Movement joints are often regarded as routine detailing exercises, yet they remain among the most significant factors in preventing cracking and ensuring the long-term performance of masonry. Many defects investigated during expert witness appointments can ultimately be traced back to inadequate provision for movement rather than poor quality alone.
Brickwork is not a static material. Throughout a building’s life, it responds continuously to changes in temperature, moisture content, structural loading, and, in some cases, chemical effects. Bricks undergo irreversible and permanent expansion after leaving the kiln. Expansion can occur for up to 20 years, although it mostly occurs in the first five years. Unlike concrete masonry, which generally experiences drying shrinkage, fired clay brickwork undergoes gradual moisture expansion. Unless this natural movement is anticipated during design, internal stresses accumulate until the masonry relieves itself through cracking.
Understanding Brickwork Movement
The designer’s goal is not to stop movement but to ensure it is accommodated. A skilled designer incorporates movement joints into the façade as an essential design element. When movement joints are poorly placed, they can appear as unattractive scars on the building’s façade.
Movement joints create controlled locations where expansion can occur without damaging the masonry. When properly positioned and detailed, these joints can enhance both structural integrity and appearance.
The amount of movement is influenced by several factors, including:
• Orientation of the elevation; south-facing elevations suffer from greater expansion.
• Brick type and moisture expansion characteristics.
• Temperature fluctuations.
• Building geometry.
• Degree of restraint.
• Panel dimensions.
South-facing elevations often experience greater thermal movement due to greater solar heating, particularly when darker-coloured bricks have been specified. For this reason, the joint frequency may need to be increased beyond standard recommendations.
Joint Spacing Is Only the Starting Point
Guidance commonly recommends vertical movement joints in clay brickwork at approximately 10 to 12-metre centres. However, the appropriate spacing depends on the brick manufacturer’s declared movement characteristics and the degree of restraint within the wall. The first joint should normally be positioned no more than half the normal spacing from corners or returns to avoid stress concentrations.
These values should never be treated as rigid rules. Every building should be assessed individually, taking account of its form, exposure and structural behaviour.
Locations Where Cracking Commonly Develops
Experience shows that cracking frequently develops at predictable locations where restraint is concentrated.
These include:
- Short returns.
- Changes in wall height.
- Junctions between different materials.
- Window and door openings.
- Slender vertical masonry columns meeting horizontal spandrel brickwork.
- Corners of masonry panels.
- Long elevations with insufficient movement joints.
Where returns are particularly short, additional movement accommodation or sliding tie details may be required to prevent stress concentrations from developing. Similarly, transitions between brickwork and alternative façade materials often require careful detailing to allow differential movement.
Bed Joint Reinforcement
Bed joint reinforcement is an effective tool for distributing tensile stresses and reducing localised cracking around openings or areas of stress concentration.
However, reinforcement should never be viewed as a replacement for correctly positioned movement joints. Its purpose is to improve crack control and, in certain circumstances, permit wider joint spacing, normally up to 18m, depending on the design; it will not, however, eliminate the need for movement accommodation.
Horizontal Movement Must Not Be Forgotten
Designers often focus on vertical movement joints while overlooking differential vertical movement.
Where multi-storey masonry is supported at floor levels, horizontal movement joints may be required to accommodate relative movement between structural frames and the external brickwork. Buildings of modest height may not require intermediate support, but taller structures generally benefit from periodic support angles and horizontal joints to relieve accumulated movement.
Primary structures, especially reinforced concrete columns, can compress. In some cases, this has caused a brick façade to act as an unintended load-bearing element, leading to spalling and falling brickwork.
Good Detailing Matters
Even correctly positioned joints can fail if they are poorly detailed.
Successful movement joints require:
• A compressible joint filler.
• A durable, flexible weather seal.
• Appropriate debonded wall ties where required.
• Adequate joint width.
• Continuity through the full thickness and height of the masonry where appropriate.
Attention should also be given to adjacent rainwater pipes, flashings, and other fixtures to ensure they do not inadvertently restrict the intended movement.
Lessons from Forensic Investigations
Having investigated numerous construction disputes over the years, one recurring observation is that movement cracking is often attributed to quality, even when the underlying cause lies in the original design.
Insufficient movement joints, poor joint positioning, inappropriate restraints, or inadequate consideration of differential movement between materials are often the real explanation. Most of these defects could have been avoided through careful detailing at the design stage.
Lime Mortar and Movement Joints
The guidance discussed above primarily applies to modern cement-based mortars. Traditional lime mortars behave differently because they have significantly lower compressive strength and a much lower modulus of elasticity, allowing the masonry to accommodate greater movement through the mortar joints before stresses are transferred to the bricks.
Buildings constructed with lime mortar often require fewer movement joints than equivalent structures built with cement mortars and have demonstrated excellent long-term durability over many centuries. However, movement in lime masonry is more complex and should not be assessed using standard guidance intended for cement mortar construction. The design of movement joints in lime masonry should be determined through a specialised engineering assessment. This assessment must consider factors such as mortar and masonry unit properties, the level of restraint, environmental exposure, and the building’s structural form. Typically, lime mortar performs better in thicker walls than in the standard half-brick stretcher bond used for brick façades.
Final Thoughts
Movement joints are among the simplest and least expensive details incorporated into masonry construction, yet they play a critical role in the long-term durability and appearance of brick buildings.
Good masonry design accepts that movement is inevitable. The challenge is not to resist it but to accommodate it in a controlled and predictable manner.
As buildings become increasingly complex and façade systems combine multiple materials and structural forms, thoughtful movement-joint design remains one of the defining characteristics of successful masonry engineering.
This article is intended to provide general information and insights into prevailing industry practices. It is not intended to constitute, and should not be relied upon as, legal, technical, or professional advice. The content does not replace consultation with a qualified expert or professional regarding the specific facts and circumstances of any particular matter.