CARPENTRY - HOUSING
LIMITED HEIGHT SCAFFOLD This text introduces a variety of subject matter related to Building and Construction, at a basic level. It should be read in conjunction with “Basic Building and Construction Skills” , produced by TAFE and Addison, Wesley, Longman Australia Pty Limited, as between them they address the following:
Basic scaffolding, for use on a residential site, to a maximum height of 4 metres is outlined to provide learners with the basic skills and knowledge to safely erect: • unit frame; • modular; and • lightweight mobile types. Basic use of tube and coupler fittings will also be covered in relation to use as bracing, ties, barricades and/or shoring. Safe use of ladders, trestles and accessories is covered in relation to limited height scaffolding. This detail will provide learners with the basic skills and knowledge required to enter a Basic Scaffolders Certificate course. Main references include: • AS 6001 - 1999 Working Platforms for Housing Construction, and • AS/NZS 1576.1 - 1995 Scaffolding - General Requirements. A comprehensive ‘Glossary of Terms’ is included at the end of the text, which provides a detailed description of trade terms, technical content and some trade jargon.
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SCAFFOLDING DEFINITION • Scaffolding - is defined as a temporary structure, a temporary or permanent working or access platform (s), used for the purpose of conducting work activities. • Scaffolder - is a person engaged in the erection and dismantling of scaffolding. The Occupational Health & Safety Act of Australia requires that any person who acts as a scaffolder must have been properly trained in the erection and dismantling processes of the type of scaffolding being used. It is also important that building industry workers, especially scaffolders and riggers, are able to work safely at heights. Some people have a great fear of heights, regardless of the safety equipment used, which is known as vertigo. Physical fitness, a sober condition and general good health are important requirements for a person suited to this kind of work. In the past serious accidents have occurred due to one or more of these requirements not being met. The authority charged with the responsibility of overseeing and enforcing regulations and safety requirements is the WorkCover Authority of NSW. WHAT (WHO) IS WORKCOVER? WorkCover is an organization of people whose prime responsibility is to promote the health, safety and welfare of people at work through the administration of: • • • •
The Occupational Health & Safety Act 2000 and Regulation 2001; The Workers Compensation Act 1987; The Workplace Injury Management & Workers Compensation Act 1998; and Any associated legislation with the above.
WorkCover Inspectors Inspectors have similar powers to that of the NSW Police Service with infringement notices having the same format, apart from the authorities name. Their prime function is to: • • • • •
provide advice and information on workplace health and safety issues; investigate accidents and/or breeches of legislation; respond to complaints in relation to health and safety matters; resolve workplace health and safety disputes; and audit health and safety systems.
When workplaces fail to comply with WorkCover advice, and/or legislation, or where people are exposed to unnecessary risk(s), a WorkCover Inspector can:• • • •
issue notices requiring employers to remedy unsafe or hazardous conditions within a specific time frame, known as a ‘PINS ‘ notice; issue notices which prohibit work from continuing until conditions are safe; issue on the spot fines for non-compliance; collect written and visual evidence of breaches and recommend prosecution for serious breaches of the legislation; and also
The Inspector may visit any workplace at any time to check on the following: • noise pollution; • confined spaces safety; 2
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provision of safety for all people (including the general public) and property (equipment etc.) ; rejection of the use of defective equipment and plant. (scaffolding is classed as plant.); to ensure correct method and use of equipment is adopted in the workplace. (including the correct erection and dismantling procedures for scaffolding.)
Further information may be obtained by referring to the brochure available from WorkCover, i.e. ‘The role of a WorkCover Inspector’. Also, reference should be made to AS/NZS 4576 - 1995 and other relevant publications, brochures or booklets published by WorkCover. These WorkCover publications set out general rules and recommended work practices, which are known as ‘Codes of Practice’. WorkCover Authority Requirements • If the Scaffold is at a height from which a person or object could fall or be blown more than 4 metres, the person responsible for erecting the scaffolding must be the holder of a WorkCover ‘National Certificate of Competency’. People in training for this qualification may erect and dismantle scaffolding to allow them to gain experience, provided they are under the direct supervision of a qualified person. • Evidence of training must be recorded in a trainee ‘log Book’, which is kept by the trainee, and must be filled in at the end of each training session with the endorsement of the Supervisor. Note: Equipment suppliers share the responsibility with Principal employers, Engineers, Contractors and Supervisors to ensure correct training procedures and information is made available. Certification There are 3 WorkCover qualifications based on the ‘National Certification’ system. Each qualification requires the trainee to be at least 18 years old and pass competency assessments. Certificate classes are as follows: 1. Basic Scaffolding; 2. Intermediate Scaffolding; and 3. Advanced Scaffolding. Refer to AS/NZS 4576:1995 - Section 2 for further information relating to each qualification. GOLDEN RULES FOR THE WORKPLACE 1.
It is the responsibility of all workers to ensure every possible measure is taken to allow themselves, fellow workers and any workplace visitors to return to their homes at the end of the day in the same safe condition as they arrived.
2.
It is the responsibility of all authorised persons in or near the workplace to adhere to the workplace rules to ensure the safety of all others in that workplace.
3.
It is essential that no unauthorised persons enter the workplace undetected or unsupervised as they may unwittingly put themselves or other persons at risk of injury. This may be achieved by fencing off areas, barricading , erecting warning signs and/or posting traffic control personnel at entrances. © TAFE NSW Construction & Transport Division
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SAFETY RULES for the PLACEMENT and use of SCAFFOLDING A scaffold must be: 1. 2. 3. 4. 5. 6.
