The management of temporary works in the construction industry
SIM 02/2010/04
SIM 02/2010/04 is currently being revised but this work is on hold pending publication of the next revision of BS5975. The content of the SIM remains valid. However readers should note that the listed legislation has been updated and reference should be made to the Construction (Design and Management) Regulations 2015 which has replaced the 2007 version referred to. Changes affecting this SIM are largely limited to changes to the applicable Regulation number - with the exception that, in this SIM only, the term 'Principal Designer' can be directly substituted for the listed term 'CDM Coordinator'. This can be done without affecting the accuracy of the text. Where the SIM refers to an Approved Code of Practice (ACOP) reference should instead be made to HSE Guidance publication L153 which is freely available via the HSE website.
- Summary
- Purpose
- Background
- Temporary Works Management
- Action by Inspectors
- Advice and Support
- References
- Appendix 1 – temporary works design principles and the consequences and causes of failure
- Appendix 2 – the impact of changes to the construction industry on temporary works management and the history of BS 5975
Summary
This SIM provides guidance to Inspectors on temporary works management in the construction industry and how Inspectors should approach enforcement of the topic.
Purpose
This document should be used as the basis for undertaking operational work on this topic in accordance with Construction Division's current work plan. This is a new topic introduced in to the work plan in order to highlight and better control the risks associated with all types of temporary works on construction sites (although there are clear links to existing priorities, eg tower crane safety and structural stability). As this is new work, the SIM will be reviewed and revised in the light of operational experience and, as such, constructive feedback would be welcomed.
The aim of the planned work is to:
Promote awareness and knowledge of the importance of managing temporary works Improve contractors' management arrangements of temporary works Increase the competence of those engaged in temporary works management and design Reduce accidents arising from temporary works failures
Background
"Temporary works" is a widely used expression in the construction industry for an "engineered solution" used to support or protect an existing structure or the permanent works during construction, or to support an item of plant or equipment, or the vertical sides or side-slopes of an excavation, or to provide access. The construction of most types of permanent works will require the use of some form of temporary works.
Temporary works is defined in BS5975: 2008 "Code of practice for temporary works procedures and the permissible stress design of falsework" as "(those) parts of the works that allow or enable construction of, protect, support or provide access to, the permanent works and which might or might not remain in place at the completion of the works".
Examples of temporary works include, but are not limited to:
Earthworks - trenches, excavations, temporary slopes and stockpiles. Structures - formwork, falsework, propping, façade retention, needling, shoring, edge protection, scaffolding, temporary bridges, site hoarding and signage, site fencing, cofferdams.
Equipment/plant foundations - tower crane bases, supports, anchors and ties for construction hoists and mast climbing work platforms (MCWPs), groundworks to provide suitable locations for plant erection, eg mobile cranes and piling rigs. Further information on temporary works design principles and the consequences and causes of failure are set out in Appendix 1.
Temporary Works Management
The correct design and execution of temporary works is an essential element of risk prevention and mitigation in construction. BS 5975 provides recommendations and guidance on the procedural controls to be applied to all aspects of temporary works in the construction industry and on the design, specification, construction, use and dismantling of falsework. Background information on the impact of changes to the construction industry on temporary works management and the history of BS 5975 are set out in Appendix 2.
Temporary works procedures
Contractors should be able to demonstrate that they have in place effective arrangements for controlling risks arising from the use of temporary works. These are usually captured in a temporary works procedure which will contain most or all of the following elements:
- Appointment of a Temporary Works Co-ordinator (TWC)
- Preparation of an adequate design brief.
- Completion and maintenance of a temporary works register
- Production of a temporary works design (including a design risk assessment and a designer's method statement where appropriate).
- Independent checking of the temporary works design.
- Issue of a design/design check certificate, if appropriate.
- Pre-erection inspection of the temporary works materials and components.
Control and supervision of the erection, safe use, maintenance and dismantling of the temporary works – ie, procedures to:
- Check that the temporary works have been erected in accordance with the design, and issue a formal "permit to load" where necessary.
- Confirm when the permanent works have attained adequate strength to allow dismantling of the temporary works, and issue a formal "permit to dismantle" where necessary.
