Construction work has undergone major changes. Once dependent upon craftsmanship with simple mechanical aids, the industry now relies largely on machines and equipment.
New equipment, machinery, materials and methods have contributed to the industry’s development. Around the middle of the 20th century, building cranes appeared, as did new materials like light-weight concrete. As time went on, the industry began using prefabricated construction units along with new techniques in the construction of buildings. Designers began to use computers. Thanks to such equipment as lifting devices, some of the work has become easier physically, but it has also become more complicated.
Instead of small, basic materials, such as bricks, tiles, board and light concrete, prefabricated construction units are commonly used today. Equipment has expanded from simple hand tools and transport facilities to complex machinery. Similarly, methods have changed, for instance, from wheelbarrowing to the pumping of concrete and from manual lifting of materials to the lifting of integrated elements with the assistance of cranes.
Innovations in equipment, machinery and materials can be expected to continue to appear.
European Community Directives Relating to Workers’ Health and Safety
In 1985, the European Community (EC) decided on a “New Approach to Technical Harmonization and Standards” in order to facilitate the free movement of goods. The New Approach directives are Community laws which set out essential requirements for health and safety that must be met before products may be supplied among member countries or imported to the Community. One example of a directive with a fixed level of demands is the Machine Directive (Council of the European Communities 1989). Products meeting the requirements of such a directive are marked and can be supplied anywhere in the EC. Similar systems exist for products covered by the Construction Products Directive (Council of the European Communities 1988).
Besides the directives with such a fixed level of demands, there are directives setting minimum criteria for workplace conditions. Community member states must meet these criteria or, if they exist, satisfy a more stringent safety level stipulated in their national regulations. Of specific relevance to construction work are the Directive on the Minimum Safety and Health Requirements for the Use of Work Equipment by Workers at Work (89/655/EEC) and the Directive on the Minimum Safety and Health Requirements at Temporary or Mobile Construction sites (92/57/EEC).
One of the types of construction equipment that frequently affects worker safety is scaffolding, the primary means of providing a work surface at elevations. Scaffolds are used in connection with construction, rebuilding, restoration, maintenance and servicing of buildings and other structures. Scaffold components may be used for other constructions such as support towers (which are not considered scaffolds) or for the erection of temporary structures such as grandstands (i.e., seating for spectators) and stages for concerts and other public presentations. Their use is associated with many occupational injuries, particularly those caused by falls from heights (see also the article “Lifts, escalators and hoists” in this chapter).
Types of scaffolds
Support scaffolds may be erected using vertical and horizontal tubing connected by loose couplers. Prefabricated scaffolds are assembled from parts manufactured in accord with standardized procedures that are permanently attached to fixation devices. There are several types: the traditional frame or modular type for building facades, mobile access towers (MATs), craftsmen scaffolds and suspended scaffolds.
Vertical adjustment of the scaffold
The working planes of a scaffold are normally stationary. Some scaffolds, however, have working planes that may be adjusted to different vertical positions; they may be suspended from wires that raise and lower them, or they may stand on the ground and be adjusted by hydraulic lifts or winches.
Erection of prefabricated facade scaffolds
The erection of prefabricated facade scaffolds should follow the following guidelines:
- Detailed erection instructions should be provided by the manufacturer and kept at the building site, and the work should be supervised by trained personnel. Precautions should be taken to protect anyone walking under the scaffold by blocking off the area, erecting additional scaffolding for the pedestrians to walk under or creating a protective overhang.
- The base of the scaffold should be placed on a firm, level surface. An adjustable steel base plate should be placed on planking or boards to create a sufficient surface area for weight distribution.
- A scaffold that is more than 2 to 3.5 m off the ground should be equipped with fall protection comprising a guard rail at a height of at least 1 m above the platform, an intermediate guard rail and a toe board. To move tools and supplies on or off the platform, the smallest possible opening in the guard rail may be created with a foot stop and guard rail on either side of it.
- Access to the scaffold should normally be provided by stairs and not ladders.
- The scaffold should be firmly secured to the wall of the building as directed by the manufacturer’s instructions.
- The stability of the scaffold should be reinforced using diagonal elements (braces) according to the manufacturer’s instructions.
- The scaffold should be as close as possible to the facade of the building; if more than 350 mm, a second guard rail on the inside of the platform may be needed.
- If planks are used for the platform, they must be secured to the scaffold structure. A forthcoming European standard stipulates that the deflection (bending) should be not more than 25 mm.
