CPD: Management of temporary works

A dedicated manager of temporary works is often overlooked on smaller schemes. But the project could suffer as a result, argues the HSE’s Phil Deebank

The results of the CIOB’s survey and report – Health and Safety in the Construction Industry 2009 – included a recommendation that more consideration in safety standards be given to temporary works. The survey results suggest there is more awareness and experience of temporary works on higher-value projects. While 78% of survey respondents working on projects worth more than £15m stated that a temporary works co-ordinator (TWC) was formally appointed, this dropped to just 23.9% for projects worth £200,000 or less.

Temporary works are likely to form a key part of any construction project. British Standard BS 5975: 2008 – Code of Practice for Temporary Works Procedures and the Permissible Stress Design of Falsework – defines temporary works as “parts of the work 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”.

In practice, temporary works will range from the provision of site hoardings or fencing, foundations and support to site cabins and accommodation units, trench and excavation supports, scaffolding, support of construction plant, through to the provision of falsework and formwork for reinforced concrete structures, temporary bracing and propping of structural frames under construction and temporary propping, shoring, facade retention and needling works for refurbishment. Temporary works can even include demolition projects.

Effective, safe and perhaps imaginatively designed temporary works solutions can bring significant benefit and add value to projects in terms of safety, certainty, productivity, efficiency, quality, completion times and cost.

On the other hand, poorly planned, designed, constructed, supervised and managed temporary works leave projects open to risks such as injuries or fatalities, the failure or collapse of both temporary and permanent works, damage to adjacent premises, and the consequent delays and increased costs.

Poor standards

In recent years, concerns regarding the poor management and design of temporary works structures have been raised in various publications from the HSE and the ICE’s Standing Committee on Structural Safety. The CIOB’s Health and Safety in the Construction Industry 2009 report again suggests poor standards in the effective management of temporary works, particularly on smaller sites.

The collapse of a major bridge falsework structure over the River Loddon near Reading in 1972 prompted the government of the time to set up the Advisory Committee on Falsework to consider various aspects related to the management, supervision and design of falsework structures. The committee, chaired by Dr S Bragg of Brunel University, considered evidence regarding a wide range of falsework failures relating to building and civil engineering structures in the UK and abroad. The findings and recommendations of the committee were published in 1976, and became commonly known as the Bragg Report.

Among the recommendations was the need for relevant procedures and checks for the safe procurement, design, construction and loading of falsework to be given to one individual on site: the temporary works co-ordinator, or TWC.

BS 5975 was first published in 1982, entitled Code of Practice for Falsework with a second edition published in 1996. Both of these earlier editions adopted the term “falsework co-ordinator” as the procedures section of the standard was solely limited to falsework.

But in BS 5975: 2008, the section on procedures was widened to cover the management of all temporary works (in building and civil engineering) and therefore reverted to the term of temporary works co-ordinator as originally proposed in the Bragg Report.

The Construction (Design and Management) Regulations 2007 and the associated Approved Code of Practice are particularly relevant to the design and provision of safe temporary works on site. The interpretation of “structure” as defined by the regulations includes “... (b) any formwork, falsework, scaffold or other structure designed or used to provide support or means of access during construction work... “

Specific areas of temporary works are also addressed in Part 4 of the CDM 2007 regulations, including: good order and site security; stability of structures; demolition or dismantling; excavations; and reports of inspections.

Some of these regulations set standards of compliance above what is deemed “reasonably practicable”. For example, regulation 28(2) – Stability of structures, states: “Any buttress temporary support or temporary structure must be of such design and so installed and maintained as to withstand any foreseeable loads which may be imposed on it, and must only be used for the purposes for which it is so designed installed and maintained.”

Specific reference to temporary works is made in the CDM 2007 Approved Code of Practice: Managing Health and Safety in Construction. This describes how arrangements for managing and controlling temporary works should be covered in the “construction phase plan”.

Contractor responsibilities

While the design and procurement of the completed permanent works is normally dealt with by design consultancies – ie architects, consulting engineers or surveyors – the design of temporary works structures may be carried out by principal contractors, contractors, specialist sub-contractors and equipment suppliers. In some cases, consulting engineers specialising in temporary works design may provide design services for both contractors
and suppliers.

Where a principal contractor, contractor, designer or supplier is involved in temporary works, the organisation should appoint a senior person responsible for establishing and implementing a “temporary works procedure”.

The items that need to be addressed in this (according to clause 6.3.1 of BS 5975:2008 ) are as follows:

•           
Appointment of a TWC

•           
On larger sites, appointment of temporary works supervisors

•           
Assessing/ensuring competence of design and site-based staff responsible for temporary works

•           
Preparation of adequate design briefs

•           
The design (including calculations, sketches, drawings, specifications and design risk assessments)

•           
Where appropriate, the designers’ method statement

•           
Independent checking of the design

•           
Issue of design check certificates

•           
Procurement of temporary works materials and equipment (in accordance with the designer’s specification)

•           
Site control of erection, use, maintenance and dismantling of temporary works

•           
Checking of erected temporary works (and control of use) to ensure compliance with the design

•           
The issue of the “permit to load” and “permit to dismantle” where required.

The temporary works co-ordinator

The TWC takes lead responsibility for ensuring that the organisational/project procedures for the control of temporary works are properly implemented on site. Usually, the TWC will be employed by the principal contractor.