- The procedure should include measures to ensure that the design function, the role of TWC, and Temporary Works Supervisor(s) where appropriate, are carried out by competent individuals.
- Smaller contractors may not have the experience to operate their own temporary works procedure and may need to obtain external expertise. It is also common for large and medium contractors to outsource aspects of temporary works design and management.
Temporary Works Coordinator (TWC)
The TWC is responsible for ensuring that the contractor's procedures for the control of temporary works are implemented on site. The TWC is not normally the designer, but is responsible for ensuring that a suitable temporary works design is prepared, checked and implemented on site in accordance with the relevant drawings and specification.
The principal activities of the TWC are listed in Clause 7.2.5 of BS5975:2008. On some projects, particularly smaller jobs involving lower risk temporary works, it may be appropriate for the TWC and designer roles to be carried out by the same person, provided that he/she is competent to carry out each of the roles.
The TWC for a project should be formally appointed and have adequate authority to carry out his/her tasks, including stopping the work if it is not satisfactory. It is essential that those selected to act as TWC are competent with relevant up-to-date training, and experience and qualifications appropriate to the complexity of the project. Ideally a TWC would:
- Have experience of the relevant types of temporary works.
- Have completed formal TWC training.
- Hold a Degree / HND in civil/ structural engineering.
- Be a Chartered Civil / Structural Engineer
Although a Chartered Civil or Structural Engineering qualification is desirable, the numbers with these qualifications and with experience of the co-ordination of temporary works, is unlikely to be sufficient to provide cover for all projects. The key attributes of a competent TWC are in order of priority,
- relevant experience,
- formal TWC training and
- professional qualifications.
- TWCs should have the competence and authority to be effective.
Temporary Works Supervisor (TWS)
On larger sites, or where a number of subcontractors are involved, it may be appropriate for one or more Temporary Works Supervisors (TWS) to be appointed. A TWS should be responsible to the TWC and assist the TWC in the supervision of temporary works.
Temporary Works Register
It is useful for a temporary works register to be prepared for any project,.It should contain a list of all identified temporary works items associated with the project. These can be set out as a table using appropriate headings, which could include:
- Design brief number (for each item) and date issued
- Short description of temporary works
- Date required
- Category of temporary works
- Designer
- Design Checker
- Date design complete
- Date design checked/approved
- Erection complete and checked or "Permit to Load" "Permit to Dismantle"
Design brief
A design brief should be prepared for each item of temporary works to serve as the focus for subsequent decisions, design work calculations and drawings. It should include all data relevant to the design of the temporary works and should be prepared in good time to allow for all subsequent activities. The brief may be relatively simple for the smaller schemes, but for major work, more information will need to be collected and collated before design work can commence. The TWC should ensure that an adequate design brief is provided to the designer and design checker of the temporary works.
Temporary works design
The design of the temporary works should be based on the agreed design brief. Any proposed alteration or modification of the design brief by the designer should be referred back to the TWC. The temporary works should be designed in accordance with recognised engineering principles. The preparation of design calculations, drawings and specification should be undertaken with similar rigour to the procedures applied to the design of the permanent works.
Temporary works designers include; the manufacturers and suppliers of proprietary temporary works equipment and those working in a contractor's temporary works department or office. Temporary works designs are sometimes categorised to indicate the complexity/simplicity of the specific temporary works structure and the potential risk. See below for an example
Simple and/or potentially low risk temporary works
- Standard scaffold
- Formwork less than 1.2m high
- Hoarding and fencing up to 1.2m high
- Simple propping schemes – 1 or 2 props
- Internal hoarding systems and temporary partitions not subject to wind loading
- Shallow excavations less than 1.2m deep/high
More complex and/or potentially medium risk temporary works
- Falsework up to 3m high
- Formwork for columns and walls up to 3m high
- More complex propping schemes – multiple props at single level
- Needling of structures up to 2 storeys high
- Excavations up to 3m deep/high
- net systems not fixed to robust primary members
- Hoarding and fencing up to 3m high
- Simple designed scaffold
- Temporary roofs
Complex and/or potentially high risk temporary works
- Falsework and formwork over 3m high
- Trenchless construction, including headings, thrust bores, mini tunnels
- Working platforms for cranes and piling rigs
- Tower crane bases
- Façade retention schemes
- Flying and raking shores
- Complex propping schemes – multiple props and multiple levels
- Needling of structures greater than 2 storeys high
- Ground support schemes greater than 3m deep
- Complex designed scaffold
- Cofferdams
- Bridge erection schemes
- Jacking schemes
- Complex structural steelwork and precast concrete erection schemes
- Hoarding and fencing over 3m high
In practice, even relatively simple temporary works may require careful consideration in their design, construction, commissioning, inspection and loading. An apparently simple temporary works job could lead to failure and even to fatalities if it is not competently executed. The choice of the appropriate temporary works solution, including the use of "standard solutions," is discussed in Clause 9.4 of BS5975: 2008. A "standard solution" is an arrangement for which the basic design work has already been carried out and is presented in a tabular or similar form, and for which no further calculations are required.