SAFE by design, type and construction. SAFE for access purposes. SAFE so that no persons or objects can fall or blow from it. SAFE so that any person can pass under or near it without being injured. SAFE from damage by vehicles, vessels, cranes or hoists. SAFE in it’s position from electrical wires, gases, explosives, chemicals, heat, nearby buildings or structures and is safe from collapse.
Note: Permits to erect scaffolding and hoardings may have to be obtained from Councils, R.T.A. and the Police Service if using roadways and public places to load, unload and set up scaffolding. Commonly used materials Scaffolding main structure: • Aluminium Tube 48 mm diameter wall thickness 4.5 mm • Steel Tube 48 mm diameter wall thickness 4 mm (Refer AS1576.3, AS1163 & AS1866.) • Timber should be of adequate size and strength rating to Engineers details. SITE HAZARD ASSESSMENT Sites should be assessed for hazards prior to the erection of scaffolding and should be continuously monitored to ensure that safe conditions are maintained. Initial assessment should look for the following: • possibility of scaffolders falling or dropping equipment; • proximity of power lines to the proposed location of the scaffold; • proximity of railway tracks to the proposed location of the scaffold; • proximity of gas mains, chemical dangers, explosive substances and the like to the proposed location of the scaffold; • setting up of the scaffold on or near open trenches or areas were trenches have been previous backfilled ; • areas likely to be excavated adjacent to the scaffold, whilst the scaffold is still in place; • soft and boggy ground surfaces; • surfaces that may be affected by heat, e.g. Asphalt may become soft; • surfaces that may be affected by vibration; • surfaces that may be affected by abnormally wet conditions; • bearing capacity of load bearing surfaces; • how level the supporting surface is to evenly distribute the load; • preservation orders on trees, surfaces, etc. in the vicinity of the scaffolds' construction; • demolition sites where the partial force of demolishing work may possibly be transposed to the scaffold; • anticipated dust and debris emission from the works performed on and near the scaffold. • the proximity to public places/traffic; • the loads to be imposed on the scaffolding during its use, including relative weather loads such as wind, snow, rain and ice, etc. on the ‘Shadecloth’ enclosure; 4
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• • • • • • •
obstruction of access ways and thoroughfares ; movement of vehicles, cranes, forklifts etc; corrosive substances in the area that may damage components and/or the health of workers; support needed to suspended surfaces prior to loading up and erection; working over brittle surfaces; interference with storage areas ; and incorporated access ways through the scaffold such as walk ways, ladders, etc,.
HAZARD ASSESSMENT MANAGEMENT After the hazards are assessed, a plan to control the risks has to be prepared and implemented to make the workplace safe. (Refer to AS/NZS 4576 - section 5 for further information.) Hazard Management should address the following: • eliminating or reducing the hazard; • warnings of potential hazards; • training personnel to control hazards • traffic and pedestrian control; and • use of appropriate safety equipment. Hazardous situations Climbing and Working at Heights. Where it is necessary to climb and/or work at heights, the Construction Safety Act basically states that where there is any possibility that anyone could fall more than 1.8 metres, precautions must be taken so that no one will be exposed to that danger. (When the Consolidated Regulations are gazetted in the future it is expected that this distance will be changed to 2 metres, which also encompass lift distances on scaffolding) All scaffolding at a height where a person or object could fall a distance of 2 metres or more must be fitted with approved handrails at 900 mm to 1000 mm above the deck, mid rails at 500 mm above the deck and toe boards of a height of at least 150 mm above the deck, which sit on the deck. These regulations are to be adopted as minimum requirements. Note: - Special purpose brick guards or other alternatives are also available. -Where the side of the scaffold is closer to a wall than the width of a scaffold plank guardrails may not be required on the wall side of the scaffold. Fig. 1 Protected scaffold work platform © TAFE NSW Construction & Transport Division
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Working close to openings Guardrails are required on all floors, ramps, platforms, landings, workplaces, stairs, stairways stairway landings where a person could fall a distance of 1.8 metres or more and around holes or excavations exceeding 1.5 metres in depth. Excavations will also need special shoring to guard against collapse of the sides, before work is carried out in the excavation.
Fig. 2 Guard rail for an open excavation.
Proximity to Power Lines The minimum distance to scaffolding is 4.6 metres. Where the minimum distance can not be maintained the following should occur: 1. Contact the appropriate electricity supply Authority. 2. High voltage mains (600v and over) should be de-energised and/or re-routed away from the work area prior to erection of the scaffold.. 3. Where de-energising of low and medium voltage mains is not practical, the electricity supply authority may decide to cover the mains with an approved coloured and stripped insulation material, commonly referred to as split rubber ‘tiger tails’ equal to the full length of the scaffold plus 5 metres either side. 4. Fence off the area using non-conductive material such as plywood sheeting where mains are within reach of the working platform.
