Moisture movement: moisture enters buildings through porous surfaces as liquid or as vapour causing movement
  • Thermal movement: changes in the shape, area and/or volume of materials due to temperature changes and fluctuations

Each of the above influences the stress on the structure leading to movement in the material surfaces and substrates.  There are areas within the design of a building that are commonly subject to stress due to the above types of movement.

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Structural joints
Structural joints (otherwise known as expansion joints) are joints required for static or engineering reasons, which divide a building in to various movement segments. They should run through all load bearing and non-load bearing parts of a building and must be continued in the screed construction and the floor covering at the identical location and in the specified width.

Example Structural Joints to Specify:
Schlüter-Dilex-BT is a structural expansion joint made of aluminium with lateral joint connections to a sliding telescopic centre section.  This allows for absorption of three-dimensional movement.

Schlüter-Dilex-KSBT is a structural movement profile with edge protection, consisting of side anchoring legs of aluminium or stainless steel connected to a 20 mm or 30mm wide movement zone of soft synthetic rubber.

Intermediate joint profiles in screeds
Intermediate joints create a pattern of limited fields in large areas of screed and covering. They must be continued from the surface of the covering to the separating layer under the screed or to the covering of the insulation or waterproofing layer. In door transition areas, the screed should contain movement joints, which are continued in the covering to reduce stresses occurring at these locations and to prevent the transmission of impact sound. Movement joints in the substrate may not be closed or covered with flooring materials.

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Example Screed Movement Joints to Specify:
Schlüter-Dilex-DFP is a movement joint profile to be installed at door areas or used to divide screed areas.

Schlüter-Dilex-EP is a movement joint profile for application in floating or bonded screeds. The side sections consist of rigid, recycled plastic, connected on the top and bottom with soft, grey CPE movement zones.

Example Intermediate Joints to Specify for the Tile Covering:
Schlüter-Dilex-KS is a movement profile with edge protection consisting of lateral anchoring legs made of aluminium or stainless steel, which are connected to a replaceable movement zone made of soft rubber.

Schlüter-Dilex-BWS is a movement joint profile with side sections of rigid, recycled plastic. The movement zone consists of soft CPE and creates the 5 mm wide visual surface.

Perimeter joints
Perimeter joints are movement joints placed in the screed and the covering along walls and construction elements that penetrate the screed, such as columns.  They reduce impact sound transmission and absorb the movements of the floor assembly.

Edge joints may not be rigidly closed, since this may lead to the formation of sound bridges and tensions in the covering construction.

Our range of movement joints includes cove-shaped profiles for wall-to-floor transitions and inside wall corners and they are designed to allow for especially easy cleaning.

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Example Perimeter Joints to Specify:
Schlüter-Dilex-KSA is a connection profile with edge protection. The profile’s anchoring legs, made of aluminium or stainless steel, are connected to a replaceable movement zone made of soft PVC. The profile is used for creating transitions between coverings and fixed structures such as window frames.

Schlüter-Dilex-HKS is a cove shaped, stainless steel profile with a maintenance free movement zone for floor to wall connections in ceramic tile or natural stone coverings.

Connection joints
Connection joints are movement joints placed in the screed and the covering at construction elements such as window openings, doorframes, shower trays and bath tubs.

Example Connection Joints to Specify within the Tile Covering:

Schlüter-Dilex-BWA provides a flexible connection between tile or stone surfaces and existing coverings or structures, such as door and window frames.

Schlüter-Dilex-AS is a joining profile for creating flexible joints to fixtures such as shower trays, baths, door and window frames.

How should movement joints be placed to ensure a lasting installation?
The answer is to create tile or stone ‘fields’ large enough to absorb the anticipated movement between the substrate and the tile or stone covering. Movement joints must be installed in certain locations and positions to prevent tiles, stone or grout from cracking or prevent the tiles from tenting and becoming debonded from the substrate.

However, ensuring movement joints are placed in the exact location of movement joints is imperative because if they are in the wrong place they won’t successfully protect the installation.

Industry guidelines for unheated screeds suggest that the maximum tile or stone field should be no more than ten metres in each direction but in practice, depending on the individual applications, it tends to be between five and eight metres.

British Standards (BSI) 5385 covers the requirements and methods for movement joint applications. Part 3: 1989-Section 3 – 19.1.1 states that the building designer should assess the magnitude of any potential stresses and decide where movement joints should be located, considering all relevant factors, including the type of flooring, bed and substrate.

