1. Introduction
Movement joints are a critical component of commercial buildings and multi-storey car parks. Large commercial structures are generally constructed from concrete, steel, masonry and other materials that are subject to movement throughout their service life.
Temperature changes, concrete drying shrinkage, moisture movement, structural loading, creep, deflection and differential movement between structural elements can all generate stresses within a building.
In a multi-storey car park, these effects can be particularly significant because the structure typically incorporates large concrete slabs, beams, columns, ramps, exposed façades and extensive areas of waterproofed deck. The structure is also subjected to repeated vehicle loading, vibration and environmental exposure.
Movement joints provide controlled locations where these movements can occur. They help prevent uncontrolled cracking and protect the structural, waterproofing and architectural components of the building.
The Concrete Centre identifies movement, drainage and waterproofing as important considerations in the design and detailing of multi-storey concrete car parks.
2. What Is a Movement Joint?
A movement joint is a deliberately formed separation between sections of a building or structural element that allows controlled relative movement.
The joint is designed so that adjoining sections can expand, contract, deflect or move without transferring excessive stress into the surrounding construction.
Movement joints may be incorporated into:
- Concrete floor slabs
- Parking decks
- Ramps
- Beams and structural frames
- External masonry walls
- Façades
- Parapets
- Concrete walls
- Pedestrian walkways
- Podium decks
- Roofs and terraces
- Waterproofing systems
- Areas where different structural elements meet
The joint normally incorporates a suitable flexible or compressible material. In waterproofed areas, a joint system may also include a waterproofing seal, flexible membrane detail or proprietary movement-joint assembly.
The exact construction depends on the location, expected movement, structural requirements, exposure conditions and waterproofing requirements.
3. Why Are Movement Joints Necessary in Commercial Buildings?
Commercial buildings are often considerably larger than residential buildings. Long elevations, large floor plates and extensive structural frames create greater opportunities for movement.
Concrete is particularly affected by drying shrinkage, creep and temperature changes. External walls and façades are also affected by solar heating and changes in moisture.
Movement can therefore occur as a result of:
- Thermal expansion and contraction
- Concrete drying shrinkage
- Moisture movement
- Creep
- Structural deflection
- Differential settlement
- Wind loading
- Changes in imposed loading
- Differential movement between materials
- Construction sequence
- Long-term environmental exposure
For masonry walls, NHBC guidance recognises expansion, contraction and moisture-related volume changes as causes of movement and recommends appropriately positioned joints to control cracking.
In a large commercial building, movement joints divide the structure or its finishes into manageable sections and reduce the accumulation of movement-related stresses.
4. Movement Joints in Multi-Storey Car Parks
Movement joints are particularly important in multi-storey car parks because of the size and exposure of the structural frame.
A typical multi-storey car park may contain:
- Large reinforced-concrete floor slabs
- Long-span beams
- Columns
- Ramps
- External decks
- Parapets
- Stair cores
- Expansion zones
- Waterproofing systems
- Drainage channels
- Movement joints between structural sections
The Concrete Centre notes that concrete buildings must be designed to accommodate movements arising from early-age contraction, creep, drying shrinkage and temperature effects, and specifically uses multi-storey car parks as an example when considering movement in concrete structures.
Without appropriate movement provision, stresses can result in cracking of concrete decks, damage to waterproofing systems and deterioration of structural components.
5. Movement Joints in Car Park Decks
Movement joints within parking decks are designed to accommodate relative movement between sections of the structure.
These joints are particularly important where the car park is divided into structural bays or separate sections.
The joint must accommodate movement while remaining capable of resisting the environmental conditions experienced within the car park.
A failed deck movement joint can allow water and contaminants to penetrate into the structure.
This is particularly significant in exposed car parks because rainwater may carry chlorides and other contaminants onto the concrete surface. In colder climates, de-icing salts can increase the chloride exposure of reinforced concrete.
If water and chlorides reach reinforcement, corrosion can develop. Corrosion can cause expansion of the reinforcement, cracking and spalling of the surrounding concrete.
Consequently, maintaining the integrity of movement joints is an important part of maintaining the durability of a reinforced-concrete car park.
6. Movement Joints and Waterproofing
One of the most important functions of a movement joint in a commercial building or car park is maintaining waterproofing continuity.
A movement joint cannot simply be filled with a rigid material because the joint needs to remain capable of moving.
