Shaping and sharing best practice in construction health and safety risk management

Transcription

1 Shaping and sharing best practice in construction health and safety risk management JUNE 13 Designing Buildings with Safety at Height in Mind SUMMARY This Practice Note makes reference to the important and highly relevant recently published British Standard that defines the expected practice in handling safety at height issues during the building design process, BS 8560: 2012 Code of Practice for the Design of Buildings incorporating Safe work at Height. The purpose of this Practice Note is to explain the key principles behind the responsibilities imposed by the CDM Regulations 2007, and to outline the expected practice contained within the British Standard. 1.0 Introduction The CDM Regulations require us to consider all aspects of safety when designing buildings. Our responsibility is to consider the safe construction, operation, maintenance, and demolition of all that we design, and to consider the impact of each design decision on the overall safety of our project. No single aspect exposes more safety issues than the need for construction or maintenance work at height. There are specific duties imposed, by the Work at Height Regulations, in relation to the management of the work at height hazards, the manner in which work at height is considered, and the way the control measures are selected. Designers manage many competing factors during the design phases of a project. In the early stages the primary Client needs are captured and the form develops. This can be influenced by many factors such as function, location, aesthetics, cost, local planning, and also by regulatory factors such as fire, environment, and sustainability. Two key areas must also be considered, Buildability and Maintainability, and both have significant impact on the nature and extent of the work at height required. The time to consider these issues, and how best the work at height can be effectively managed, is at the early design stage. All too often consideration is put off until later in the design process frequently resulting in a limited range of options and higher cost solutions. Early consideration of the extent, nature, duration, and frequency of any work at height required, allows appropriate equipment and methods to be selected, to construct, clean, maintain, and repair the building. These can then be incorporated into the initial design and more efficiently accommodated within the project. Whilst these principles are explained using buildings and building terminology, buildings are defined as any man-made object and these principles are equally applicable to all other areas of construction activity. ISSN X

2 2.0 Established principles Many of the design decisions can result in the need to consider work at height. The primary hazards associated with this work mostly involve falls threatening the worker and falling objects threatening others. The basic hazard management principles should first be applied. Can the need to work at height be avoided, if not, can we prevent the falls occurring, if not, can we mitigate the consequences of any falls that could occur? The Work at Height Regulations offer more detail, by also recognising:- that collective control measures (that protect everyone) are superior to personal measures (that only protect an individual), that passive measures (that require no action on the part of those protected) are more effective than active ones (that require the user to act in a specific way), that permanent measures (that form part of the permanent works) tend to be better managed than temporary ones. If we combine these requirements, we establish an order of increasing desirability in relation to the selection of control measures for the management of work at height. This is often termed the Work at Height hierarchy, and it should be used to guide and inform the selection of the various, frequently complex, alternative solutions to work at height problems within the design decision making process. Increasing Desirability 1. Avoid the need to work at height. Use remote controlled solutions like robots, cameras, reach and wash poles. Modularise, pre-fix, and pre-assemble. Consider remote lighting like fibre optics or reflecting surfaces. 2. Collectively prevent falls. Use parapets, guard rails, cradles, or other designed in permanent features, then consider scaffolding, MEWPs*, or other temporary measures. (no fragile surfaces). 3. Personally prevent falls. Use pulpit steps, rope access, or roof mounted anchorage systems designed to prevent the user getting to a potential fall position (no fragile surfaces). 4. Collectively minimise the height and consequence of falls, Use equipment fitted close to the faller, like permanent or temporary safety nets (rarely accommodated within a design). 5. Personally minimise the height and consequence of falls. Use permanent or temporary harness and lanyard solutions, positioned in such way as to minimise the fall height. 6. Collectively minimise the consequence of falls. Use remote soft landing systems like airbags and bean bags (rarely considered at design). 7. Personally minimise the consequence of falls. Use personal injury reduction measures like inflating suits. 8. Provide no fall protection to an individual, by using steps, hop-ups, stilts. 9. Provide no fall protection to all, by leaving unguarded edges, stages, platforms, loading docks. * Mobile Elevating Work Platforms All work at height control measures, whether designed in or reactively selected, will fall into one of these nine categories. The Designer s intention should be to use measures as high up the desirability scale as possible, whilst balancing and incorporating the many other design issues competing for attention. Despite being driven by Regulation, this selection becomes a matter of Designer judgement.