Design Checks
Before erection commences, the temporary works design should be checked for:
- Design concept
- Strength and structural adequacy (including foundations and lateral stability)
- Compliance with the design brief.
The design check should be carried out by an independent competent person(s) . The ability and independence of the checker should be greater where the temporary works are more complex or where new ideas are incorporated. Recommendations for various categories of design check are given in Table 1 of BS5975:2008, reproduced below:
| Category | Scope | Comment | Independence of checker |
|---|---|---|---|
| 0 | Restricted to standard solutions only, to ensure the site conditions do not conflict with the scope or limitations of the chosen standard solution. | This applies to the use of standard solutions and not the original design which will require both structural calculation and checking to category 1, 2 or 3 as appropriate. | Because this is a site issue, the check may be carried out by another member of site or design team. |
| 1 | For simple designs. These may include: formwork: false work (where top restraint is not assumed): needling and propping to brickwork openings in single storey construction. | Such designs would be undertaken using simple methods of analysis and be in accordance with the relevant standards, supplier's technical literature or other reference publications. | The check may be carried out by another member of the design team. |
| 2 | On more complex or involved designs. Designs for excavations, for foundations, for structural steelwork connections, for reinforced concrete. | Category 2 checks would include designs where a considerable degree of interpretation of loading or soils' information is required before the design of the foundations or excavation support or slope | The check should be carried out by an individual not involved in the design and not consulted by the designer. |
| 3 | For complex or innovative designs, which result in complex sequences of moving and/or construction of either the temporary works or permanent works. | These designs include unusual designs or where significant departures from standards, novel methods of analysis or considerable exercise of engineering judgement are involved. | The check should be carried out by another organization |
Temporary works management arrangements suitable for small contractors
For smaller contractors, the principles of BS5975 should be in place if not the formal and specific procedures, in particular:
- ensuring a suitably competent temporary works designer/adviser is in place to supply an engineered solution,
- adequate information flow,
- design checking to an appropriate level,
- suitable verification of correct erection of the temporary works and someone overseeing and co-ordinating the whole process.
Smaller contractors may not have anyone sufficiently experienced to plan effectively all but the most simple temporary works. There should be clear evidence that appropriate external expertise has been engaged. This includes obtaining the services of a suitably competent TWC and temporary works designer to ensure temporary works are effectively designed, constructed, inspected, loaded and managed. On some projects, particularly smaller jobs involving low risk temporary works, it may be appropriate for the TWC and designer roles to be carried out by the same person.
The role of CDM co-ordinators
CDM co-ordinators should take reasonable steps to ensure co-operation between permanent and temporary works designers, in particular to ensure that arrangements are in place to ensure that designs are compatible and that the permanent works can support any loadings from temporary works. CDM co-ordinators also have a duty to advise clients on the suitability of the initial construction phase plan. Amongst the topics that need to be considered when drawing up the construction phase plan, as listed in the ACOP, are the arrangements for controlling significant site risks including, the "stability of structures whilst carrying out construction work, including temporary structures and existing unstable structures" and "work on excavations and work where there are poor ground conditions".
Action by Inspectors
General
Inspectors should focus their attention mainly on ensuring that appropriate temporary works management arrangements and procedures have been adopted commensurate with the scale and complexity of the project and the construction risks involved.
