CPD Seminars part two
CPD Seminars > CPD Seminars part two
The CDM Regulations and how designers can help to avoid or reduce health and safety risks in construction – including when specifying gypsum products and related systems
Firstly, a few words about 'The Management of Health & Safety at Work Regulations 1992'.
These Regulations already place general duties on employers and the self-employed to make effective arrangements for managing health and safety. These Regulations also make more explicit the requirements of the relevant section of the Health and Safety at Work etc. Act 1974.
Under the management of Health and Safety at Work Regulations, designers, irrespective of whether they be employers or self-employed persons, have a duty to assess the risks arising from their work. However, this assessment doesn't necessarily consider the effects that the design work may have on the health and safety of those who subsequently build the structure.
A summary of the Management of Health and Safety at Work Regulations is given in Appendix 1 of the Approved Code of Practice L54 which relates to the CDM Regulations.
The CDM Regulations place new duties on designers to rethink their approach to health and safety and to ensure, as far as is reasonably practicable, projects are designed to avoid or reduce health and safety risks while they are being built and subsequently maintained.
Where risks remain, they have to be stated to enable reliable performance by a competent contractor.
Designers, of course, have always had to make themselves aware of the risks associated with certain types of work and to design, specify and cost accordingly – high risk work such as demolishing a tall structure or providing temporary supports to an existing one; building on contaminated land; or where there may be subsidence risks; removing asbestos.
However, the health and safety risks involved in many other types of work have been less widely appreciated and consequently the opportunities to reduce these risks at the design stage have been lost.
The consequences of a designer not designing a building which avoids or reduces health and safety risks could be very serious. Apart from the legal implications, the bad publicity from HSE investigations could be very damaging.
Designers have often left the responsibility for most health and safety matters with the main contractor. Although having said that, the CDM Regulations do not place extra duties on designers or the management of health and safety on site during construction – this remains the responsibility of the contractors.
We referred to the pre-tender health and safety plan in Seminar One. The planning supervisor has to ensure that the plan is prepared before the tendering process and brings together the health and safety information obtained from the client and designers and this helps the clients to appoint a principal contractor.
It's very important that clients, and planning supervisors who advise them, allow sufficient time for principal contractors to develop health and safety plans before construction work starts.
The principal contractor will need to update the construction phase plan as work progresses and to ensure that, as far as is reasonably practicable, every contractor complies with any rules contained in the health and safety plan.
The Approved Code of Practice L54 provides practical guidance on compliance with the provisions of the CDM Regulations and other relevant health and safety at work legislation which is applicable to construction projects.
The publication entitled 'Designing for Health and Safety in Construction' provides detailed guidance on the CDM Regulations for designers involved in construction work. Everyone involved in the design process should familiarise themselves with the guidance given in this book.
The CDM Regulations, together with the associated Code of Practice L54, and other publications such as the designers guide represent a concerted effort to reduce the unacceptable high rates of death, injury and ill health which bedevil the construction industry.
For the first time, clear duties are now imposed on everyone in the construction process, from the client to sub-contractor to improve health and safety on site. Health and safety must now be taken into account from conception of a construction project right through to completion.
Apparently, those who spend their working lives on construction sites have a 1 in 300 chance of being killed. Workers are over fives times more likely to be killed on a construction site than in a factory.
So why is the designer so important? Research carried out by the Health and Safety Executive showed that about a third of accidents on site could be eliminated by designer change, and that a further third could have been prevented by improved planning before construction work commenced.
Designers play a key role in a construction projects. They may be the only people able to make decisions that will eliminate or reduce foreseeable risks.
By designing to avoid or reduce health and safety risks, designers are helping to create an environment which assists contractors in managing the site works – whether it be during the construction of a new structure or during the subsequent repair, maintenance and possible demolition.
Unfortunately, the Association of Planning Supervisors, which is the largest organisation for planning supervisors in the UK, has found that there is now substantial evidence that many designers are not undertaking their CDM responsibilities effectively – particularly in not making clients sufficiently aware of their duties.
Designers are the key to making clients aware of their duties under CDM. For example, explaining to the client the importance of an early appointment of the planning supervisor.
Experience is also showing that designers are not sufficiently altering their designs to take account of health and safety risks. Very often, risk assessments are only being made after the design is completed.
The Approved Code of Practice L54 refers to the designer's responsibility as being:
"Designers must design in a way which avoids, reduces, or controls risks to health and safety as far as is reasonably practicable so that projects they design can be constructed and maintained safely. Where risks remain, they have to be stated to the extent necessary to enable reliable performance by a competent contractor".