3 3.0 How to apply these principles to the building design process All manner of design decisions impact the need to work at height and extent of that work. High rise buildings will clearly require more work at height than low rise buildings, and the shape and form of the building being considered will ease or complicate the access options and alternatives. The British Standard compares the impact that the general building shape can have on the complexity of the facade access method. Inclined facades, stepped facades, curved and tapered facades, and protruding features, all complicate the method of access for cleaning and maintenance. Equally significant is the impact that the surrounding area will have on access options and alternatives. Steep slopes adjacent to the building, soft verges, or rivers, roads, and railways, all restrict or limit the access equipment choices. The materials selected within a building can also have significant impact on the need to work at height, and the duration and scale of the height safety hazards. The façade materials, extent of glazing, and method of installation and support all have a bearing on the work at height. Externally fitted curtain walling may be installed from cradles, mast climbers, or MEWPs, while alternative solutions using pre-formed cladding panels might be installed from within the building by accessing the open slab edge and using mechanical manipulators. Each method has their height safety issues, and associated pros and cons, both from an initial installation perspective, and for subsequent maintenance and future replacement. Self-cleaning materials, long-life paints, and the choice of light fittings/luminaire type, can reduce the frequency of maintenance access. Non-fragile materials in roof lights and service covers can remove the fall-through hazard in areas of roof requiring access. The incorporation of parapets and guard rails within the initial design can effectively manage fall hazards both during the construction process and for maintenance within the finished building. 4.0 Application of Desirability 4.1 Avoid Clearly the most desirable solution is to avoid the need to work at height. Whilst this might seem impractical there is an increasing array of technical solutions that can be used to avoid working at height. Façade cleaning robots on high rise buildings, and reach and wash ground level systems both avoid the need to work at height. Inspection requirements are frequently interpreted as the need for the provision of an access system, however improvements in image quality and remote controlled support solutions make inspection using cameras a real alternative. The use of fibre optics to transfer light from an accessible source avoids the need for work at height to maintain the light, in the same way as low level spot lights bounced off high level reflectors, or pivoting lamp standards. All manner of modular construction, pre-assembly, and prefitting can reduce the need to work at height, or the extent and duration of that work. Image courtesy of Traxoid Automations Pvt Ltd Image courtesy of Cleanscene

4 4.0 Application of Desirability continued 4.2 Collective Prevention Parapets and guard-rails, with no fragile materials, offer permanent fall prevention to all who need to access the area during the operation of the building or for maintenance. Careful design and programming can also offer this benefit to those constructing the project, to significant commercial advantage. Cradles and Building Maintenance Units (BMUs) offer a similar level of collective prevention for façade access, although consideration could be given to their capacity to replace façade elements as well as to support the cleaning and inspection function. Temporary collective prevention measures include scaffolding, MEWPs, edge protection, towers, and safety decks. The provision for edge protection can be designed into permanent works, and careful, detailed design can ensure that adjustment of any temporary works are minimised between trades. Clients frequently pay between three and five times for temporary edge protection around the perimeter of a project. Image courtesy of Kingspan Insulated Panels 4.3 Personal Prevention This is often termed restraint as, correctly set up and used, the worker is restrained from access to a position from which a fall can occur. Many systems are compromised in terms of layout, loading, and the presence of fragile surfaces, and frequently the user equipment specified is inadequate, or requires a high level of competence and experience to operate correctly. Rope access is also a form of personal fall prevention, as the worker is suspended and thus prevented from falling. Support points and rails for rope access use can be advantageously incorporated into a building, however they attract surprisingly high load capacity requirements in accident loads and for rescue needs, and are frequently under specified. 4.4 Collective minimise height and consequence The mainstay of this area is the temporary use of safety nets. They offer collective planar safety to activities such as sheeting roofs, or laying metal decking. They are rarely considered during the design of a building, although some thought to their support could be beneficial. 4.5 Personal minimise height and consequence A harness and lanyard solution that permits the user to fall, but then minimises the fall height and the consequence. All solutions within this area must employ some form of energy absorption, to limit the loads on the worker and the building anchor. They must also incorporate a site based rescue method for anyone using them, an aspect that is often overlooked when specifying window cleaning anchors. There may be rare situations in which the designer chooses even less desirable solutions however, for the majority of new buildings, the access methods incorporated into the design should be from the more desirable levels within the hierarchy. Image courtesy of

