What Does Movement Joint Mean In Construction?
What Does Movement Joint Mean In Construction?
A movement joint, also known as an expansion joint, is an assembly designed to hold parts together while safely absorbing temperature-induced expansion and contraction of building materials, and vibration, or to allow movement due to ground settlement or seismic activity.
Movement joints are used in a variety of construction projects such as bridges, roads, masonry walls, industrial piping systems, railway engineering, and building construction.
In building construction, an expansion joint is a mid-structure separation designed to relieve stress on building materials caused by building movement induced by thermal expansion and contraction or other factors such as seismic activity.
Expansion joints are used to bridge the gap between two structural elements and restore the building assembly functions while accommodating expected movements. Expansion joints should not coincide with door or window openings but instead should be positioned in sections of full-height masonry.
Movement joints are an important element in various construction practices, allowing for the expansion and contraction of materials due to changes in temperature, moisture, and other factors.
When constructing roads, transverse movement joints can be implemented to prevent potential damage to the concrete slab or surrounding structures by absorbing these forces. Similarly, masonry walls require properly constructed joints that permit calculated degrees of movement without hindering the stability and integrity of the wall.
These joints are usually created by forming gaps in the masonry and filling them with compressible joint fillers, then sealing them with flexible weather-resistant sealants.
To avoid impacting the buttressing provided by return walls, movement joints in masonry walls should not be located at corners unless the masonry is suitably tied. In such cases, it is best to position the joints at least 550 mm away from the internal corner.
Additionally, to prevent issues with door or window openings, it is recommended to position movement joints in sections of full-height masonry. If this is not feasible, an engineer should design the joint to avoid passing around window and door frames.
Bridge construction also utilizes movement joints to accommodate movement in the bridge deck. In railway engineering, jointed track is utilized and consists of rail lengths bolted together using fishplates, with small gaps between rail ends to act as expansion joints in high temperatures.
However, jointed track requires extensive maintenance and does not provide as smooth a ride surface as welded rail, making it less commonly used for high-speed trains.
Overall, movement joints are a critical aspect of construction that must be carefully designed and positioned to prevent potential damage or issues. Understanding their purpose and implementation in various construction practices is essential for successful and safe construction projects.
Movement Joint Installation
Installation of movement joints (expansion joints) is necessary to prevent uncontrollable cracks in tiled surfaces due to temperature changes and other environmental conditions. Movement joints should be incorporated into all external tiled areas and within internal surfaces, where the tiling will come under stress from radiant heat or other sources.
The size and frequency of movement joints should be determined before installation, based on the environmental conditions at the location. Generally, a structural movement joint should be 4x the maximum expected movement, with a minimum width of 10mm.
The width of the joint should also be increased by 1/16″ for every 15°F increase in temperature change above 100°F.
Movement joints should also be placed at perimeters, change of plans, and where tiles are coming up to restraining surfaces. It is important that the width of the movement.
Movement Joint Design Considerations
Design considerations for movement joints (expansion joints) include the size of the gap, the type of system used to fill the gap, and the configuration of the joint.
The size of the gap should be as small as possible to fit the design movement, and the size of the expansion joint system needs to accommodate the full range of expected movements. Expansion joint seals are typically designed to work in tension across the joint width, and oddly shaped expansion joints may include many right angles to fit around corners.
It is important to select a support system that can accommodate building tolerances in all three planes. Expansion joint seals should not be installed to bridge large gaps or over two storeys or more of brickwork below a support system.
Additionally, consideration should be given to reducing centres between movement joints and avoiding compressible fillers that do not fully recover their original thickness.
Expansion Joint Materials
Expansion joints, also known as movement joints, are used to connect two pieces of material such as concrete, metal, or wood in a construction setting. Expansion joints are flexible and allow for movement due to thermal expansion and contraction.
Common materials used for expansion joints include silicone, stainless steel, polymer-based materials, rubber, foam-type materials, compression seal materials, inflated expansion joint materials, strip seals, cork expansion joint materials and plastic joint materials.
Polymer-based materials are reliable for expansion joints because they will not rust and are cost-effective and strong. Rubber is a popular choice for many applications that require expansion due to its flexibility and high strength.
Foam-type expansion joints are composed of cellular fibers securely bonded together and uniformly saturated with asphalt to assure longevity. Compression seal expansion joints are typically classified as neoprene or cellular and installed using a lubricant which also serves as an adhesive.
Inflated expansion joints are cast-in-place systems designed to accommodate movement caused by temperature changes.
Strip seals provide watertight protection against the elements while cork expansion joint material is used when high resiliency is needed such as in sewage plants or floodwalls. Plastic joint materials can be used in various applications including control joints, seismic joints and pressure relief systems.