Earth-moving machinery is designed primarily to loosen, pick up, move, transport and distribute or grade rock or earth and is of great importance in construction, road-building and agricultural and industrial work (see figure 1). Properly used, these machines are versatile and can eliminate many of the risks associated with the manual handling of materials. This type of equipment is highly efficient and is used worldwide.
Figure 1. Mechanical excavation at a construction site in France
Earth-moving machines that are used in construction work and in road-building include tractor-dozers (bulldozers), loaders, backhoe loaders (figure 2), hydraulic excavators, dumpers, tractor-scrapers, graders, pipelayers, trenchers, landfill compactors and rope excavators.
Figure 2. Example of an articulated steer backhoe loader
The machine is versatile. It can be used for excavating, loading and lifting. The angling of the machine (articulation) enables it to be used in confined spaces.
Earth-moving machinery can endanger the operator and people working nearby. The following summary of the hazards associated with earth-moving machines is based on the European Community’s Standard EN 474-1 (European Committee for Standardization 1994). It points out the safety related factors to be considered when acquiring and using these machines.
The machine should provide safe access to the operator’s station and maintenance areas.
The minimum space available to the operator should allow for all manoeuvres necessary for the safe operation of the machinery without excessive fatigue. It should not be possible for the operator to have accidental contact with the wheels or tracks or the working equipment. The engine exhaust system should direct the exhaust gas away from the operator’s station.
A machine with an engine performance above 30 kW should be equipped with an operator’s cab, unless the machine is being operated where the year-round climate permits comfortable operation without a cab. Machines having an engine performance less than 30 kW should be fitted with a cab when intended for use where the air quality is poor. The airborne sound power level of excavators, dozers, loaders and backhoe loaders should be measured according to the international standard for measurement of airborne exterior noise emitted by earth-moving machinery (ISO 1985b).
The cab should protect the operator against foreseeable weather conditions. The interior of the cab should not present any sharp edges or acute angles that may injure the operator if he or she falls or is thrown against them. Pipes and hoses located inside the cab containing fluids that are dangerous because of their pressure or temperature should be reinforced and guarded. The cab should have an emergency exit separate from the usual doorway. The minimum height of the ceiling above the seat (i.e., seat-index point) depends on the size of the machine’s engine; for engines between 30 and 150 kW it should be 1,000 mm. All glass should be shatter-proof. The sound pressure level at the operator’s station should not exceed 85 dBA (ISO 1985c).
The design of the operator’s station should enable the operator to see the travelling and work areas of the machine, preferably without having to lean forward. Where the operator’s view is obscured, mirrors or remote cameras with a monitor visible to the operator should enable him or her to see the work area.
The front window and, if required, the rear window, should be fitted with motorized windscreen wipers and washers. Equipment for defogging and defrosting at least the front window of the cab should be provided.
Roll-over and falling object protection
Loaders, dozers, scrapers, graders, articulated steer dumpers and backhoe loaders with an engine performance of more than 15 kW should have a structure that will protect against roll-over. Machines intended for use where there is a risk of falling objects should be designed for and fitted with a structure that will protect the operator against falling material.
Machinery with provision for a seated operator should be fitted with an adjustable seat that keeps the operator in a stable position and allows him or her to control the machine under all expected operating conditions. Adjustments to accommodate to the operator’s size and weight should be easily made without the use of any tool.
The vibrations transmitted by the operator’s seat shall comply with the relevant international vibration standard (ISO 1982) for tractor-dozers, loaders and tractor-scrapers.
Controls and indicators
The main controls, indicators, hand levers, pedals, switches and so on should be selected, designed and arranged so that they are clearly defined, legibly labelled and within easy reach of the operator. Controls for machine components should be designed so that they cannot accidentally start or be moved, even if exposed to interference from radio or telecommunications equipment.
Pedals should have an appropriate size and shape, be surfaced with a non-skid tread to prevent slipping and be adequately spaced. To avoid confusion the machine should be designed to be operated like a motor vehicle, with pedals located in the same way (i.e., with the clutch on the left, the brake in the centre and the accelerator on the right).
Remote-controlled earth-moving machinery should be so designed that it stops automatically and remains immobile when controls are deactivated or the power supply to them is interrupted.
Earth-moving machinery should be equipped with:
- stop lights and direction indicators for machines designed with a permissible travelling speed over 30 km/h
- an audible warning device controlled from the operator’s station and of which the sound level should be at least 93 dBA at a 7 m distance from the front-end of the machine and
- a device which allows a flashing light to be fitted.