A suitable movement-joint system may incorporate:
- Compressible joint filler
- Flexible sealant
- Waterproofing membrane
- Joint nosing
- Reinforcement or edge protection
- Drainage components
- Proprietary movement-joint assemblies
The joint must be detailed so that movement can occur without opening a pathway for water.
In a car park, this is especially important at:
- Parking deck joints
- Ramp joints
- Drainage channels
- Upstands
- Parapets
- Podium interfaces
- Areas between separate structural blocks
- Interfaces between existing and new construction
The waterproofing system must be compatible with the movement-joint detail. A membrane that is rigidly bridged across a moving joint can crack or debond when the structure moves.
7. How Movement Joints Protect Commercial Buildings
Movement joints provide several important forms of protection.
Structural Protection
They help control stresses caused by thermal movement, shrinkage, creep and other forms of movement.
Crack Control
They provide planned locations for movement, reducing the likelihood of uncontrolled cracking elsewhere.
Waterproofing Protection
Correctly detailed joints help maintain the waterproof envelope of roofs, decks, podiums and car parks.
Durability
Preventing water penetration helps reduce the risk of deterioration to concrete, reinforcement, finishes and internal areas.
Protection of Finishes
Movement joints prevent rigid finishes such as render, tiles and coatings from being forced to accommodate excessive movement.
Reduced Maintenance
Controlling movement can reduce recurring cracking and associated repair costs.
8. Movement Joints in Commercial Building Façades
Commercial façades can be particularly susceptible to thermal movement because of their large surface areas and exposure to sunlight.
Masonry, concrete panels, curtain walling, cladding and other façade materials can respond differently to temperature and moisture.
Where different materials meet, differential movement can occur.
Movement joints may therefore be required at:
- Long elevations
- Changes in building geometry
- Structural movement zones
- Interfaces between materials
- Corners and returns
- Changes in wall construction
- Around certain openings
- Parapets
- Interfaces with structural frames
For masonry, the location and spacing of movement joints should be established by the design rather than selected solely on the basis of a generic spacing rule. NHBC guidance highlights the influence of wall length, geometry, openings, restraint, orientation and masonry type on movement and joint positioning.
9. Movement Joints and Ramps
Car park ramps are particularly important because they combine structural movement with vehicle traffic.
The joint system must withstand:
- Repeated vehicle loading
- Tyre impact
- Braking forces
- Vibration
- Water exposure
- Temperature variation
- Cleaning activities
- De-icing materials where used
A poorly installed or deteriorated ramp joint can become damaged by vehicle traffic.
Defective joints may result in:
- Cracked concrete
- Damaged joint edges
- Loose joint materials
- Water penetration
- Noise and vibration
- Trip hazards
- Damage to waterproofing
- Further deterioration of surrounding concrete
For this reason, movement joints in heavily trafficked areas should be designed and installed specifically for the anticipated traffic conditions.
10. Common Movement-Joint Defects
During condition surveys of commercial buildings and multi-storey car parks, the following defects should be recorded:
- Cracked sealant
- Split sealant
- Debonded sealant
- Missing sealant
- Hardened sealant
- Joint filler deterioration
- Open joints
- Joint edge spalling
- Cracked concrete adjacent to the joint
- Water staining
- Active water leakage
- Corrosion of exposed metal components
- Failed waterproofing
- Debris within the joint
- Mortar or concrete bridging
- Rigid coatings bridging the joint
- Damaged joint nosings
- Loose or displaced joint components
- Differential levels across the joint
The condition of the surrounding structure should also be examined because movement-joint deterioration can be accompanied by cracking or concrete deterioration.
11. Inspection of Movement Joints
Movement joints should form part of the planned inspection regime for commercial buildings and car parks.
A visual inspection should consider:
Joint condition: Is the joint continuous and intact?
Sealant: Is it flexible, bonded and free from splitting?
Joint edges: Are there cracks, spalling or impact damage?
Waterproofing: Is the waterproofing system continuous?
Drainage: Is water being directed away from the joint?
Structural condition: Is there evidence of excessive movement?
Traffic condition: Has vehicle loading damaged the joint?
Adjacent concrete: Is there cracking, delamination or corrosion?
Previous repairs: Have earlier repairs remained effective?
Where significant movement, cracking or water ingress is identified, further investigation may be required.
