Temporary works failures on UK construction projects are rarely caused by a single design error. In London, where projects involve complex sequencing, constrained environments and multiple interfaces, failures are often linked to inadequate checking and verification of temporary works designs before they are implemented.
Under BS 5975, all temporary works designs must be checked to ensure they are suitable, safe and compliant. The level of checking required is defined through a system of design check categories, ranging from simple standard solutions to complex independent third-party checks.
What Are Temporary Works Design Checks?
Temporary works design checks are a formal verification process to confirm that a design is correct, suitable for its intended purpose and compliant with the design brief.
This process ensures that errors, omissions or incorrect assumptions are identified before construction, reducing the risk of failure during implementation.
BS 5975 requires that all temporary works designs are checked by a competent person, with the level of independence increasing depending on the complexity and risk of the design.
Understanding Design Check Categories (0–3)
BS 5975 defines four design check categories, which determine how a temporary works design must be reviewed.
Category 0 – Standard Solutions
This applies to standard or proprietary solutions where the design has already been established. A simple check is required to confirm that the solution is suitable for the specific conditions.
Category 1 – Simple Designs
These are straightforward temporary works designs using standard methods and calculations. The check can be carried out by another competent person within the same organisation.
Category 2 – Complex Designs
These involve more complex structures or loading conditions. A more rigorous check is required, typically by someone independent from the original designer.
Category 3 – High-Risk or Innovative Designs
These are complex or unusual designs where failure would have significant consequences. An independent third-party check is required, often involving full recalculation of the design.
The higher the category, the greater the level of independence required in the checking process.
How Design Checks Fit Into the Temporary Works Process
Design checks are part of the wider temporary works control system, linking design, coordination and site implementation.
As outlined in Temporary Works Register Explained (BS 5975): What It Is and What It Must Include, the register provides a central record of all temporary works on a project and tracks their design, approval and implementation status. This ensures that no temporary works are installed or used without a verified and approved design.
The design check category must be identified early in the process and recorded in the Temporary Works Register, allowing the Temporary Works Coordinator (TWC) to ensure that the correct level of checking is carried out before implementation.
Who Is Responsible for Design Checks?
The Temporary Works Designer (TWD) is responsible for producing the design and advising on the appropriate design check category.
The Temporary Works Coordinator (TWC) is responsible for ensuring that the design is checked in accordance with BS 5975 and that the correct procedures are followed before implementation.
The Temporary Works Design Checker (TWDC) carries out the check, with their level of independence determined by the design check category.
This separation of responsibilities ensures that designs are independently verified before being used on site.
Why Design Checks Are Critical
Temporary works designs often involve temporary load paths, changing conditions and partial structural stability.
This can include supporting excavations, formwork during concrete pours, or propping systems that carry significant loads before the permanent works are complete.
Without proper checking, design errors can go unnoticed, leading to structural instability, collapse or safety incidents.
Design checks provide a formal verification process that reduces these risks by ensuring that designs are reviewed by competent and, where required, independent engineers.
Common Failures in Design Checking
Failures in temporary works are often linked to weaknesses in the design check process. Common issues include:
In some cases, designs are implemented without any formal check, particularly under programme pressure, increasing the risk of failure.
Another common issue is misunderstanding the complexity of the temporary works, leading to an inappropriate check category being applied.
What This Means on Site
In practical terms, design checks must be treated as a critical control point, not a formality.
On site, this means:
Where this process is properly followed, it provides a structured system that reduces risk and supports safe construction.
Where it is not followed, temporary works may be installed without adequate verification, increasing the likelihood of failure.
Evidence-Based Summary
Temporary works safety is not driven by design alone but by a combination of design, verification and procedural control. While designs may be technically correct, evidence shows that failures often occur where design checks are inadequate, incorrectly categorised or not independently verified.
In practical terms, this means that the BS 5975 design check process is a critical safeguard, ensuring that temporary works designs are properly reviewed before being implemented on site.
Under BS 5975, all temporary works designs must be checked to ensure they are suitable, safe and compliant. The level of checking required is defined through a system of design check categories, ranging from simple standard solutions to complex independent third-party checks.