5 5.0 Code of Practice for the Design of Buildings incorporating Safe Work at Height BS 8560: 2012 In terms of the design decisions that impact the extent of work at height required on a project, the Standard uses a series of generic sketches to explain the pros and cons of the various access opportunities and decisions. The Standard first looks at roof access, and starts by posing the important question, do you really need access onto the roof? It is far more desirable to avoid the need to access the roof and to inspect from afar. If work is occasionally required, significant temporary works on a reactive basis can offer a far more affordable solution than the constant maintenance of an access system that is rarely needed. The Standard then looks at the desirability of the access control measures that can be used in the various roof zones. It mentions the benefit of making rainwater outlets and gutters easy to access for clearing, and the importance of nonfragile materials for roof-lights within an area that needs access. It also applies the desirability criteria to the edge of the roof, showing that permanent parapets are more desirable than temporary guardrails, and that both are preferable to an anchorage cable system. All too often a well-intentioned perimeter cable system might have been specified to allow access to clear the perimeter gutters. A more desirable solution from both a cost and a work at height perspective might have been to provide perimeter access using a temporary MEWP. If that solution is rejected for some other reason, the cable system is immediately vulnerable to some value engineering at tender and is frequently reduced to a spine system and long adjustable anchorage line. This might be suitable for an experienced work at height technician, but is it a reasonable set of work equipment for a general building maintenance worker who will only use it occasionally and reactively. The Standard then looks at the various access methods for low rise pitched roofs, ground and floor based temporary equipment, collective and permanent building mounted access equipment, and then personal permanent building mounted access equipment. This system is also frequently compromised by the subsequent inclusion of roof-lights within the work area. These roof-lights become increasingly fragile as the building ages, and the equipment specified for use is frequently termed fall prevention (or restraint) equipment, and is wholly unsuitable to arrest a fall. Images courtesy of and BSi from BS 8560 : 2012 The desirability criteria should be applied to the full set of design requirements to guide and inform the decision making on each individual project.

6 6.0 Who should do what, and when Perhaps the single most influential aspect is the timing of design decisions. The earlier that these work at height aspects are considered, the more easily good practice can be accommodated within the design. BS 8560, follows the phases and stages of building design, and clearly recommends who should be doing what at each stage. The Standard advocates the involvement of the CDM-C, or other person responsible for the overall design phase co-ordination, at or before the concept stage, depending on the experience of the lead designer. The Standard stresses the need for the design team to understand construction constraints and maintenance issues at the preparation of the design brief, and to seek specialist consultant support and guidance on the downstream consequences of their early decision making on work at height issues. The team should identify those construction, maintenance, and access needs within the design that will involve work at height, and manage them by applying the desirability principles above. This will be an iterative and complex process, as many aspects are interlinked. The objective is to strike as desirable a balance as possible between the conflicting project needs. An example of this early stage need would be the provision of an aircraft warning light on a very tall structure. The need to provide such a light is well understood, but the detail concerning when to install the light at the top of the structure, and how to subsequently maintain it, can frequently add substantial and unnecessary cost and safety concern to the construction process and the future maintenance. Much of the British Standard focuses on maintenance access, and the impact of design decisions on the frequency and scale of the maintenance need. When positioning plant, for instance, consideration must be given to the means of access (lift, ramp, stair, or ladder), what must be taken there, and what other facilities must be available to complete the maintenance work. (E.g. it might be difficult to carry a replacement lift motor up a vertical ladder to a roof-mounted lift motor room). The involvement of the future facilities management team, or an adviser, is also recommended at this stage. It is important to protect the work at height design decisions from review and value engineering, during the design development and the technical phases of the design. There are some recording tools within the Standard that can support the design phase co-ordinator in this effort. 7.0 Communication and Contract As the design develops and details are required, the design team will grow, as will the complexity and interdependence of all aspects of the design. Increasingly the detail within the design will be provided by the specialist consultant, Designer, contractor. The popularity of package contracting has fed this increase, resulting in the detail within a design only being known once the specialist installer has been appointed. Communication of these details between packages is vital to maximise collaboration and minimise confrontation. Early appointment of these specialist packages will aid the visibility and communication of these details, so that they can be taken into account within the other packages. Equally the development of longer term relationships within design teams, and repeat business, will cascade specialist details and the solutions and methods in use at the current time. On the larger projects the use of Building Information Modelling (BIM) to capture and communicate information and record decisions aids this process and also feeds the development of the health and safety file. On smaller projects drawing icons can be helpfully used to tag, flag, and record issues, and communicate decisions or draw attention to safety issues that are unresolved.