The expectation is that medium to large projects, and those with complex and/or high risk temporary works, will have formal management procedures in place specifically following the recommendations in BS5975. For smaller contractors and smaller simpler, projects, we would be looking for the principles of BS5975 to be in place.
Judgment will be required regarding the extent to which procedures should be formalized, depending on the degree of risk rather than size of project. We want to see good management of temporary works. BS5975 is an established standard representing good practice, but it also provides a useful yardstick for checking that essential elements of a management system are in place.
Legislation
The Construction (Design and Management) Regulations 2007 (CDM 2007) and associated Approved Code of Practice (ACOP) are directly applicable to the design and management of temporary works. The definition of a structure in the regulations includes "any formwork, falsework, scaffold or other structure designed or used to provide support or means of access during construction work." In the ACOP, designers include "temporary works engineers, including those designing auxiliary structures, such as formwork, falsework, façade retention schemes, scaffolding, and sheet piling." Temporary works designers have exactly the same designer duties as permanent works designers on CDM-notifiable projects.
CDM 2007 make several direct or implied references to the design and construction, inspection and management of temporary works and the competence of those involved in their provision:
PART 2 General management duties applying to construction projects
- Regulation 4 (competence): competence required of all those with a role to discharge in the planning, design and execution of temporary works.
- Regulations 5 and 6 (cooperation and coordination): cooperation and coordination of activities, including temporary works, incumbent on all involved.
- Regulation 10 (client's duty to provide information): provision by client of pre-construction information (eg ground conditions, structural drawings).
- Regulation 11 (duties of designers): avoidance of foreseeable risk arising from preparing or modifying designs.
- Regulation 13 (duties of contractors): planning, management and monitoring of construction work.
PART 3 Additional duties where project is notifiable
- Regulation 18 (additional duties of designers): provision of information to assist the CDM co-ordinator.
- Regulation 20 (duties of CDM co-ordinators): all reasonable steps to ensure designers comply with their duties and to ensure cooperation between designers and principal contractors in relation to any design or design change.
- Regulation 22 (duties of the principal contractor): planning, managing and monitoring the construction phase.
PART 4 Duties relating to health and safety on construction sites
- Regulation 28 (stability of structures): any support or temporary structure must be designed, installed and maintained so as to withstand foreseeable loads.
- Regulation 29 (demolition or dismantling): planning and recording of arrangements.
- Regulation 31 (excavations): planning and execution.
- Regulation 32 (cofferdams and caissons): design, planning and execution.
Enforcement guidance
Failure to properly plan and execute temporary works constitutes a "risk of serious personal injury" and could result in a fatal, or a major injury as defined by RIDDOR 1995 Reg. 2 could occur. The likelihood of this occurring is set out in the risk matrix below:
| Consequence | Application / Interpretation |
Likelihood | |||
|---|---|---|---|---|---|
| Probable | Possible | Remote | Nil/ negligible | ||
| Risk of serious personal injury | Collapse of permanent structure due to inadequate temporary works |
High risk or complex temporary works being used without the key elements of a temporary works procedure in place, particularly absence of evidence of the temporary works being designed by a competent person |
High risk or complex temporary works being used with most of the key elements of a temporary works procedure in place but absence of evidence of temporary works designs being independently verified. |
Medium risk temporary works being used with most of the key elements of a temporary works procedure in place but absence of some elements requiring improvement. |
A temporary works procedure for all categories consistent with the advice in this SIM is in place and evidence it is being used effectively |
Enforcement action
The first consideration is whether there is a need to prohibit some or all aspects of the temporary works (whether planned or in progress) before considering further action. If there is clear evidence of risk, eg signs of structural distress (distortion, missing bracing, poor foundations, damaged components), overloading of temporary works, risk of falls from height, a prohibition notice is clearly appropriate. Even where there is no patent evidence of risk but there is no effective temporary works procedure being employed a prohibition notice might still be required dependent on the type and complexity of temporary works in use or planned and the competence of those undertaking the work.
The absence or inadequacy of temporary works procedures should be addressed as an underlying management failing. Regulation 13 (2) CDM 2007 can be used to require that temporary works are planned, managed and monitored in a way which ensures, so far as is reasonably practicable, they are carried out without risks to health and safety.