12. Repair and Refurbishment
Movement-joint repairs should be undertaken using a system appropriate for the anticipated movement and exposure conditions.
Repairs may include:
- Removal and replacement of failed sealant
- Replacement of backing material
- Repair of damaged concrete edges
- Replacement of joint nosings
- Renewal of waterproofing interfaces
- Installation of proprietary movement-joint systems
- Localised concrete repairs
- Drainage improvements
Before undertaking repairs, the cause of the defect should be established.
Simply filling a moving joint with rigid repair mortar is generally inappropriate because the material can restrict movement and subsequently crack.
Similarly, applying a rigid waterproof coating continuously across an active movement joint may result in premature failure.
For significant structural movement or persistent cracking, a structural engineer or suitably qualified specialist should assess the condition before repair works are specified.
13. Movement Joints and Refurbishment of Car Parks
During a multi-storey car park refurbishment, all existing movement joints should be identified before waterproofing, concrete repair or surface coating works commence.
The refurbishment assessment should establish:
- The location of existing joints.
- The type of joint system installed.
- The condition of the joint.
- The extent of movement.
- Whether the joint remains structurally appropriate.
- Whether the waterproofing remains continuous.
- Whether adjacent concrete has deteriorated.
- Whether vehicle loading has damaged the joint.
- Whether the existing joint can be retained.
- Whether replacement is required.
This is particularly important where a new car park waterproofing system is proposed.
The new waterproofing system must be detailed around the movement joints rather than simply applied continuously over them.
14. Benefits to Commercial Building Owners
Properly designed and maintained movement joints provide significant benefits to building owners and facility managers.
Reduced Water Ingress
Maintaining movement-joint integrity reduces the risk of water entering roofs, façades, podiums and car park decks.
Reduced Structural Deterioration
Preventing water and contaminants from reaching reinforced concrete helps protect the structure.
Lower Maintenance Costs
Early identification of failed joints allows relatively localised repairs before defects become widespread.
Improved Building Appearance
Movement joints help control cracking and prevent unsightly uncontrolled defects.
Improved Occupier and User Safety
Well-maintained joints reduce trip hazards and prevent deterioration in pedestrian and vehicle areas.
Extended Service Life
Effective movement control and waterproofing help preserve the building envelope and structural components.
Reduced Disruption
Planned maintenance can often be carried out before defects develop into major leaks or structural repairs, reducing disruption to commercial operations and car park users.
15. Why Movement-Joint Maintenance Is Necessary
Movement joints should not be regarded as a one-time construction item requiring no further attention.
They are active components of the building envelope and structural system.
Sealants can deteriorate due to ultraviolet exposure, temperature changes, ageing and repeated movement. Joint edges can become damaged by impact and traffic. Waterproofing interfaces can deteriorate, while debris can prevent the joint from functioning correctly.
Regular inspection therefore allows defects to be identified before they develop into more significant problems.
For a multi-storey car park, this maintenance is particularly important because deterioration of the waterproofing can contribute to reinforcement corrosion and concrete damage.
The Concrete Centre identifies durability as an important consideration for car park structures and highlights the importance of appropriate concrete specification and detailing.
16. Conclusion
Movement joints are an essential component of commercial buildings and multi-storey car parks because they allow buildings and structural elements to accommodate movement in a controlled manner.
They are necessary because concrete, masonry, steel and other construction materials naturally move in response to temperature, moisture, shrinkage, creep, loading and other environmental and structural conditions.
In commercial buildings, movement joints help control cracking within façades, walls, floors, roofs and other building elements.
In multi-storey car parks, their importance is even greater because the structure is exposed to weather, repeated vehicle loading, water, contaminants and potentially de-icing salts. Correctly designed movement joints help protect concrete decks, waterproofing systems and reinforcement from deterioration.
Movement joints therefore provide three fundamental functions:
They accommodate movement, control cracking and protect the building from water ingress.
Their effectiveness depends on correct design, appropriate materials, proper installation and ongoing maintenance. During refurbishment, existing joints should always be identified, inspected and incorporated into the new waterproofing and repair strategy.
For commercial buildings and multi-storey car parks, maintaining movement joints is therefore an important part of planned preventative maintenance, structural durability and long-term asset management. A relatively small defect within a movement joint can ultimately contribute to much larger waterproofing and structural problems if it is not identified and repaired at an early stage.