Fig. 3 Safe scaffolding adjacent to power lines 6
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PERSONAL PROTECTIVE EQUIPMENT All personal protective equipment must comply with the relevant Australian Standards and be suitable for use on scaffolding. Safety helmets They must be worn at all times while scaffolding work is being carried out. They should be fitted with chin straps to prevent the helmet falling off, as scaffolding work requires the scaffolder to lean over to carry out the work. The date stamp on the helmet should be checked for currency as helmets should be replaced after two years if they have been exposed to ultraviolet light or at least tested for soundness as per AS 1801. Paints, felt-tipped markers and stickers should not be used as the solvents they contain will affect the strength of the helmet. Fig. 4 Safety helmet
Safety belts They should be fitted with frogs or tool holders to allow the scaffolder to carry the essential tools required for general scaffolding work. Safety footwear While working at ground level, the scaffolder must wear safety boots or shoes, which are usually fitted with steel caps. When working aloft the scaffolder should wear non-slip footwear which are flexible enough to allow the soles to grip on uneven surfaces. Eye protection Safety glasses or goggles should be worn when driving steel pins or wedges on the scaffold to protect the eyes from small pieces of metal, which may fly off and cause serious eye injury. Respirators Single or twin cartridge types fitted with appropriate dust or vapour filters should be worn when working on scaffolds where respiratory problems may occur, especially during demolition work. Ear protection Ear muffs or plugs should be worn to protect the ears from the constant high pitched noise of steel hitting steel during the erection process. Gloves Gloves similar to ‘Riggers gloves’ are suitable to protect the hands from abrasive, sharp, hot or extremely cold and icy conditions. © TAFE NSW Construction & Transport Division
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LADDER ACCESS Only single ladders of an acceptable material such as timber, Aluminium or fibreglass may be used for access to or inside a scaffold. When setting up ladders for use on scaffolds the following should be noted: • the pitch or slope of the ladder should be not less than one unit horizontally at the base to four units vertically in height (1 in 4) to the point of rest or attachment. It may be set at a maximum of one unit to six units, but one in four is preferable; • the top section of the ladder should extend at least one metre past the point of rest or attachment. This allows for safe access and exit from the ladder onto a landing or other surface; • landings or rest platforms should be not more than six metres apart to ensure ladder access is used; and • the clear width of an access platform should be not less than 675 mm, for persons and materials, and not less than 450 mm, for persons and hand tools only, when measured between guard rails.
Fig. 5 Typical ladder and acceptable angle
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Portable Ladder Safety (reference - WorkCover Publications) A ladder is used to gain access to areas above or below the ground, or other levels not provided with permanent access. It is important to realise that there are limits to the safe use of a ladder. Most accidents occur because these limits are exceeded. Portable ladders should comply with the requirements of the following relevant Australian Standard: • • • •
AS/NZS 1892.1 - 1996 Portable ladders Part 1: Metal; AS1892.2 - 1992 Portable ladders Part 2: Timber; AS/NZS 1892.3 - 1996 Portable ladders Part 3: Reinforced plastic; AS/NZS 1892.5 - 1999 Portable ladders Part 5: Selection, safe use and care.
Considerations for Safe Use 1.
All ladders should be adequately supported at the base. Wet grass, soft soil, makeshift supports or unstable soil should be avoided where possible. Use planks or boards under the feet to provide a solid base and if necessary tie the base to temporary pegs. All ladders should have rubber feet fitted.
2.
A ladder should never be ‘walked’ by the person standing on the ladder. This means the action of using the persons body movements to allow the ladder’s feet to move sideways or walk.
3.
Set the ladder at a slope of approximately 1 in 4. This means that the angle of the ladder against a support should be one metre out at the base for every 4 metres in height. This has been determined to be the most comfortable, safe angle for use.
4.
One ladder, one person with at least three limbs on the ladder at all times. There should only be one person on the ladder at any one time. That person should have either two feet and one hand or two hands and one foot on the ladder at all times.
5.
Never climb higher than the third rung from the top of the ladder. The ladder should be long enough to allow at least one metre of solid support beyond the height of the level of the task being undertaken.
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6.
Always use the correct length extension ladder. Extension ladders such as rope pulley types, are suitable for accessing high areas such as roof tops and tall trees. Use specialist pole ladders where the support surface is round. Ensure all latch hooks and ropes are fitted and functioning correctly. Long ladders or heavy ladders, i.e. more than 20 kg, should be handled by two persons.
7.
Safely use step ladders. Step ladders should only be used in the fully opened position on a stable, level surface. Lock-in side braces or spreaders should be used at all times.
8.
Safely use multipurpose ladders. Where used a s a single ladder, the length of the front edge of the stile including the feet shall not exceed 9.0m for industrial ladders and 5.0m for domestic ladders. Where used a s a step ladder, the length of the front edge of the stile including the feet to the centre of the hinge pivot-pin, shall not exceed 5.1m for industrial ladders and 2.4m for domestic ladders. Where used as a work platform. The slope of the front and rear stiles shall not be less than 65° and not greater than 80° above the horizontal.
9.
Always store ladders under cover when not in use. This prevents deterioration or damage. Timber ladders should never be painted, as defects and damage will not be easily detected.
10. Maximum length of ladders should be as follows: MATERIAL
SINGLE
EXTENSION
STEP
Metal and
9.0m (industrial)
15.0m (industrial) 6.1m (industrial)
5.0m
Reinforced plastic (fibreglass)
5.0 (domestic)
7.0 (domestic)
2.4 (domestic)
5.0m
Timber
9.2m (runged)
15.3m
5.5m (industrial)
5.1m
4.9m (cleated)
2.4m (domestic) 5.5m (platform)
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TRESTLE
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SPECIAL LADDERS, PLATFORMS AND ACCESSORIES Apart from the standard single, extension and step ladder types there are several specialist type ladders and platforms available for use in the Building industry. Trestle ladders These ladders should be capable of holding two scaffold planks and be self-supporting. Trestle ladders are widely used for painting ceilings, walls, windows, and wherever external or internal surfaces require construction and /or painting. They may be made from timber, aluminium or steel and be capable of supporting the load of two workers, when using two planks. Rungs are usually staggered on either side of the trestle in order to give a greater selection of working heights. Special features and requirements •
Trestles can be fitted with specially formed lipped trestle hinges which prevent over -opening and collapse. When trestles are fully opened the angle should not be greater than 36° or less than 24°. Spreader ropes or chains may also be used to control spread;
•
The maximum height of trestles is 4.8m;
•
They must not be spaced at more than 2.4m apart;
•
All work must be performed between the trestles without over-reaching;
•
Planks should overhang the trestle rungs by 250 mm, but not more than 300 mm;
•
When moving trestles and planks no person is to remain on the scaffold; and
•
Planks must be placed as horizontal working platforms only.