For CDM-notifiable projects where there is evidence of a lack of effective input by the CDM co-ordinator (eg co-operation between temporary and permanent works designers, adequate construction phase plan arrangements for dealing with risks), a letter to the CDM co-ordinator would be appropriate.
The following matrix provides guidance on initial enforcement expectations depending on the likelihood of risk. (The multiple casualties table in EMM has been applied).
| Control failure | Risk of serious personal injury likelihood | Initial enforcement expectation | ||
|---|---|---|---|---|
| Consider PN | Consider IN | Consider letter | ||
| No temporary works procedure and high risk or complex temporary works in use or planned | Probable | x | x | |
| Inadequate temporary works procedures and medium risk temporary works in use or planned | Possible | x | ||
| Absence of effective input from CDM co-ordinator demonstrated by lack of co-operation between temporary and permanent works designers and/or, inadequate temporary works arrangements in construction phase plan | Possible/Remote | x | ||
Advice and Support
| Role | Office |
|---|---|
| Construction Engineering Specialist Team (CEST) Topic Lead | Cardiff |
| Sector Lead | Leeds |
| Management of CEST (South) Support | East Grinstead |
| Management of CEST (North) Support | Bootle |
References
BSI, BS 5975+A1:2011 Code of practice for temporary works procedures and the permissible stress design of falsework, London, BSI, 2011
THE CONCRETE SOCIETY, Falsework – Report of the joint committee, The Concrete Society and the Institution of Structural Engineers, Technical Report TRCS 4, London, July 1971.
BRAGG, S.L.(DEPARTMENT OF EMPLOYMENT, DEPARTMENT OF THE ENVIRONMENT), Interim Report of the Advisory Committee on Falsework, London, HMSO, 1974.
BRAGG, S.L.(DEPARTMENT OF EMPLOYMENT, DEPARTMENT OF THE ENVIRONMENT), Final Report of the Advisory Committee on Falsework, London, HMSO, June 1975.
PALLETT, P.F. et al (HSE), Investigation into aspects of falsework, HSE Contract Research Report 394/2001, HMSO, 2001.
STANDING COMMITTEE ON STRUCTURAL SAFETY (SCOSS), Falsework: full circle?, SCOSS Topic Paper SC/T/02/01, 2002
Appendix 1 – temporary works design principles and the consequences and causes of failure
Design principles
In order to ensure the strength and stability of any temporary works structure, there are 3 fundamental aspects that need to be considered which can be simplified as follows:
- Foundations – the ability of the ground to carry the loads transmitted from the temporary works structure without failure or excessive deformation or settlement.
- Structural integrity – the ability of the temporary works structure itself to carry and transmit loads to the ground via the foundations without failure of the structural elements, including fixings and connections (eg by buckling, bending, shear, tension, torsion), and without excessive deflection.
- Stability – the ability of the temporary works structure to withstand horizontal or lateral loading without sway, overturning or sliding failure (stability may be inherent in the temporary works structure itself or provided by the permanent works).
Consequences of temporary works failure
Failure to adequately design, construct and maintain temporary works can lead to:
- Collapse or failure of the temporary works
- Structural failures and collapse of the permanent works
- Uncontrolled ingress or egress of materials, spoil and water
- Collapse of adjacent structures (buildings, transport systems, infrastructure)
- Risk of single/multiple fatalities and serious injuries to workers and members of the public
- Risk of significant delay and increased costs to construction projects
- Significant financial and commercial risks to contractors, sub-contractors, designers, suppliers, and clients
Causes of temporary works failures
The main causes of temporary works failures include:
- Absence of or an inadequate temporary works procedure
- No temporary works coordinator (TWC) appointed
- Inadequate site investigation (including geotechnical investigation, identification of underground services, assessment of the structural condition of existing and/or adjacent buildings)
- Inadequate, or lack of, design brief
- Inadequate, or lack of, design for the temporary works
- Inadequate, or lack of, appropriate level of checking of temporary works designs
- Lack of awareness on site of temporary works design assumptions
- Unavailability of temporary works equipment
- Inappropriate use of temporary works equipment
- Poorly constructed temporary works and/or absence of checking of adequate erection.
