Understanding the Difference Between Temporary Works and Permanent Works

In construction, safety and stability begin long before the first brick is laid. One of the most important distinctions for engineers, contractors, and site managers to understand is the difference between Temporary Works and Permanent Works. Both are essential parts of any successful project; each with unique design principles, safety requirements, and legal responsibilities.

Key Differences at a Glance

• Permanent Works form the completed structure — designed to remain in place for the lifespan of the asset.
• Temporary Works provide essential support or access during construction and are removed, modified, or incorporated into the final build.
• Each type requires distinct planning, design, and safety checks under UK legislation.
• BS 5975 sets the recognised framework for managing Temporary Works in the UK.

What Are Permanent Works?

Permanent Works are typically designed by architects and structural engineers and are subject to rigorous checks to ensure they can safely support loads throughout the asset’s lifecycle.

Examples include:

• Foundations and substructures
• Structural walls, beams, and slabs
• Roofs, facades, and columns
• Drainage, utility systems, and retaining walls

Permanent Works are typically designed by architects and structural engineers and are subject to rigorous checks to ensure they can safely support loads throughout the asset’s lifecycle.

What Are Temporary Works?

Temporary Works are the temporary structures, supports, or systems that make construction possible, providing stability, access, and protection during the build. While they may not form part of the final structure, their correct design and control are critical for site safety and project success.

Examples include:

• Scaffolding and access towers
• Formwork and falsework for concrete pours
• Shoring and excavation support systems
• Temporary bridges, platforms, and hoardings
• Edge protection and temporary barriers

Temporary Works must be planned, designed, checked, and managed according to BS 5975, which requires formal procedures and the appointment of competent personnel; such as a Temporary Works Co-ordinator (TWC) and Supervisor (TWS) — to oversee safety and compliance.

Legal Duties in the UK

Both Temporary and Permanent Works must comply with key legislation, including:

• Health and Safety at Work etc. Act 1974
• Construction (Design and Management) Regulations 2015 (CDM 2015)
• Building Regulations 2010

Duty holders — including clients, designers, principal contractors, and contractors are legally required to ensure works are properly planned, coordinated, and executed safely.

Real-World Examples

High-Rise Construction

• Temporary Works: Formwork and scaffolding to shape and access upper floors.
• Permanent Works: Reinforced concrete slabs, core walls, and facade systems.

Bridge Projects

• Temporary Works: Falsework, props, and access scaffolds.
• Permanent Works: Decks, abutments, piers, and expansion joints.

Tunnel Construction

• Temporary Works: Excavation support, lining moulds, and ventilation systems.
• Permanent Works: Concrete tunnel linings and waterproofing membranes.

When Temporary Works Become Permanent

In some cases, Temporary Works can be integrated into the final structure if designed appropriately. Examples include:

• Foundation or diaphragm walls reused as permanent retaining structures.
• Metal decking used as permanent formwork for slabs or bridge decks.
• Tower or mobile crane foundations repurposed as sub-bases for car parks.
• Lifting anchors and embedded fittings left as part of the permanent structure.

Where this occurs, elements must meet all design and durability standards applicable to permanent structures, requiring close collaboration between Temporary and Permanent Works designers.

Why This Distinction Matters

Understanding the difference between Temporary and Permanent Works isn’t just technical, it’s essential for project safety, efficiency, and legal compliance. Miscommunication or design overlap can lead to delays, safety incidents, and costly rework.

By ensuring clear coordination, competent supervision, and compliance with BS 5975 and CDM 2015, construction teams can deliver safer, more efficient projects — every time.

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