Designers should ensure, as far as is reasonably practicable, that the health and safety of those who are going to construct, maintain or repair a structure is considered during the design process. If they don't they make it difficult for a contractor to devise a safe system of work. Contractors have to manage the risks on site, but designers can often eliminate or reduce them in the first place.
The design, and we'll have a look at the definition of 'design' very shortly, must include adequate information about any aspect of the structure or materials which might affect the health and safety of any person at any time.
Designers develop from initial concepts through to a detailed specification. At each stage, designers form all disciplines have a contribution to make in avoiding or reducing health and safety risks.
Designers may need to work with other professionals such as specialist surveyors and engineers. Communication between designers and contractors at an early stage should also be encouraged.
Unfortunately, experience is showing that designers' knowledge of health and safety is limited. There is a need for more training to be included in university courses and from more frequent visits to site to learn about the link between design, construction and health and safety risks.
Discussions with manufacturers and suppliers of building products and systems is also recommended. For example, to discuss problems which certain products may cause – such as components of excessive weight.
Recommendations could be obtained, for example, on the use of lightweight metal framed systems and how, in addition to speed of assembly, they can considerably reduce the injuries associated with heavy, traditional construction. Metal framed systems that could be used, for example, as partitions or suspended ceilings.
One of the main advantages of steel framed buildings is that they provide off-site prefabrication – and reduce on-site installation injuries.
Advice could be sought on ways of reducing the large amounts of dust which can be produced on site.
Time doesn't allow us to consider all of the CDM requirements on the designer but these are given in Regulation 13 as reproduced in the Approved Code of Practice L54.
It's very important that designers make themselves aware of Regulation 13 and comply with the requirements.
The definitions of 'design' and 'designer' are given in the Code of Practice:
'Design in relation to any structure includes drawing, design details, specification, and bill of quantities (including specification of articles or substances) in relation to the structure.
'Designer' means any person who carries on a trade, business or other undertaking in connection with which he:
1. prepares a design, or
2. arranges for any person under his control (including, where he is an employer, any employee of his) to prepare a design, relating to a structure or part of a structure.
The terms 'design' and 'designer', therefore, have a very broad meaning in the Regulations. Anything which is designed makes the author a designer. Even a drawing on the back of an envelope would be classed as a design.
It's very important to be aware that the CDM Regulations apply to any design work, no matter what size of type of construction work is, and no matter how long the work lasts and how many workers are involved on site.
One of the client's main duties is to select and appoint, as soon as possible, a competent planning supervisor and to appoint a principal contractor. The planning supervisor has the overall responsibility for co-ordinating the health and safety aspects of the design and planning phase.
There are conflicting opinions on whether the planning supervisor should be a multi-disciplinary team or an individual. It's argued that individual planning supervisors cannot be competent to fulfil the variety of duties under CDM.
One of the designer's responsibilities is to co-operate with the planning supervisor so that health and safety information can be passed on and incorporated in the pre-tender stage health and safety plan. The planning supervisor has to ensure that the pre-tender plan is prepared. This plan is then made available to contractors who are tendering.
Guidance on the pre-tender stage health and safety plan is given in HSE information sheet No. 42.
Where health and safety risks are not obvious from the design documents, the designer must provide additional information to all relevant parties.
As we said earlier, the successful principal contractor is required to develop the pre-tender plan before work starts on site. Guidance on what issues could be include in the health and safety plan for the construction phase is given in the HSE information sheet No. 43.
The planning supervisor must also ensure, during the construction phase, that a health and safety file is prepared and that this is given to the client at the end of a project. This is a record of information which tells all of those responsible for the structure of risks that have to be managed during any future design, maintenance or demolition of the structure. Guidance on the health and safety file is given in the HSE information sheet No. 44.
A summary of the designer's key duties, as far as they are reasonably practicable, is included in the HSE leaflet 'CDM Regulations – how the Regulations Affect You'.
Guidance on the duties of the designer is given in the HSE information sheet No. 41.
- Alert clients to their duties;
- Consider during the development of designs the hazards and risks which may arise to those constructing and maintaining the structure;
- Design to avoid health and safety risks so far as is reasonably practicable;
- Reduce risks at source if avoidance is not possible;
Consider measures which will protect all works if neither avoidance
nor reduction to a safety level is possible;
- Ensure that the design includes adequate information on health and safety;
- Pass this health and safety information onto the planning supervisor so that it can be included in the health and safety plan and ensure that it is given on drawings or in specifications etc;
- Co-operate with the planning supervisor and, where necessary, other designers involved in the project.