Fig. 6 Typical timber trestle © TAFE NSW Construction & Transport Division
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Aluminium maintenance platform Designed for safety, this mobile platform provides a large and comfortable working platform of 610 mm x 800 mm with 914 mm handrails on three sides. They are fitted with two 150 mm rubber wheels for easy moving. They range in sizes from 760 mm up to 3600 mm to the platform.
Fig. 7 Maintenance platform
Heavy duty aluminium step ladder They are used for very high jobs carried out internally, on a level floor or surface. They may be used to install light fittings or change globes and tubes, when painting ceilings, cleaning ceilings and upper sections of walls, etc. They have heavy duty side rails, reinforced treads, rubber feet and a safety hand rail. They range in size from 3600 mm up to 4800 mm.
Fig. 8 Heavy duty step ladder
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Multi-purpose ladder These ladders may be used for internal or external work and may be adjusted to form a variety of shapes to suit a variety of positions. They are easily carried and stored as they may be folded up to fit into the average car boot. They range in size from 1350 mm, when used as a step ladder, to 4800 mm when fully extended.
Fig. 9 Folding multi-purpose ladder
Pole chains and hoops These may be attached to the top end of single or extension ladders to allow a safe bearing position when the ladder is placed against a pole or column. The chain or hoop fits the contour of the vertical surface to prevent pivoting, which occurs when a rung rests against a round surface.
Fig. 10 Pole chain and pole hoop
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Ladder safety shoes These self-adjusting shoes allow a ladder to stand at any angle. The non-slip neoprene soles grip wet and slippery surfaces. These shoes can be fitted to any ladder.
Fig. 11 Safety ladder shoes
Ladder brackets They are made of mild steel and designed to take a single plank of up to 305 mm width. The bracket is adjusted using an adjustable steel linked chain, which is connected to the upper section of the bracket supported on the full width of the ladder rung. The single plank is designed to be used by only one person at a time to carry out light weight duties, such as a painter or cleaner.
Fig. 12 Adjustable ladder brackets
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SCAFFOLD PLANKS Timber, galvanised steel or boxed Aluminium are suitable materials for planks. Defective materials must not be used. Undersized members/components of a scaffold are deemed to be defective. Planks suitable for working platforms should be as follows: • Hardwood planks should have a minimum cross sectional size of 225 x 32 mm. • Oregon softwood planks should have a minimum cross sectional size of 225 x 38 mm. • Single ladder bracket planks should have a minimum cross sectional size of 300 x 38 mm. Note: These planks should only be used for light duty work, such as that carried out by a painter, and should not be used where a person or object could fall a distance of 2 metres or more. • System planks must have a minimum cross sectional size of 225 x 50 mm. Defects All planks should be checked for suitability prior to use and be regularly checked for possible defects such as splitting, cupping, twisting, wear or damage, knots, broken hoop iron straps on ends, end caps missing or welds broken on metal planks, projecting nails, saw cuts, mortar or concrete blobs on the face or edges, deep burns or any other visible defect. Platforms and Loads All platforms (or decks) must be at least 2 planks wide. Patented Modular system widths are available in 3 planks, 5 planks and 7 planks. Also hop up bracket accessories are available in 2 board and 3 board widths. All planks must be at least 220 mm in width. When assembling or dismantling scaffolding the scaffolder must work off a fully planked width deck, no more than one lift below the deck being set up or stripped. Access to decks must be via acceptable ladders or stairs onto a full width deck. Note: It is not permissible to climb the standards of a scaffold nor is it permissible to carry items up or down a ladder as both hands must be used on the ladder. Allowable load Capacities The allowable load capacities on scaffolding is determined largely by the spacing of the standards. To be able to exceed the following limits would require design approval from a Structural Engineer and WorkCover. TABLE 1 Based on AS/NZS 4576-1995 Duty classification as specified in AS/ NZS 1576.1
Approx. maximum total load for persons and materials in kilograms per platform per bay.
Approx. maximum mass of any single concentrated load of materials or equipment
Minimum length & width of platform in millimetres.
Light Duty Medium Duty Heavy Duty
225 450 675
100 150 200
450 900 1 000
Note: Materials must not be stored on light duty platforms that have the minimum allowable width. © TAFE NSW Construction & Transport Division
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Plank Platforms Building planks may be used for temporary work platforms and may be made from approved hardwood and softwood timber species, steel or box section aluminium in-line with the requirements of AS 1577 - 1993, Scaffold planks. The minimum width of a working platform is 450 mm, as required by AS 1576.1 - 1995, Scaffolding - general requirements, and is usually made up of two planks, each 225 mm wide, placed together on trestles or scaffolding. Toe board protection is not required for trestle platform work. Special features and requirements • • • • • • •
Planks must be free of knots, splits, decay and without twists or warps; Hardwood planks must be not less than 225 mm wide x 32 mm thick; Softwood planks must not be less than 225 mm wide x 38 mm thick; Planks must not be painted with opaque paints; To minimise damage to planks, the corners should be cut at an angle then bound with a metal strip to prevent the ends from splitting; Planks should not be dropped; and Planks should be stored in a dry, well ventilated area when not in use.
