Concrete movement joints are a critical component of structural design in residential, commercial and post-tensioned (PT) slab construction. Yet one of the most common questions during design and value engineering is:
Should a temporary movement joint be used, or is a permanent Slipjoint system required?
Understanding the difference between early-age concrete movement and long-term structural movement is essential when selecting the appropriate expansion joint system.
Why Concrete Movement Joints Are Necessary
All concrete structures experience movement. This includes:
- Drying shrinkage
- Creep under sustained loads
- Thermal expansion and contraction
- Post-tension slab shortening
- Differential shortening between slabs, walls and cores
In multi-storey residential buildings, long slab runs and vertical structural elements amplify these effects. Without properly designed movement joints in concrete slabs, restraint stresses can lead to cracking, joint edge spalling and long-term serviceability issues. The key question is not whether movement will occur, but how long that movement must be accommodated.
Temporary Movement Joints: Managing Early-Age Shrinkage
During the first 28 to 90 days after construction, concrete undergoes significant early-age shrinkage. In most structural design details, interfaces are intentionally allowed to move during this period before being locked via grout or tie connections.
In these cases, a temporary movement joint such as Galvanised M.S Grease Slipjoints (HGSJ) may be appropriate. Grease Slipjoints provides a low-friction interface between steel layers, allowing early-age concrete movement with minimal restraint. Their performance is governed by contact stress and friction characteristics rather than long-term structural capacity.
However, grease-based systems are not designed as permanent expansion joints in concrete slabs. Over time, the grease layer will dry and the interface may cease to function as an active sliding surface.
Temporary movement joints are therefore suited to:
• Early-age PT slab movement
• Construction-phase debonding
• Interfaces that will be structurally locked after curing
• Interfaces where zero rotational movement is expected
• They are not intended for ongoing structural movement over the life of the building.
Permanent Movement Joints: Accommodating Design-Life Movement
Concrete does not stop moving after the curing phase. Residential and commercial buildings continue to experience shrinkage, creep and thermal cycling for decades. In long slab runs or multi-storey residential developments, cumulative movement can be significant.
Where movement is expected to occur over the full design life of the structure, a permanent movement joint system such as Hercuslip Composite (HSC) is required. Composite Slipjoints are engineered specifically for sustained sliding performance. Unlike temporary grease systems, they provide:
• Permanent low-friction sliding capability
• Defined compressive performance
• Long-term reliability under sustained loads
• Suitability for large-scale concrete movement joints
Concrete Expansion Joint Selection: What Determines the Right System?
When selecting between a temporary and permanent movement joints, the determining factor is the expected duration of movement. If the structural interface will be locked after early-age shrinkage and no further sliding is required, a temporary grease slipjoint may be sufficient.
If the building will continue to experience movement due to creep, thermal effects or differential shortening, particularly in multi-storey buildings with extensive movement joint runs, a permanent composite expansion joint is necessary.
Substituting a temporary movement joint in a permanent application can result in:
• Restrained concrete shrinkage cracking
• Joint edge damage
• Loss of sliding capability
• Increased defect liability
• Costly remedial works
Conclusion: Temporary vs Permanent Movement Joints
The difference between temporary and permanent movement joints is not simply cost — it is structural intent.
Temporary Grease Slipjoints are suitable for early-age concrete movement where interfaces will be locked or where no ongoing sliding is required. Permanent Composite Slipjoints are required where movement and rotation is part of the building’s long-term behaviour. When designing or reviewing concrete expansion joints in residential or commercial projects, understanding the expected movement profile is essential to selecting the appropriate system.
For more information regarding movement joint suitability for your project, please contact a member our team for further assistance.