Let's now briefly discuss the GPDA and how the specification and use of the member companies' gypsum products and related systems can help the designer to avoid or reduce health and safety risks in construction.
The objective of the GPDA is 'to promote, encourage and develop the use of gypsum products'. On behalf of the Association's member companies I'd like to remind you, first of all, of the main types of gypsum products that are available.
Although gypsum is one of the world's most widely used building material, and is highly admired in its finished form, its use in the manufacture of an extensive range of pre-mixed building plasters, plasterboards and glass reinforced boards is not always recognised.
Gypsum products provide high standards of fire protection and can help to prevent loss of life and property.
Gypsum products and systems can also provide high standards of sound insulation in all types of building.
Thermal laminates are also available which can considerably improve the thermal insulation of building elements in new and existing buildings.
Pre-mixed gypsum plasters only require the addition of clean water to prepare them for use and they are the modern way of plastering many types of internal backgrounds including brick, block, concrete and plasterboard.
The use of sand and cement undercoats has now been largely superseded by gypsum plastering. Defects can often be experienced with sand and cement undercoats due to problems such as an incorrect grade of sand being used and/or insufficient time being allowed for the drying shrinkage before the gypsum finish is applied.
Gypsum plasters are also much lighter in weight and from a health and safety point of view this reduces the physical strain on the plasterer. Long term exposure to cement dust can also result in chronic chest disorders and cause dermatitis.
The choice of gypsum plaster depends on the required surface hardness or impact resistance and on the characteristics of the background, for example, whether the background is of low, medium or high suction and the type of key which it provides. Gypsum plasters are also available to satisfy specialist requirements such as X-Ray protection.
The vast majority of gypsum plastering is undertaken manually as a two coat hand applied method. One coat hand applied plasters are also available including one-coat gypsum plaster applied by a plaster projection machine.
As far as plasterboard is concerned, specifiers and users are increasingly recognising that plasterboard dry linings provide several distinct advantages. Since the mid 1980s plasterboard sales in Western Europe have risen by around 5% per year – which is well above the average for other building materials.
The wide range of plasterboard types and sizes means that there is a board for every wall or ceiling installation in all types of new build or renovation work. All gypsum plasterboards provide fire protection and sound insulation and other types are available to provide even higher levels if required.
In addition, there are boards which can provide moisture resistance; water vapour resistance; greater impact resistance; or even sound absorption. Plasterboards with decorative white faces or with raised panel surfaces are also available.
Laminates which incorporate gypsum boards and thermal insulating backings are used to provide insulated wall linings in new buildings and to upgrade the thermal insulation of walls and ceilings in existing buildings.
Thermal laminates can also be used to provide insulation at the rafter level of pitched roofs.
Laminates which incorporate moisture resistant glass reinforced gypsum lining can also produce higher standards of thermal insulation in situations such as exposed floors where the perimeters are open to the elements.
The boards can be used as a dry lining by following the manufacturer's recommendations for jointing and surface treatment.
Alternatively, the boards can be given a traditional plaster surface by using a finish coat plaster which is approximately 2mm thick – or a skim coat as it's often referred to.
Glass reinforced gypsum boards are also available which can provide high standards of fire protection at lower costs when compared with other specialist fire protective boards. The boards also offer a superior finish, higher impact and moisture resistance.
They can also be used to provide curved features.
If plasterboards or glass reinforced gypsum boards or laminates are screw fixed to lightweight metal framing systems, high performance wall lining can be provided which are easy and economical to install and which offer high performances.
High performance also applies to metal formed partitions; walls; and suspended ceilings.
A specifier no longer has to search for and put together different components and then obtain substantiation for the required performances. He can now consider selecting from the GPDA member companies' extensive ranges of tested systems and obtain whatever technical assistance is necessary to ensure that requirements are satisfied – including advice on the CDM regulations.
After that brief discussion on some of the main gypsum products that are available to the specifier, let's now discuss how the designer will have to take into account any health and safety risks which may arise in the use of these products on site.
If you were to ask any construction worker what is one of the most irritating activities on site, the chances are they would say "the amount of dust which is produced".
Is dust a hazard? Does it have the potential to cause harm?
The harmful affects of dust can range from skin irritation right through to cancer. The degree of risk is dependent upon the type of dust and amount of exposure. But it's important to remember that dust can cause injuries and be life threatening. We've already said that designers must eliminate or reduce risks before the contractors begin their work.
