Temporary Works (in Construction)

We all know and understand that the CDM 2015 (Construction, Design and Management) regulations have a huge impact on Health and Safety within Construction. This includes workers on site, members of the public who may be impacted by the works as well as other supporting operatives. However, CDM itself does not cover 'Temporary Works'. Temporary Works (often referred to as TW's) can be equally dangerous, especially if not planned and managed appropriately.

Temporary works are an 'enabler', it is these types of construction works that support the main construction works. The primary purpose of temporary works is to ensure the stability and safety of a construction site, workers, and the general public during the building process. Temporary works help distribute loads, prevent collapses, and manage construction-related risks.

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.

The law states that any temporary structure must be designed, installed, and maintained to withstand any foreseeable loads which may be imposed on it and that it be only used for the purposes for which it was designed, installed, and maintained.

Additionally, temporary works such as scaffolding, excavations, cofferdams and caissons must be inspected by a competent person on a regular basis. It must also be noted that on any construction site there has to be evidence to show intention to prevent risks by establishing a chain of responsibility linking all the parties involved.

What You Need To Know

Temporary works provide an engineered solution that is used to support or protect either a structure during construction, an item of plant or equipment, the sides of an excavation during construction operations or to provide access. Temporary works need to be planned and managed.

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.

Temporary works to provide structural support include:

• Shoring for excavations
• Propping for walls and floors
• Falsework for above ground concrete pours
• Scaffolds for access
• Haul roads and working platforms for plant including cranes
• Permanent works used for temporary purposes during construction

Temporary works on a construction site also include:

• Site fencing and hoarding
• Welfare and office units
• Earthworks, including stockpiles, that will be removed later

Currently, there are no specific legal requirements about how temporary works should be managed; each organisation can choose how they arrange and manage safety on site.

Temporary Works Coordinator

An effective way of managing temporary works it is recommended to appoint a Temporary Works Coordinator (TWC) to ensure suitable designs are prepared, checked, and correctly erected on site. The TWC should be formally appointed and have adequate authority to carry out the role, including stopping the work if it is not satisfactory. The TWC may also need to advise on build sequence, systems of work and equipment so that other activity does not damage or compromise the temporary works.

On a complex project this person is often a chartered civil or structural engineer with relevant experience and training and based on site. On a simpler job the main contractor may take on this role and seek advice as needed from an engineer.

Temporary Works Equipment

Equipment manufacturers' instructions must be followed in the selection and use of temporary support. In all but the simplest situations a design, including calculations, will be needed for the temporary works. In more complex works the design will also need to be checked by an independent party.

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"

Temporary Works 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 Temporary Works Coordinator. 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 suggested below.

Categories of Design Check (taken from BS 5975)

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.

Smaller Contractors - Temporary Works Management Arrangements

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 simplest temporary works. There should be clear evidence that appropriate external expertise has been engaged. This includes obtaining the services of a suitably competent Temporary Works Coordinator 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 Temporary Works Coordinator and Designer roles to be carried out by the same person.

Useful Links:

• HSE - Temporary Works, what you need to know
• Temporary Works Forum - BS 5975: 2019