Galvanised hoop iron strap nail or screw fixed to both ends to prevent plank from splitting End bent into sides of plank Fig. 13 Treatment of timber plank ends
Prohibited ladders and defects Single stile ladders, extensions to the top of step ladders and ladders with rungs nailed to the front edge of the stiles are all prohibited from use, due to being classified as unsafe. Ladders with broken rungs, timber defects, broken or defective ropes, broken or loose tie rods, broken or missing feet or any metal defects such as bent rungs, cracked welds or bent stiles may not be used. Single stile
Extension
Standard step ladder
Rungs nailed to front of stile
Extension
Fig. 14 Prohibited ladders 16
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ROPES Ropes are used for a number of purposes in the building industry and there a number of different types available. Selecting the most appropriate rope for the job requires some background knowledge of the structure, characteristics, advantages and disadvantages of each type. The most common use for ropes will be lifting of scaffold planks, scaffold tube, small buckets of fittings and items or materials which are to be installed from the scaffold. A rope should be selected based on the following: • • •
the type of rope and its suitability for the task; the capacity of the rope; and no visible defects.
Rope Selection It is important to assess the maximum capacity of a rope to enable safe lifting. This assessment should be based on the following: 1. The angle of the lift - Unless qualified to calculate rope lifting on an angle, the scaffolder should always lift in a completely vertical direction to avoid placing undue stress on the rope. 2. The age and condition of the rope - Generally ropes used for lifting are classified into four groups according to their condition, as follows: • New rope. • Good used rope (Lifting capacity is reduced to 2/3rds new rope) • Sound old rope (Lifting capacity reduced to 1/2 that of good used rope.) • Not to be used. This is rope which has been identified as having defects and should be removed from the site. This may include some new ropes, which do not comply with standards or have visible defects. 4. The type of rope - Suitable rope should have long strands and be of a natural fibre such as Sisal or Manila. It should be constructed in the form of ‘Right hand hawser’ lay, which means that it consists of ‘fibres’ laid right hand to form ‘yarns’, which are laid left hand to form ‘strands’, which are laid right hand.
Fig. 15 Right hand lay hawser rope © TAFE NSW Construction & Transport Division
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Note: • Do not use short filament rope such as ‘Coir’ as it is not designed to take lifting loads. • Natural fibre rope should not be exposed to temperatures above 650 Centigrade, as this will render them defective. • Allow frozen rope to thaw before touching it as the strands become brittle when frozen and they may snap during handling. • It is advisable to check with manufacturers specifications if any doubt arises as to the use or the capacity of the rope. LIFTING WITH ROPES Safety Where possible all components must be received by lifting over the top of guardrails, with the exception of the first bay of each lift. To lift the first guardrail, either by hand or rope, the person lifting the component must lock him/herself around the standard with both arms and legs. This will allow the person to exert a leaning pressure on the standard without fear of falling while lifting the component. ATTACHING THE ROPE Ropes used for lifting must be properly secured to the object being lifted to prevent slipping or complete release. There are appropriate tying methods for particular objects as shown below: Clove Hitch This is used for starting a lashing and should always be used in conjunction with a half hitch.
Fig. 16 Clove hitch
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Round Turn and Two Half Hitches This is used to secure a rope under load, i.e. supporting a block and tackle to the scaffold.
Fig. 17 Round turn and two half hitches
Timber Hitch and Half Hitch Commonly used to secure a plank for lifting.
Fig. 18 Timber hitch and half hitch
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Rolling Hitch This is used to secure scaffold tube or round items for lifting. It should be used in conjunction with a half hitch to allow for control during lifting.
Fig. 19 Rolling hitch
Reef Knot and Sheet Bend These two knots are used to join the ends of ropes of the same or different sizes together.
Fig. 20 Reef knot and Sheet bend 20
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Snubber Turns This is used for holding or lowering a heavy load slowly. The rope is wound around a mid support with the load attached to the bottom end of the rope, while being lowered from the top.
Fig. 21 Snubber turns
Protecting the Ends of the Rope If the ends of rope are left ‘unrestrained’ after cutting to length, they will quickly begin to unravel. This constitutes a defect and may contribute to uneven loading of the strands of the rope during lifting. Ends of ropes need to be properly Whipped or Back-spliced , carried out by a person with the appropriate skills, to help give good service and to increase the safety in lifting and lowering.
Fig. 22 End protection for ropes © TAFE NSW Construction & Transport Division
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SCAFFOLD SYSTEMS Common Scaffolding Terms Bay - The space enclosed by four standards, two ledgers and two transoms. Lift - The vertical distance between ledgers where a working platform is created. The maximum lift is 2 metres although most unit frames have a lift of 1.8 m. Unit frame - A prefabricated structural scaffold frame placed vertically to transmit load to a supporting surface. Standard - A vertical member of a scaffold which transmits load to a supporting surface. Ledger - A horizontal scaffold member used to tie standards along the length. Transom - A horizontal scaffold member used to tie standards across the width. Putlog - A horizontal scaffold member placed transversely on top of ledgers to support planks. Plan brace - A diagonal bracing system in the horizontal plane along the length of the scaffold linking diagonally opposite standards. Face brace - A diagonal bracing system placed on the vertical face of the scaffold linking pairs of standards for the full height of the scaffold. Outrigger - An inclined bracing system placed at 90° on plan from the standards to the supporting surface. This system increases the base area of the scaffold thus allowing greater heights without the scaffold overturing. Working A surface created by planks at nominated lifts to allow the support of platform - persons and materials to carry out work safely. (min. 2 planks wide) Scaffold Types The common types available for use by persons working on residential sites, which may be constructed to a maximum working platform height of 4 metres are: • Unit Frame (Refer to AS 6001 - 1999 Working Platforms for Housing • Modular Construction, and AS/NZS 1576.1 1995 Scaffolding - General Requirements.) • Lightweight Mobile
UNIT FRAME There are many designs available, which have been approved by WorkCover NSW. Unit frame scaffolds consist of rigid prefabricated units. They are linked together, using the supplied accessories, to form a continuous scaffold with equally spaced work platforms. The units are of strong galvanised or zinc coated steel for protection against corrosion. They are easily handled by one person and can be stacked or neatly stored flat on top of one another. They are assembled in bays using diagonal cross braces, which are simply clipped top and bottom of the standards at each side, to hold them apart and square. Note: This system is no longer preferred by WorkCover and if used it must have handrails and toe boards fitted. 22
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Fig. 23 Typical unit frame
Accessories Unit frame scaffold comes with a number of accessories, which allows the units to be fitted together, multiplied in height and be set up for special use. They include the following: • • • • • • • •
galvanised planks; plank transoms; hop-up brackets; handrail standards; cross bracing; adjustable screw jacks (with base plates); separate base plates; and height couplers.