Gypsum dust is generated mainly from the handling, opening and mixing of bagged plaster and the cutting and sanding of plasterboards and glass reinforced gypsum boards.
Fortunately, the effects of exposure to gypsum dust are relatively minor and gypsum products are not classified as hazardous under the CHIP Regulations - The Chemicals (Hazard Information and Packaging for Supply) Regulations.
Gypsum is also not hazardous to health as defined in the COSHH Regulations. (The Control of Substances Hazardous to Health Regulations). Gypsum dust is a nuisance and irritant rather than a serious health hazard.
However, the HSE Report, 'Dust and Noise in the Construction Process' says "since long term consequences (of exposure to gypsum powders) are not yet fully understood, control of the possible risks should be practised".
The Health and Safety Executive stipulates Occupational Exposure Limits (OELs) for building materials. These limits refer to the respirable and inhalable airborne dust particles. The limits for gypsum products are unlikely to be exceeded except in poorly ventilated or confined spaces.
Because gypsum dust may irritate the respiratory system and also skin and eyes, all operations where gypsum dust may be generated should be kept to a minimum and carried out in well ventilated areas. If dust cannot be controlled, the wearing of dust masks and safety goggles is required. To avoid skin contact, protective gloves, overalls and footwear should be worn.
Although it will be the contractors' responsibility to ensure that these precautions are carried out on site, there are several ways in which the designer can further reduce the production of dust. Confined spaces, such as basements with inadequate ventilation, should be identified at the design stage so that suitable precautions may be included in the health and safety plan. This may require the provision of dust-extraction equipment or fitting dust bags to tools, etc.
Plasterboard dry lining can be specified so as to minimise the depth of chasing in masonry walls for pipes, conduits and cables. Cutting chases in masonry walls can produce large amounts of dust which can exceed exposure limits for both those undertaking the operation and others in the vicinity. Plasterboard dry linings screw fixed to lightweight, metal frameworks, which are virtually independent of the background, provide a wider cavity between the wall lining and the background. This facilitates the incorporation of services and eliminates the need for chasing.
With some independent lining systems, services can be installed behind the lining and accessed via a fire-rated access panel.
Other ways in which the designer can reduce the production of dust include providing storey heights which will allow plasterboard to be used as a wall lining without the need for cutting. This will reduce dust from cutting (and reduce wastage). The cutting of chases can also be considerably reduced if lightweight, plasterboard lined, metal framed partitions and walls are specified rather than masonry constructions. In addition to the excellent performances which they can provide, including high levels of fire resistance and sound insulation, metal stud partition and walls allow for very easy inclusion of services during construction.
Cut-outs in the webs of the studs can be used for routing electrical cables and other small services. These are normally installed after one side of the wall or partition is boarded. Cables should be protected by a conduit, or other suitable precautions taken, to prevent abrasion when the cables pass through the metal frame.
The metal sections of some partition systems have round or half-round cut-outs which can take rubber grommets to prevent abrasion of electrical cables. Metal fixing channel is installed between the studs to support recessed switch boxes and socket outlets. These may need to be backed with rock mineral wool to maintain a fire resistance requirement.
In accordance with the requirements for electrical installations, cables which are concealed within a wall or partition should be located at least 50mm from the surface opposite to where the electrical point, accessory or switchgear is positioned. If this is not possible, non-metallic sheathed cables should be installed vertically or horizontally within a 150mm wide zone from its connection to an electrical point, accessory or switchgear all of which are positioned on the wall or partition in straight runs. Alternatively, cables should be installed within 150mm of the top of the wall or partition or within 150mm of the junction between two adjacent walls or partitions.
If none of the requirements which we've looked at can be achieved, the concealed cable must incorporate a suitable earthed metallic covering or be enclosed in earthed conduit, trunking or ducting in accordance with BS 7671. Alternatively, mechanical protection should be used sufficient to prevent penetration of the cable by nails, screws, and other fixings.
The installation of electrical services should be carried out in accordance with BS 7671:1992 'Requirements for Electrical Installations'.
Where services such as ducts, fire dampers and access panels are required to penetrate a metal framed construction, their positions should be pre-determined so that a framed opening can be provided. All services, apart from those to be installed on the surface of the lining, should be independently supported from the structure. The duct or other similar service should be suitably fire stopped.
By designing service openings through which a larger number of services can pass, the number of individual service penetrations will be reduced. Service openings in drywall construction need to be fire-stopped by materials which have been tested to the European standard EN 1366-3.