What Are Temporary Works Design Checks?
Temporary works design checks are a formal verification process to confirm that a design is correct, suitable for its intended purpose and compliant with the design brief.
This process ensures that errors, omissions or incorrect assumptions are identified before construction, reducing the risk of failure during implementation.
BS 5975 requires that all temporary works designs are checked by a competent person, with the level of independence increasing depending on the complexity and risk of the design.
Understanding Design Check Categories (0–3)
BS 5975 defines four design check categories, which determine how a temporary works design must be reviewed.
Category 0 – Standard Solutions
This applies to standard or proprietary solutions where the design has already been established. A simple check is required to confirm that the solution is suitable for the specific conditions.
Category 1 – Simple Designs
These are straightforward temporary works designs using standard methods and calculations. The check can be carried out by another competent person within the same organisation.
Category 2 – Complex Designs
These involve more complex structures or loading conditions. A more rigorous check is required, typically by someone independent from the original designer.
Category 3 – High-Risk or Innovative Designs
These are complex or unusual designs where failure would have significant consequences. An independent third-party check is required, often involving full recalculation of the design.
The higher the category, the greater the level of independence required in the checking process.
How Design Checks Fit Into the Temporary Works Process
Design checks are part of the wider temporary works control system, linking design, coordination and site implementation.
As outlined in Temporary Works Register Explained (BS 5975): What It Is and What It Must Include, the register provides a central record of all temporary works on a project and tracks their design, approval and implementation status. This ensures that no temporary works are installed or used without a verified and approved design.
The design check category must be identified early in the process and recorded in the Temporary Works Register, allowing the Temporary Works Coordinator (TWC) to ensure that the correct level of checking is carried out before implementation.
Who Is Responsible for Design Checks?
The Temporary Works Designer (TWD) is responsible for producing the design and advising on the appropriate design check category.
The Temporary Works Coordinator (TWC) is responsible for ensuring that the design is checked in accordance with BS 5975 and that the correct procedures are followed before implementation.
The Temporary Works Design Checker (TWDC) carries out the check, with their level of independence determined by the design check category.
This separation of responsibilities ensures that designs are independently verified before being used on site.
Why Design Checks Are Critical
Temporary works designs often involve temporary load paths, changing conditions and partial structural stability.
This can include supporting excavations, formwork during concrete pours, or propping systems that carry significant loads before the permanent works are complete.
Without proper checking, design errors can go unnoticed, leading to structural instability, collapse or safety incidents.
Design checks provide a formal verification process that reduces these risks by ensuring that designs are reviewed by competent and, where required, independent engineers.
Common Failures in Design Checking
Failures in temporary works are often linked to weaknesses in the design check process. Common issues include:
- Incorrect assignment of design check category
- Checks carried out by insufficiently independent personnel
- Incomplete or rushed design reviews
- Changes to design not being re-checked
- Lack of documentation or certification
In some cases, designs are implemented without any formal check, particularly under programme pressure, increasing the risk of failure.
Another common issue is misunderstanding the complexity of the temporary works, leading to an inappropriate check category being applied.
What This Means on Site
In practical terms, design checks must be treated as a critical control point, not a formality.
On site, this means:
- Identifying the correct design check category at an early stage
- Ensuring checks are carried out by competent and independent personnel
- Recording design checks in the Temporary Works Register
- Preventing implementation until checks are complete and approved
Where this process is properly followed, it provides a structured system that reduces risk and supports safe construction.
Where it is not followed, temporary works may be installed without adequate verification, increasing the likelihood of failure.
Evidence-Based Summary
Temporary works safety is not driven by design alone but by a combination of design, verification and procedural control. While designs may be technically correct, evidence shows that failures often occur where design checks are inadequate, incorrectly categorised or not independently verified.
In practical terms, this means that the BS 5975 design check process is a critical safeguard, ensuring that temporary works designs are properly reviewed before being implemented on site.
Image © London Construction Magazine Limited
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