7 8.0 Tools within the Standard to support the design phase co-ordinator There are a number of suggested tools within the British Standard recommendations that can be used by the design phase co-ordinator in support of their role and contribution. The Project Information Table from Annex A is designed to record key aspects of a project and the impact that they might have on the design options and decisions. This table encourages the co-ordinator to capture this key information, relating to work at height, and to record the influences and design options that flow from it, and the rationalisation behind the design decision. This allows the design team to readily record their thinking and also see the impact and range of consequences linked to a change within a given design decision. This table could ensure that a broader range of consequences are preconsidered before a design decision is changed or reversed, and can also be used to protect a project from unsuitable value engineering. Another suggested tool from within the Standard is the Options Matrix in Annex C. This is designed to assist the design team in analysing the benefits of frequently conflicting constraints and demands within a design brief, and the associated options and alternatives. It serves to record options, and the thinking behind decisions, in a visual and easily communicated way. 9.0 General Conclusion It is our responsibility to design everything with safety in mind, and certainly to consider the work at height issues when designing buildings. We need to consider how the building is going to be built and maintained, whilst making the design decisions about what the building will look like and how it will function. We have duties and responsibilities within the various Regulations that we need to consider, and we have Standards and Codes of Practice that we can use to inform and guide our decisions. We should not incorporate significant, foreseeable, hazards into our designs, and this includes the hazards associated with work at height. So far as is reasonably practicable, we should avoid the need to work at height. Where we cannot do this we should prevent falls, using collective, passive measures before personal, active ones, and permanent measures before temporary ones. Where prevention is impractical, we should design measures into the building that minimise the potential fall height and the consequence of any fall, again selecting collective, passive measures before personal, active ones. If our selected work at height control measures can permit a fall to occur, the work method must incorporate a site based rescue method. The important messages within this area are not prescriptive ones, but rather ones of informed and balanced judgement.

8 APS would like to thank Barney Green of Higher Safety for his help in compiling this Practice Note; the manufacturers for the use of their product images and BSi for the drawings from the Standard. TO MEET THE REQUIREMENTS OF THE EQUALITY ACT 2010, THis practice note CAN BE ACCESSED IN ALTERNATIVE FORMATS BY CONTACTING APS. Copyright The ownership of copyright of this material is asserted by the Association for Project Safety Ltd. Any infringements of copyright may be actionable by the Association. Status of this Guidance This Practice Note has been prepared to provide general advice. APS does not offer this document as legal advice for any particular situation, as each project will be different. If you need advice on the interpretation of the regulations as they apply to a specific situation you should take advice from a suitably qualified person. Association for Project Safety 5 New Mart Place Edinburgh EH14 1RW T F E info@aps.org.uk