Creep (drift away) from the stopping position, for whatever reason (e.g., internal leakage) other than action of the controls, should be such that it does not create a hazard to bystanders.
Steering and braking systems
The steering system should be such that the movement of the steering control shall correspond to the intended direction of steering. The steering system of rubber-tyred machinery with a travelling speed of more than 20 km/h should comply with the international steering system standard (ISO 1992).
Machinery should be fitted with service, secondary and parking brake systems that are efficient under all foreseeable conditions of service, load, speed, ground conditions and slope. The operator should be able to slow down and stop the machine by means of the service brake. In case it fails, a secondary brake should be provided. A mechanical parking device should be provided to keep the stopped machine from moving, and it should be capable of remaining in the applied position. The braking system should comply with the international braking system standard (ISO 1985a).
To permit night work or work in dusty conditions, earth-moving machines should be fitted with large enough and bright enough lights to adequately illuminate both the travelling and the work areas.
Earth-moving machinery, including components and attachments, should be designed and constructed to remain stable under anticipated operating conditions.
Devices intended to increase the stability of earth-moving machinery in working mode, such as outriggers and oscillating axle locking, should be fitted with interlocking devices which keep them in position, even in case of hydraulic hose failure.
Guards and covers
Guards and covers should be designed to be securely held in place. When access is rarely required, the guards should be fixed and fitted so that they are detachable only with tools or keys. Whenever possible, guards should remain hinged to the machine when open. Covers and guards should be fitted with a support system (springs or gas cylinders) to secure them in the opened position up to a wind speed of 8 m/s.
Electrical components and conductors should be installed in such a way as to avoid abrasion of wires and other wear and tear as well as exposure to dust and environmental conditions which can cause them to deteriorate.
Storage batteries should be provided with handles and be firmly attached in proper position while being easily disconnected and removed. Or, an easily accessible switch placed between the battery and the earth should allow the isolation of the battery from the rest of the electrical installation.
Tanks for fuel and hydraulic fluid
Tanks for fuel and hydraulic and other fluids should have means for relieving any internal pressure in case of opening and repair. They should have easy access for filling and be provided with lockable filler caps.
The floor and interior of the operator’s station should be made of fire-resistant materials. Machines with an engine performance exceeding 30 kW should have a built-in fire extinguisher system or a location for installing a fire extinguisher that is easily reached by the operator.
Machines should be designed and built so that lubrication and maintenance operations can be conducted safely, whenever possible with the engine stopped. When maintenance can be performed only with equipment in a raised position, the equipment should be mechanically secured. Special precautions such as erecting a shield or, at least, warning signs, must be taken if maintenance must be performed when the engine is running.
Each machine should bear, legibly and indelibly, the following information: the name and address of the manufacturer, mandatory marks, designation of series and type, the serial number (if any), the engine power (in kW), the mass of the most usual configuration (in kg) and, if appropriate, the maximum drawbar pull and maximum vertical load.
Other markings that may be appropriate include: conditions for use, mark of conformity (CE) and reference to instructions for installation, use and maintenance. The CE mark means that the machine meets the requirements of European Community directives relevant to the machine.
When the movement of a machine creates hazards not obvious to a casual spectator, warning signs should be affixed to the machine to warn against approaching it while it is in operation.
Verification of safety requirements
It is necessary to verify that safety requirements have been incorporated in the design and manufacture of an earth-moving machine. This should be achieved through a combination of measurement, visual examination, tests (where a method is prescribed) and assessment of the contents of the documentation that is required to be maintained by the manufacturer. The manufacturer’s documentation would include evidence that bought-in components, such as windscreens, have been manufactured as required.
A handbook giving instructions for operation and maintenance should be supplied and kept with the machine. It should be written in at least one of the official languages of the country in which the machine is to be used. It should describe in simple, readily understood terms the health and safety hazards that may be encountered (e.g., noise and hand-arm or whole-body vibration) and specify when personal protective equipment (PPE) is needed. A space intended for the safekeeping of the handbook should be provided in the operator’s station.
A service manual giving adequate information to enable trained service personnel to erect, repair and dismantle machinery with minimum risk should also be provided.