Fig. 24 Unit frame scaffolding parts © TAFE NSW Construction & Transport Division
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Risk Management/Assessment Before any scaffold is erected, a management plan should be adopted to identify any foreseeable hazards, assess the risks, eliminate and/or control the risks. This may achieved by developing a ‘Risk Management Plan’, consisting of a series of checks based on requirements of the OH&S Act, Regulation 2001, Codes of Practice and any other Hazard identification system available from WorkCover. Note: Once a plan has been developed it may be used every time a new project is undertaken with only minor modifications to the original. Risk Assessment Once a hazard has been identified, the risk must be assessed. This should include the following steps: Step 1
Identify factors that may be contributing to the risk (WorkCover Hazpak);
Step 2
Review the health and safety information developed by WorkCover, which is relevant to the particular hazard;
Step 3
Evaluate the likelihood of an injury occurring and the likely severity of an injury or illness that may occur;
Step 4
Identify the actions necessary to eliminate or control the risk; and
Step 5
Identify the records, which are necessary to keep to ensure that risks are eliminated or controlled.
This may be achieved by carrying out a ‘Hazard Profile’ related to the task and then forming a ‘Work Method Statement’. Some Considerations (WMS development) •
Unstable scaffold due to lack of competency in erection.
•
Overload of scaffold components.
•
Live electricity too close to area of scaffold erection and use.
•
Incorrect assembly of the first bay frames.
•
Climbing scaffold during erection .
•
Scaffold exceeds height to base dimension ratio.
•
Manual handling of scaffold components.
•
Movement of mobile scaffold tower.
•
Split or uneven decks/work platforms.
•
Unstable or incorrect dismantling of scaffold.
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ERECTION PROCEDURE FOR UNIT FRAME SCAFFOLD The total number of units and fittings are calculated and then placed in their approximate positions ready to be erected. Before commencing erection, prepare the supporting surface by making sure it is as level as possible, not going to subside under load, not block access and it complies with hazard assessment procedures. STEP 1
Select suitable sole plates, set out their position and bed them as level as possible, unless the surface is concrete or other firm surface.
Fig. 25 Preparation of sole plates on an uneven foundation
STEP 2 Stand a unit frame on each sole plate with a screw jack set to the lowest adjustment, fitted inside the base of each leg or standard. Attach the ends of a folding brace to one frame on one side and then attach the other end of the brace to the other unit frame on the same side.
Fig. 26 Stand frames and attach a folding brace
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STEP 3
Fit another folding brace to the other side of the same bay and then level up both ends using the adjustable screw jacks. A straight plank or a straight edge may be laid on top of the frames, over the length of the bay, to enable levelling of the bay. Repeat the process for the remainder of the bays required to make up the length of the scaffold. Note: It is critical that the first run of bays are level as this will ensure the whole scaffold remains level and plumb for its full height and length.
Fig. 27 Completing the required length of scaffolding
Fig. 28 Method of adjusting screw jacks 26
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STEP 4 Deck the working platform with planks for the full length of the scaffold to enable safe lifting and fitting of additional unit frames. To install an additional lift, insert the height couplers to connect the next unit frame and then repeat the previous 3 steps. When the desired height, Max. 4 metres, is reached the working platform should be fully decked out, toe boards fitted, hand rails fitted, additional bracing or outriggers fitted if required and the whole scaffold checked for completion.
Fig. 29 Completed unit frame scaffold
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MODULAR SCAFFOLD Similar in appearance to tube and fitting type scaffold, modular scaffold consists of separate members made up of steel pipe, (standards, ledgers, transoms and braces), which are held together with a patent wedging system, similar to 'Surelock', 'Cuplock', 'Kwikstage', etc.
Fig. 30 Typical modular components
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ERECTION PROCEDURE FOR MODULAR SCAFFOLD Before commencing erection, prepare the supporting surface by making sure it is as level as possible, not going to subside under load, not block access and complies with hazard assessment procedures. STEP 1
Select suitable sole plates, set out their position and bed them as level as possible, unless the surface is concrete or other firm surface.
Fig. 31 Prepare sole plates
STEP 2 Starting at one end of the proposed scaffold, place a pair of screw jacks set to their lowest adjustment on top of sole plates and slide the end of a standard over the top of each jack. Use a 2 metre standard on one side and a 3 metre on the other so that the joins in the standards will be staggered throughout the height, which will increase strength. Insert the transom and fit the wedges. Do not tighten the wedges at this stage.
Fig. 32 Place different height standards at one end © TAFE NSW Construction & Transport Division
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STEP 3 With one person holding the standards at one end, the other person fits a ledger to one side and then the other at the same height as the transom. Do not tighten the wedges at this stage.