The TWC has a potentially onerous and demanding role. If, for any reason, the TWC is under undue pressure (for example to achieve production targets) then they should be able to seek assistance from the designated person responsible for establishing the temporary works procedure.

According to clause 7.2.5 of BS 5975:2008, the TWC should:

•           
Co-ordinate all temporary works activities

•           
Ensure that various responsibilities have been allocated and accepted (eg designers, design checkers, erectors, site supervisors)

•           
Ensure that risks identified at design stage, as well as assumed construction methods and loading constraints, are incorporated into the temporary works design brief.

•           
Ensure that the temporary works design is satisfactory

•           
Ensure that a design check is carried out, covering concept, structural adequacy and compliance with the design brief

•           
Ensure the design is made available to relevant parties

•           
Register or record all drawings, calculation and other relevant documents relating to the final design

•           
Ensure that those responsible for on-site supervision receive full details of the design, including any limitations and guidance notes

•           
Ensure that risk assessments and guidance notes are prepared covering the safe erection and dismantling sequence

•           
Make checks at appropriate stages during construction of temporary works

•           
Ensure that appropriate maintenance is carried out to temporary works (eg to facade retention structures)

•           
After a final erection check, issue the permit to load

•           
Once the permanent works have attained adequate strength, issue formal permission to dismantle the temporary works and specify any relevant sequence

•           
Ensure the temporary works are dismantled in accordance with a defined procedure.

The TWC must be competent enough to discharge their duties. While a competent civil/structural engineer may have the desired competence level to act as a TWC, the supply of civil/structural engineers is clearly not sufficient to provide cover at that level for all projects. Those with first degrees or diplomas in construction management or building could, with appropriate training and experience, be considered as suitable for the role.

TWCs from a vocational background could possibly find themselves out of their depth when dealing with temporary works schemes. The Bragg Report suggested that on smaller sites the role of TWC might be fulfilled by a site agent. But the report also suggested a TWC could be contracted in, possibly on a visiting basis. Clearly, the construction industry of 2010 is considerably different from the 1970s with regard to procurement routes, organisation and the different plant and temporary works equipment used.

TWCs should be provided with appropriate training. Courses and training programmes for those who do not have an appropriate background in civil/structural engineering may need to be specially tailored to accommodate their needs.

The TWC will normally need the support of experienced temporary works designers, likely to be experienced chartered civil or structural engineers,
in drawing up adequate design briefs, deciding upon design checking requirements for specific temporary works structures and providing general advice on temporary works matters.

To this end, TWCs should have access to either an in-house temporary works design office or department, or a dedicated consulting engineer specialising in temporary works design. This support might be particularly important where elements of design work are to be undertaken by specialist contractors and suppliers

Phil Deebank CEng MICE, CMIOSH is a principal specialist inspector (construction engineering) with the Health and Safety Executive’s Field Operations Directorate. The information and opinions in this article do not necessarily reflect the views or policy of the HSE.

Failure to co-ordinate temporary works led to a major scaffold collapse in Milton Keynes, April 2006

Failure to co-ordinate temporary works led to use of needle beams for major structural work

Failure to co-ordinate temporary works led to temporary supports and access to a mast-climbing platform

Case study: aluminium falsework and formwork for a concrete slab.

In this example, temporary works designers, temporary works co-ordinators and the structural engineers for the permanent works would all need to be involved.

In all falsework, there is a requirement that, to ensure stability, it should be designed to resist a minimum lateral (horizontal) load at the top. This includes the wind load on the formwork and associated falsework elements.

In practice, the required stability is achieved by strutting or tying the top of the falsework to the existing permanent structure at the level of the formwork (top -restrained) or otherwise by providing bracing through the height of the falsework structure to the supporting surface (free-standing).

In this example, the formwork (2 and 5) consists of a proprietary falsework system incorporating its own formwork panel system (2). This will commonly be designed by a temporary works designer working for the equipment supplier, but could be designed by others as a package or with separate organisations designing the formwork and falsework.

If the falsework is to be designed as top-restrained, the formwork and the supporting falsework beams will need to be adequate to transfer the required lateral loads to the adjacent structure. Here, to transfer the horizontal loads, the formwork panels and make up pieces (2 and 5) are butted up to and cut in around the existing structure.

The temporary works designers will need to ensure the formwork and supporting falsework is stable under wind load (1), including the effect of wind uplift. They will also need to decide if the falsework (3 and 4) is to be designed as top-restrained or free-standing. Most modern aluminium falsework will be top-restrained.

The overall design of the temporary works will need to ensure that relevant elements of the permanent works, including columns (8) and walls (9), are strong and stiff enough to transfer lateral loads from the formwork and associated falsework.

An assessment of the capability of the permanent works to resist these loads will generally be outside the scope of temporary works designers employed by proprietary equipment suppliers. This will most likely require the input of a temporary works designer employed by the structural frame contractor or the principal contractor, in conjunction with structural engineers responsible for the permanent structure.

The structural floor slab (10) supporting the falsework structure will need to be adequate to support the imposed load from the falsework above.

Again, an assessment of the strength and structural behaviour of the floor slab will require input from the structural frame contractor or principal contractor and liaison with the structural engineers responsible for the permanent works.

If service voids or other openings are in the supporting floor slabs, falsework legs or props may need to be supported on falsework beams (6).

Safe means of access, including suitably designed edge protection (7), should be designed as part of the overall temporary works.

CPD test paper

Management of temporary works

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