In addition to the above requirements for design, the instruction handbook should specify conditions that limit use of the machine (e.g., the machine should not travel at a greater angle of inclination than is recommended by the manufacturer). If the operator discovers faults, damage or excessive wear that may present a safety hazard, the operator should immediately inform the employer and shut down the machine until the necessary repairs are completed.
The machine must not attempt to lift a load heavier than specified in the capacity chart in the operating manual. The operator should check how the slings are attached to the load and to the lifting hook and if he or she finds that the load is not attached safely or has any concerns about its safe handling, the lift should not be attempted.
When a machine is moved with a suspended load, the load should be kept as near to the ground as possible to minimize potential instability, and the travel speed should be adjusted to prevailing ground conditions. A rapid change of speed should be avoided and care should be taken so the load does not begin to swing.
When the machine is in operation, no one should enter the work area without warning the operator. When the work requires individuals to remain within a machine’s work area, they should observe great care and avoid unnecessarily moving or remaining under a raised or suspended load. When someone is within the work area of the machine, the operator should be particularly careful and operate the machine only when that person is in the operator’s view or his or her location has been signalled to the operator. Similarly, for rotating machines, such as cranes and backhoes, the swing radius behind the machine should be kept clear. If a truck must be positioned for loading in a way such that falling debris might hit the driver’s cab, no one should remain in it, unless it is strong enough to withstand impact of the falling materials.
At the beginning of the shift, the operator should check brakes, locking devices, clutches, steering and the hydraulic system in addition to making a functional test without a load. When checking the brakes, the operator should make certain that the machine can be slowed down rapidly, then stopped and safely held in position.
Before leaving the machine at the end of the shift, the operator should place all operating controls in the neutral position, turn off the power supply and take all necessary precautions to prevent unauthorized operation of the machine. The operator should consider potential weather conditions that might affect the supporting surface, perhaps causing the machine to be frozen fast, tipped over or sunk, and take appropriate measures to prevent such occurrences.
Replacement parts and components, such as hydraulic hoses, should be in compliance with the specifications in the operating manual. Before attempting any replacement or repair work in the hydraulic or compressed air systems, the pressure should be relieved. The instructions and precautions issued by the manufacturer should be observed when, for instance, a working attachment is installed. PPE, such as a helmet and safety glasses, should be worn when repair and maintenance work are done.
Positioning a machine for work
When positioning a machine, the hazards of overturning, sliding and subsidence of the ground beneath it should be considered. When these appear to be present appropriate blocking of adequate strength and surface area should be provided to assure stability.
Overhead power lines
When operating a machine near overhead power lines, precautions against contact with the energized lines should be taken. In this connection, cooperation with the power distributor is advisable.
Underground pipes, cables and power lines
Prior to starting a project, the employer has the responsibility to determine if any underground power lines, cables or gas, water or sewer pipes are located within the work site and, if so, to determine and mark their precise location. Specific instructions for avoiding them must be given to the machine operator, for instance, through a “call before you dig” program.
Operation on roads with traffic
When a machine is operated on a road or other place open to public traffic, road signs, barriers and other safety arrangements appropriate for the traffic volume, vehicle speed and local road regulations should be used.
It is recommended that transport of a machine on a public highway should be executed by truck or trailer. The hazard of overturning should be considered when the machine is being loaded or unloaded, and it should be secured so that it will not shift while in transit.
Materials used in construction include asbestos, asphalt, brick and stone, cement, concrete, flooring, foil sealing agents, glass, glue, mineral wool and synthetic mineral fibres for insulation, paints and primers, plastic and rubber, steel and other metals, wallboard, gypsum and wood. Many of these are covered in other articles in this chapter or elsewhere in this Encyclopaedia.
The use of asbestos for new construction is prohibited in some countries but, almost inevitably, it will be encountered during the renovation or demolition of older buildings. Accordingly, stringent precautions are required to protect both the workers and the public against exposures to asbestos that was previously installed.
Bricks, concrete and stone
Bricks are made of fired clay and grouped into facing bricks and brick stones. They can be solid or designed with holes. Their physical properties depend on the clay used, any added materials, the method of manufacture and the incineration temperature. The higher the incineration temperature, the less absorbency the brick will exhibit.
Bricks, concrete and stone containing quartz can produce silica dust when cut, drilled or blasted. Unprotected exposures to crystalline silica can increase susceptibility to tuberculosis and cause silicosis, a disabling, chronic and potentially fatal lung disease.