Fig. 33 Fit first two ledgers
STEP 5 Attach the third and fourth standards to the ends of the ledgers and then fit a transom between them. Do not tighten the wedges at this stage.
Fig. 34 First bay set out 30
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STEP 5
Select the height for the first lift and insert another two transoms and ledgers to make a complete bay with two levels of connecting members. Note: The height of the ledgers should be set at the same level to distribute the loads evenly throughout the height of the scaffold. Now drive the wedges in firmly to make the frame rigid and level the first bay accurately.
Fig. 35 First lift completed and levelled
STEP 6
Repeat the same procedure to establish the total length of the scaffold and then add to the height of the first bay by inserting additional standards and locking them in with the patent vertical wedging system. Note: This system usually has prefabricated metal planks, which fit in between and rest on the transoms. Each subsequent lift should be decked out with planks to enable safe erection and lifting of members. When the desired height is reached, fit patent diagonal face bracing, which will be wedge fixed to the standards. Complete the scaffold by fitting toe boards, handrails, internal or external ladders and then check the whole scaffold for completion.
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Fig. 36 Completed work platform
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LIGHTWEIGHT MOBILE SCAFFOLD Lightweight mobile scaffold, similar to Instant Access, consists of light Aluminium tubing, which clips together, and is mounted on rubber castors for use on firm level surfaces. It is used for lightweight operations such as painting, changing lights, attaching fittings and fixtures, etc., inside structures where step ladders are too short or not safe for use.
SAFE WORKING LOAD - 2 persons + 25 kg materials = Total Load of 225 kg (Max. SWL 450 kg per tower, if 2 levels are used, i.e. 225 kg per level, where app). WIDTH 1.370m LENGTH -
1.8, 2.4, 3.0m
FRAME HEIGHTS BASE FRAME (with castors) -
2.0 to 2.2m
STANDARD EXT. FRAME -
1.6m (4 rungs)
GUARD RAIL FRAME -
1.1m
MAXI. PLATFORM HEIGHT -
4.0m free standing 9.0m with outriggers or truss base frame 5.8m free standing 10.8m with outriggers or truss base frame
MAX. WORKING HEIGHT -
Fig. 37 Typical components © TAFE NSW Construction & Transport Division
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ERECTION PROCEDURE FOR LIGHTWEIGHT MOBILE SCAFFOLD (Typical 1.8m (6') Square Tower described) Before commencing erection, ensure the supporting surface is as level as possible, not going to subside under load, not have any obstructions and complies with hazard assessment procedures. STEP 1
Attach horizontal brace (yellow hooks) to the vertical tube of base frame. Ensure castors are locked. At this point the frame is self supporting.
End base frame
Horizontal brace Clip hooked to inside of vertical member
Horizontal brace
End base frame Lockable caster
PLAN
ELEVATION
Fig. 38 Supporting first frame
STEP 2
Attach spare end of brace to the end of the other base frame. Attach the 2nd horizontal brace (yellow hooks) to the other side of the frame. Attach the plan brace(s) (black hooks) diagonally onto the vertical tube below the lowest base frame rung, or as low down as possible.
Attach braces to the 2nd end base frame Attach diagonal plan brace
Horizontal brace
Diagonal plan brace
PLAN
Connect 2nd horizontal brace
ELEVATION Fig. 39 First bay formed 34
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STEP 3 Attach four diagonal braces to the base of the unit as shown below. Level the unit using the adjustable legs.
Pair of diagonal braces
Attach Four diagonal braces
PLAN ELEVATION
Fig. 40 The first bay/base is complete
STEP 4
Additional extensions. Insert a frame, spigots first, into the top of the base unit and secure into the lock clips. Attach four diagonal braces to the frames as shown below.
Pair of diagonal braces
Diagonal braces End frame Connection between base frame and Extension frame
PLAN
ELEVATION Fig. 41 Fitting additional extensions
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STEP 5 Fit the plain platforms first, then the walk-through platform with the hinges on the trapdoor to the outside of the tower. Insert the guard rail spigots into the top of the last frame and secure the interlock clips. Attach the Horizontal Braces (yellow hooks) to the top rung of the guard rail frame and mid rails and one diagonal brace, for rigidity as shown below. Trap door
Walk through platform
Mid rails
Diagonal brace
Trap door Edge of platform open PLAN ELEVATION Fig. 42 Constructing the platform area
STEP 6 To complete the work platform, first fit the toe board to allow the trapdoor on the platform to open freely. Finally attach the ladder through the access platform and clip on the stand-off hooks, at the base of the ladder, to the corresponding rung on the frame. Ensure the access door movement is not impaired. Access ladder hooks onto top rails
Trap door open
Toe boards run around the perimeter of the platform
PLAN
ELEVATION
Fig. 43 Fitting of toe boards and trap door
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STEP 7 It may be necessary to fit ladder ‘change-over’ platforms, where towers require more than one ladder, to enable safe ladder change-over between platforms. Make sure four horizontal braces are also attached to act as guard rails and mid rails. Check leg adjustment and castor locks. Attach outriggers where required.
Fig. 44 Fitting accessories
Fig. 45 Completed square tower © TAFE NSW Construction & Transport Division
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OTHER FORMS OF LIGHTWEIGHT SCAFFOLD Truss Base Frame Wide base frames may be added to allow for greater heights to be obtained while retaining stability within the scaffold. Strong threaded leg adjustment is available so the scaffold may be kept plumb and level.
Fig. 46 Truss base frame added to a square tower
Fig. 47 Threaded leg adjustment 38
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Independent Scaffolding Used to create long platform runs for lightweight operations such as painting, sign writing, etc.