- Unauthorised changes to an approved temporary works design
- Overloading of temporary works, ie failure to control loading or lack of awareness of the capacity of the equipment (eg acrow props)
- Inadequate communication of details of the temporary works design to the erectors
- Inadequate foundations for the temporary works
- Lack of adequate lateral stability for the temporary works
Appendix 2 – the impact of changes to the construction industry on temporary works management and the history of BS 5975
Industry changes
There have been significant changes to the construction industry since the mid 1970's which have affected how falsework, and more generally temporary works, are dealt with. Recent research5 identified the principal changes, including:
- Few "main contractors" now have their own temporary works departments whereas, in the 1970s, almost all would design temporary works in-house; the responsibility for temporary works now often falls to a specialist contractor/ supplier which can result in a lengthy supply chain.
- In the 1970s, most falsework and temporary works were constructed from scaffold "tube and fittings" whereas proprietary systems now dominate the market; therefore, the design skills and knowledge of the performance of the systems now tends to lie within the specialist organisations.
- There has been a gradual but inexorable loss of traditional skills within the construction industry; in practical terms, this means that the site foreman with a lifetime's experience of "what works" has been largely lost.
- Procurement routes are now largely chosen to maximise commercial benefit with little regard to considerations for the flow of information; the difficulties caused by long supply chains are further exacerbated when design and erection responsibility are split, and when design/supply briefs do not provide for site visits/inspections.
Research4 into various aspects of falsework produced some worrying findings which included:
- A lack of understanding at all levels of the fundamentals of stability of falsework and the basic principles involved.
- Wind loading is rarely considered.
- A lack of clarity in terms of the design brief and coverage of key aspects such as ground conditions.
- The assumptions for lateral restraint of the falsework made by designers were often ignored or misunderstood by those on site.
- A lack of adequate design checking and erection accuracy.
- Based on the research, a number of key concerns were identified:
- Competency of the falsework/temporary works designer.
- Sufficiency of information.
- Adequacy of supervision.
- Role of the Temporary Works Co-ordinator
- Competency of those erecting falsework/temporary works.
The actions to deal with these concerns are straightforward and require no more than the application of the good practice given in BS5975:2008. They also fit well with the aspirations of the CDM Regulations 2007 in respect of their aim of improving the overall co-ordination and management of health and safety throughout all stages of a construction project.
History of BS5975
The Code of Practice was first published in 1982 as BS5975:1982 Code of practice for falsework, following a number of significant falsework collapses in the 1970s and an apparent lack of authoritative guidance. A report on falsework1 by the Joint Committee of the Institution of Structural Engineers and the Concrete Society in 1971 was followed by an advisory committee to investigate the use of falsework, which produced reports2,3 in 1974/5, the Bragg Reports. Industry then produced the first code of practice (in compliance with one of the recommendations of the final Bragg Report) and it reflected the recommendations of the Bragg Report and was based on the Joint Committee report.
BS5975:1982 codified all relevant aspects that should be considered when preparing a design for falsework and included recommendations for materials, design and work on site. It described procedures as well as technical aspects because the success of falsework is closely linked to its management. Recommendations were given on the actions that should be taken and the allocation of duties to individuals. The Bragg Report recommended that the duty of ensuring that all the relevant procedures and checks are carried out be given to one individual known as the "Temporary Works Co-ordinator". BS5975:1982 included this recommendation but adopted the narrower term of "Falsework Co-ordinator" because the section on procedures only considered falsework and not the wider activities covered by the more general term of temporary works, such as scaffolding and excavations.
BS5975 was revised in 2008 and now provides recommendations and guidance on the procedural controls to be applied to all aspects of temporary works in the construction industry, as well as specific guidance on the design, specification, construction, use and dismantling of falsework. BS5975 describes procedures as well as technical aspects because the success of falsework and temporary works is closely linked to their management. Recommendations are given on the actions that should be taken and the allocation of duties to individuals. It is recommended that the duty of ensuring that all the relevant procedures and checks are carried out be given to one individual known as the "Temporary Works Co-ordinator"