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The Formula
A circle provides the best configuration for movement joints, because the forces from the centre are equal in each direction.  However, in practice hardly any floors are circular, so it is best to look at square and rectangular floors. In a square configuration, the ideal field size is where the ratio of the shortest to the longest distance from the centre of the force is approximately 1:1.5.  Generally, the tile or stone field should be kept as square as possible, and where underfloor heating is present, the field should not exceed 40 sq. metres.

However, most floors tend to be rectangular, rather than square and rectangular shapes are not usually the best configuration, as the ratio of the shortest to the longest distance exceeds 1:1.5.

On suspended floors, stress-relieving joints should be inserted where flexing is likely to occur, for instance, over supporting walls or beams. Movement joints must carry through and be situated directly over any joints in the substrate, and at any changes in the substrate, such as timber to screed, or new to old screed, and heated to unheated are some examples.

In areas less than two metres wide perimeter joints are not normally required, unless conditions generate stresses which are likely to become extreme, for example temperature changes.

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A decorative finish
As we have discussed above, the movement, expansion, and control joint profiles of the Schlüter-Dilex series offer a maintenance-free and functional solution, controlling movement in the screed or substrate joints and transferring through to the surface when installed in line with British Standards, BS5385 parts 3 and 4 for tile, and part 5 for stone.

None the less, movement joints aren’t the only profile consideration that should be incorporated at the specification stage of planning.  The difference between something good and something great is attention to detail.  When careful consideration has been made to the sanitaryware, taps, shower, lighting and the tile or stone covering in a kitchen or bathroom, why leave the choice of finishing profiles to the installers, or worse, leave exposed tile edges, when a palette of designs and hundreds of options for finishes, textures, materials and colours, are available with Schlüter-Profiles.  The full range offers an ideal combination of functionality and design solutions, suitable for both residential and commercial projects.

Recently introduced to the profiles range, Schlüter-Trendline is a selection of textured finishes applied to the Schlüter-Quadec, -Rondec and -Jolly profile families. There are a variety of on-trend textured colours available to complement tile or stone in greige and concrete with beiges and greys right through to rustic-brown for wood and graphite metal finishes.

Also, the Schlüter-Designbase-SL decorative skirting range has been expanded, offering an option to include a channel to run cables through. Schlüter-Designbase-CQ allows cables to be hidden, and is available in matt white anodised and stainless steel effect aluminium finishes for a sleek alternative to skirting boards. Also in the range is Schlüter-Designbase-QD an option when combined with Schlüter-Liprotec LED strips, provides skirting light, and can also be used for borders within a wall.

Edge Profiles for Floors: Schlüter-Schiene, the original finishing threshold strip (otherwise known as diminishing profiles), finishes tiled surfaces and protects the outer edges of ceramic and natural stone floor coverings. The threshold of the Schlüter-Reno series create a smooth transition between adjoining floor coverings of different heights, protecting the exposed tile or stone edge.

Wall Corners and Edge Profiles: The profiles of the series, Schlüter-Jolly, Schlüter-Rondec, and Schlüter-Quadec create a highly durable and decorative finish for wall coverings and skirtings made of tile and natural stone.  Designer accents can be created using the range of profiles in conjunction with the decorative Schlüter-Designline and Schlüter-Quadec-FS border profiles.

Stair Nosing Profiles: The edges of stairs are exposed to heavy mechanical stresses and represent a high risk for injuries. Because of their slip-resistant design and excellent visibility, Schlüter-Trep profiles improve safety and offer DDA compliance and protection. They can also be combined with Schlüter-Liprotec illuminated profiles to add decorative visuals for unique designs on stairs, steps and plinth edges.

Learn More about specifying for crack-free tile and stone
Host the RIBA approved
CPD seminar Movement Joints and Uncoupling Membranes for Tile and Stone Coverings to gain the knowledge and confidence in specifying appropriate movement joints and uncoupling membranes to counteract stresses in the substrate such as drying shrinkage, deflection and thermal movement to prevent cracked tiles, stone and joints etc.

Contact us to book a CPD Seminar.
T: 01530 813396  E: training@schluter.co.uk or visit our website www.trainedwithschluter.co.uk.

Schlüter-Systems have dedicated consultants on hand to help with any stage of your specification project. For more information.
T: 01530 813396 E: pr@schluter.co.uk  or visit www.schluter.co.uk.

NBS Clauses and BIM Objects for Schlüter-Systems Ltd are available on NBS Plus, National BIM Library and at www.schluter.co.uk.