Fig. 48 Independent scaffold
Bridging Unit Allows access between tower scaffolds where access below must be maintained.
Fig. 49 Bridging unit connecting two towers © TAFE NSW Construction & Transport Division
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SLENDERNESS RATIO Where the height of a scaffold exceeds three times the minimum base dimension, the scaffold will require either tying to the structure or the fitting of outriggers/raker shores. Therefore, a scaffold with bay dimensions of 2.4 x 1.2 wide could be erected to a maximum height of 3.6 metres without tying or bracing to comply with the slenderness ratio. Ties to Structures Scaffolding may be tied to structures by the use of special couplers attached to steel tube, which is locked into both of the scaffolds vertical structural supports. The other end of the tube may be passed through an opening in the wall of the structure and tied to columns or reveals, by attaching short lengths of tube at right angles to form a hook or a complete frame around the structural support member. The height spacing of these ties should be a maximum of two lifts, i.e. 4 metres, and spaced horizontally at a maximum of three bays, i.e. approx. 7.2 metres, or up to approx. 14.4 metres where plan bracing has been added to the full length of the scaffold.
Column or pier
Short lengths of the tube locked around column
Blocks to protect column
Tube tied to vertical members
Opening in brick veneer wall
Tube tied to vertical members Unit frame scaffold
Unit frame scaffold brace
VERTICAL SECTION THROUGH WALL OPENING
PLAN OF ATTACHMENT TO A COLUMN
Fig. 50 Ties to structures
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Raker Shores These shores need to be set at 45° to the vertical structural members of the scaffold. If the raker shores are more than 2 metres in length they require horizontal tying back to the scaffold and along their length. They are placed at the same vertical height as the ties and at maximum 7.2 metres (3 bays) along the length of the scaffold.
Fig. 51 Raker shores
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GLOSSARY OF TERMS Back-splice - This is a treatment carried out on the end of ropes to prevent them from unlaying. The strands are woven back into the lay of the rope to secure them. Coir - This is the prepared fibre of the husk of the coconut used for making ropes, cordage, matting, etc. Coupler - This is an engineered structural connector used to join tubular scaffold members. Cupping - This is a timber defect, which causes the timber to curve across it’s width Hoop iron - This is a narrow strip of galvanised iron available in lengths or coils used mainly for tying. A typical use is where a timber roof beam is to be tied into the brickwork of a single skin garage. The hoop iron is built into the engaged pier, bent over the top of the beam and nail fixed into place to prevent the beam moving or lifting when the roof is under wind load. Knots - These are classified as timber defects when they are loose or decayed and occur where branch growth begins in a tree. They are very prominent in timbers such as Cypress pine and Slash pine. PINS - This is an acronym used by WorkCover NSW used to describe infringement notices they issue. It may be used for a ‘Provision of Improvement Notice’, which is issued when machinery etc. is found to be faulty or missing a guard. It may also mean a ‘Prohibition Infringement Notice’, which is issued when a structure, like a scaffold, is found to be faulty or dangerous. RTA - Roads and Traffic Authority of NSW Shadecloth - This is a woven polypropylene product available in rolls and is used on building sites to create silt fences and used as a safety enclosure on scaffolding to prevent materials and debris from falling from the scaffold. Shoring - A term used to describe the method of supporting the sides of a trench or wall. Slenderness ratio - This is the ratio of width or thickness to the height of a member, such as a column or post, or a structure like a building or a scaffold, which will have a bearing on its strength. Tiger tails - A plastic or rubber tape or tubing with a stripped and coloured surface, which is typically black and yellow. Vertigo - This is a condition which affects some people when they are elevated above ground level. The person may feel giddy, lose balance or even become unconscious. A person with this condition is usually referred to as being 'scared of heights'. Whipping - This is similar to a back-splice where the end of a rope is bound up with cord or twine to prevent it unlaying.
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FURTHER READING Barrington, J., D. Mylius & S. Arden, 1989, Book 1 Practical Australian Carpentry, Framing and Construction, McGraw Hill, Sydney Brown, B. and H. Slatyer, 1985, First published 1958, Second edition 1966, Third edition 1975, Fourth edition 1981, Fifth edition 1985, The Australian Carpenter and Joiner Volume 1, Standard Publishing Co Pty Ltd, Victoria. Matthews, John, 1993, Health and Safety at Work, Pluto Press, Leichhardt. National Committee on Rationalised Building, 1994, Fourth edition, Glossary of Building Terms, Standards Australia, Sydney. Standards Association of Australia, 1995, AS/NZS 4576: Guidelines for Scaffolding, Standards Australia, North Sydney. Standards Association of Australia, 1974, AS 1339-1974:Manual Handling of Materials, Standards Australia, North Sydney. Standards Association of Australia, 1977, AS 1895: Code of Practice for Guarding and Safe Use of Portable Electric Power Tools for Domestic Use, Standards Australia, North Sydney. Standards Association of Australia, 1989, AS 1627.2: Power Tool Cleaning, Standards Australia, North Sydney. Standards Association of Australia, 1983, AS 1319-1983: Safety Signs for the Occupational Environment, Standards Australia, North Sydney. Standards Association of Australia, 1991, AS 1576.1 - .3: Scaffolding, Standards Australia, North Sydney. Standards Association of Australia, 1993, AS 1577: Scaffold Planks, Standards Australia, North Sydney. Teachers of Building, First Edition - 1996 Reprinted 1997, 1998, 2nd Edition - 1999, Basic Building and Construction Skills, Addison Wesley Longman Australia Pty Ltd , South Melbourne. VIDEOS Construction and Transport Division, Ladders and Trestles (CTV04) available from Resource Distribution, Yagoona.
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