In most situations, the services will be installed by contractors other than the dry lining contractor. So it's important that all relevant contractors are advised as to where and how their service penetrations should be made and maintained. Services which penetrate building elements need careful consideration to ensure that any required fire resistance is not impaired and that the services do not act as a means of spreading fire. Optimum sound insulation is also achieved only by airtight construction.
All service penetrations need to be adequately fire-stopped.
It's very important to use only those services and their installations which have been shown by fire test to be able to maintain the fire resistance of a construction.
Let's continue with the discussion on how the designer will have to take into account any health and safety risks which may arise in the use of gypsum products on site.
So that a gypsum board can be safely carried, on edge, by two men, the size and weight of the board need careful consideration – particularly if handling is in confined or very exposed situations. Risks to health and safety are also greater when working at height. Size and weight of the board are even more of a consideration if only one man is handling the board. The designer will also need to consider the possible use of mechanical handling methods not only to reduce the risk of manual handling injuries but also to speed up construction. Discussion with the planning supervisor can ensure that suitable provision is included in the health and safety plan.
The use of lightweight metal framed walls and partition will also reduce the manual handling problems associated with heavy building blocks. It's often wrongly assumed that it's only heavy, traditional material that can provide high standards of performance such as fire resistance and sound insulation.
Just for your information, as a result of research sponsored by the GPDA, the maximum bag weight of gypsum plaster is now 25kg rather than 40kg. The smaller bag is now helping to reduce manual handling strain – particularly when repetitive manual lifting is unavoidable.
We've already briefly discussed thermal laminates but I'd like to now give a little more information on them and also on how the designer needs to consider any potential risks which may be associated with their use.
As we've already said, thermal laminates combine the benefits of a plasterboard dry lining with backings of thermally efficient insulation materials. These backing materials include phenolic foam, extruded polystyrene, expanded polystyrene of high and low density, and mineral wool.
The laminates provide a dry internal lining with all the advantages of room located insulation. This is so important in intermittently heated rooms in order to reduce surface condensation and to provide comfort conditions for the occupants. Thermal laminates are mainly used for insulating walls in new buildings and to improve considerably the thermal insulation of existing masonry external walls. Thermal laminations can also be used to insulate at the rafter level of pitched roofs; and to contribute to the thermal insulation of new and existing timber flat roofs in conjunction with mineral wool insulation. However, the designer needs to consider any potential risks which may be associated with the backing materials of some of the laminates.
One potential risk is that related to the insulating plastic backings (of expanded polystyrene and extruded polystyrene) which, although they incorporate a flame retardant additive, they are combustible if exposed to a sustained source of ignition and will generate dense smoke. The flammability hazard increases when it is in dust form. Precautions may need to be included, therefore, in the health and safety plan and the health and safety file if, for example, blow torches or other forms of naked flame are used during construction or eventual maintenance.
Dust from phenolic foam is classified as a weak explosive. Therefore, suitable dust extraction and collection systems should be used to avoid possible explosions when phenolic foam backed laminates are cut using mechanical saws.
Suitable fire extinguishing media such as CO2, water, or foam should also be available on site. Electrical cables give off heat when in use. Where cables are covered by thermal insulation they may overheat and increase the risk of short circuit or fire. Cables should be fixed, therefore, so they can dissipate heat. This is one of the advantages of using metal framed wall lining systems which provide a cavity between the lining and the masonry background.
Where cables are covered by thermal insulation, advice needs to be obtained on what specific precautions are necessary. For example, by reference to the IEE Wiring Regulations or the Electricians Handbook. PVC sheathing to cables can have a reduced life expectancy if in direct contact with expanded or extruded polystyrene insulants. Fix PVC sheathed cables so that they are not in direct contact with the polystyrene backings of thermal laminates. Alternatively, run them in conduit.
Irrespective of what type of insulation is on the back of the thermal laminate, a suitable earthed metallic covering should be specified if the cable is within 50mm of the surface of the plasterboard lining. Alternatively, mechanical protection should be provided to avoid penetration by nails and screws, etc.
The backing material of thermal laminates should never be cut to accommodate services.
That concludes this talk on how designers can help to avoid or reduce health and safety risks in construction – particularly when specifying gypsum products and related systems.
Obviously a discussion of all of the risks is not possible but, on behalf of the GPDA, I have drawn to your attention some of the main health and safety risks which may arise during construction and eventual maintenance.
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