Materials commonly used for interior flooring include stone, brick, floorboard, textile carpeting, linoleum and plastic. The installation of terrazzo, tile or wood flooring can expose a worker to dusts that can cause skin allergies or damage the nasal passages or lungs. In addition, the glues or adhesives used for installing tiles or carpeting often contain potentially toxic solvents.
Carpetlayers can damage their knees from kneeling and striking a “kicker” with the knee in stretching the carpeting to fit the space.
Glue is used to join materials through adhesion. Water-based glue contains a binding agent in water and hardens when water evaporates. Solvent glues harden when the solvent evaporates. Since the vapours can be harmful to health, they should not be used in very close or poorly ventilated areas. Glues consisting of components that harden when mixed can produce allergies.
Mineral wool and other insulation
The function of insulation in a building is to achieve thermal comfort and to reduce energy consumption. To achieve acceptable insulation, porous materials, such as mineral wool and synthetic mineral fibres, are used. Great care must be taken to avoid inhaling the fibres. Sharp fibres can even penetrate the skin and cause an annoying dermatitis.
Paints and primers
Paints are used to decorate the exterior and interior of the building, protect materials like steel and wood against corrosion or decay, make objects easier to clean and provide signals or road-markings.
Lead-based paints are now being avoided, but they may be encountered during the renovation or demolition of older structures, particularly those made of metal, such as bridges and viaducts. Inhaled or swallowed fumes or dusts can cause lead poisoning with kidney damage or permanent nervous system damage; they are particularly dangerous for children who may be exposed to lead dusts carried home on work clothes or shoes. Precautionary measures must be taken whenever lead-based paints are used or encountered.
Use of cadmium- and mercury-based paints is prohibited for use in most countries. Cadmium can cause kidney problems and some forms of cancer. Mercury can damage the nervous system.
Oil-based paints and primers contain solvents which may be potentially hazardous. To minimize solvent exposures, the use of water-based paints is recommended.
Plastic and rubber
Plastic and rubber, known as polymers, can be grouped into thermoplastic or thermosetting plastic and rubber. These materials are used in construction for tightening, insulation, coating, and for products like piping and fittings. Foil made of plastic or rubber is used for tightening and moisture-proof lining and may cause reactions in workers sensitized to these materials.
Steel, aluminium and copper
Steel is used in construction work as a supporting structure, in reinforcement rods, mechanical components and facing material. Steel may be carbon or alloy; stainless steel is a type of alloy. Important steel properties are its strength and toughness. Fracture toughness is important in order to avoid brittle fractures.
The properties of steel depends on its chemical composition and structure. Steel is heat-treated in order to release internal strain and to improve weldability, strength and fracture toughness.
Concrete can withstand considerable pressure, but reinforcement bars and nets are required for acceptable tensile strength. These bars typically have a considerable carbon content (0.40%).
Carbon steel or “mild” steel contains manganese, which, when released in fumes during welding, can cause a Parkinson’s disease-like syndrome, which can be a crippling nervous disorder. Aluminium and copper can also, under certain conditions, be harmful to health.
Stainless steels contain chromium, which increases corrosion resistance, and other alloy elements, such as nickel and molybdenum. But welding of stainless steel can expose workers to chromium and nickel fumes. Some forms of nickel can cause asthma or cancer; some forms of chromium can cause cancer and sinus problems and “nose holes” (erosion of the nasal septum).
Next to steel, aluminium is the most commonly used metal in construction, because the metal and its alloys are light, strong and corrosion-resistant.
Copper is one of the most important metals in engineering, because of its corrosion-resistance and high conductivity for electricity and heat. It is used in energized lines, as roof and wall coating and for piping. When used as a roof coating, copper salts in the rain runoff can be harmful to the immediate environment.
Wallboard and gypsum
Wallboard, often coated with asphalt or plastic, is used as a protective layer against water and wind and to prevent seepage of moisture through the building elements. Gypsum is crystallized calcium sulphate. Gypsum board consists of a sandwich of gypsum between two layers of cardboard; it is widely used as wall covering, and is fire-resistant.
Dust produced when cutting wallboard can lead to skin allergies or lung damage; carrying oversize or heavy board in awkward postures can cause musculoskeletal problems.
Wood is widely used for construction. It is important to use seasoned timber for construction work. For beams and roof trusses of considerable span, glue-laminated wood units are used. Measures are advisable to control wood dust, which, depending on the species, can cause a variety of ailments including cancer. Under certain conditions, wood dust can also be explosive.