Movement joints in construction... doesn’t sound exciting(?!) well these essential components ensure the longevity and integrity of buildings. So let’s explore what movement joints are, why they are needed, and how they might form part of your build project…
What are Movement Joints?
People often view buildings as solid, static objects, but in reality they experience movement, primarily due to environmental factors like temperature and moisture variations. We incorporate joints into the building design, to accommodate this movement.
These joints consist of a gap that allows for expansion and contraction, which is filled with a compressible filler and enclosed with a weatherproof sealant, allowing controlled movement within the structure.
Typically, stainless-steel ties that are 225mm long and spaced 225mm apart vertically, are placed in the middle of the wall to span the joint, transferring out-of-plane shear forces. To let the wall move slightly without causing problems, a debonding sleeve is placed on one side of the joint. This sleeve allows the wall to expand or contract as needed while keeping everything aligned and secure.
How often will you need movement joints?
The frequency of movement joints will depend on the size and design of your building. As an example, for wall panels built using cement mortar, typical recommended joint spacings are:
For Clay bricks - up to 12m centre to centre along a straight length, and 6m from a bonded corner
Concrete blocks - up to 6m centre to centre along a straight length, and 3m from a bonded corner
Recommended spacings are closer together in blockwork panels because the block units are larger in comparison to bricks units, meaning they are more sensitive to movement or volume change.
It’s important to note that the provision of movement joints does not prevent the occurrence of cracks but allows designers to control where and how any crack develops should this occur.
Without properly spaced movement joints, stress can build up, leading to unfettered cracking, warping and structural failure in the walls and adjacent elements. This means your building could suffer significant damage over time, leading to costly repairs and potential safety hazards.
How will movement joints impact the design and appearance of your building?
Properly planned and executed, movement joints can be an unobtrusive component supporting both the functionality and the aesthetics of a building by ensuring that its overall appearance, so far as the masonry structure is concerned, remains intact over time.
Joints are filled externally with a suitably coloured flexible silicone that changes shape as required to hide the joint. This can be specified to closely match your chosen build material. Joints should also be mirrored in internal finishes, which could be more problematic in modern dwellings that feature larger open spaces.
If bed joint reinforcement is used, this incorporation of steel bars or mesh within horizontal mortar joints at key points (such as above and below openings), allows for an increase in the recommended spacing of movement joints: up to 18m centre to centre along a straight length and 9m from a bonded corner for both clay and concrete blocks, creating less joints to disguise.
At WE Consulting Engineers, we understand you want your building to look as good as possible, for as long as possible – give us a call if you’d like more information on movement joints or advice on other structural aspects of your build.
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