GUIDELINES
FOR ACCESS SCAFFOLDING
scaffoldsafetyimages/fig
OSH Engineering Unit
July 1997
An access scaffold is a temporary structure usually made of metal frames and tubing, which provides temporary support and access for workers and materials used in construction, demolition, repair and maintenance work. Scaffolding, when not constructed and used properly, can result in serious injury, and sometimes death. In Manitoba, over 7,000 work days are lost annually as a result of scaffold-related accidents.
This guideline is intended to provide information for employers and workers on the safe erection, use and maintenance of access scaffolding in the workplace. It is intended to provide practical information related to the requirements of the regulations pertaining to scaffolding. For specific regulatory requirements regarding scaffolds, please consult the regulations adopted under the Workplace Safety and Health Act.
Some of the information and illustrations in this guideline are based on information provided courtesy of the Construction Safety Association of Ontario (CSAO)
T A B L E
O F C O N T E N T SA. RESPONSIBILITIES/DESIGN APPROVALS
B. SCAFFOLD TYPES AND SELECTION
C. SCAFFOLD FOUNDATION AND SUPPORT
D. SCAFFOLD ERECTION AND BRACING
GLOSSARY OF TERMS
TABLE 1 - APPROX. WEIGHTS OF BUILDING MATERIALS
A. Responsibilties/Design Approvals
Employers
It is the employer’s responsibility to ensure that proper scaffolding material and equipment is provided at the project site. In addition, all workers must be trained in proper scaffold use, erection, and maintenance. The workers shall be instructed on the safe working load that the scaffold is intended to carry. The employer is required to provide all necessary personal protective equipment,(i.e. safety headwear, footwear, fall protection systems, etc.) to workers erecting and using the scaffold.
If scaffolds are designed by a professional engineer, the employer must ensure that they are constructed in accordance with the design.
The employer must appoint a skilled and experienced worker to supervise the erection, use and dismantling of the scaffold system. This is to ensure that the correct procedures are followed, especially if specialized design and engineered drawings are required.
Principal Contractors have the overall responsibility on a project to ensure that scaffolding is erected and maintained in accordance with regulatory requirements and good practice.
Workers
Workers must ensure that they follow safe work procedures and use all necessary equipment and any necessary personal protective devices when erecting and using scaffold systems. Workers must also take care to protect other workers when working on scaffolding.
All workers must be equipped with and use safety footwear and headwear when erecting and working on a scaffold system. When practicable, proper fall protection systems should be incorporated into the erection and dismantling of scaffold systems.
Supervision
Scaffolds must always be erected under the supervision of a worker experienced in their construction and use. Although scaffold systems vary between manufacturers, certain fundamental requirements are common to all scaffold systems. The supervisor is able to be on-site and confirm that the scaffold is erected in accordance with the manufacturer’s recommendations and/or engineer’s design.
Design Approvals
All open access scaffolding in excess of 15 metres (50 ft) in height must be designed by a professional engineer, and erected, used and maintained in accordance with the engineered design. If the scaffolding is to be enclosed or hoarded, then an engineer must be consulted for the design and erection of all hoarded scaffolding greater than 7.5m (25 ft.) in height.
Engineer designed scaffold drawings and specifications shall include complete information on such details as tie-back specifications, design load and wind loading criteria, foundation details, and design criteria for wind load on enclosed or hoarded scaffolds. The design must include all design details related to the application of the scaffolding system. For example, if the scaffold is to be tied-back to the structure, it must be clear whether the design includes provision for the hoarding of the scaffold.
The employer shall ensure that the engineered scaffold system is inspected, by a professional engineer, after its erection and prior to worker use. This is to ensure that the scaffold has been erected in accordance with the design specifications. A copy of the design drawings must be kept at the project site and a written record of the engineer’s inspection provided to the employer.
Inspections
The employer shall ensure that all scaffolding systems are inspected prior to workers utilizing the system and when work from the scaffolding is suspended for periods of two (2) days or more, or during periods of severe weather conditions, the scaffold system shall be inspected on a regular schedule and a record of the inspections maintained at the job site.
CSA Standard
The applicable reference standard for access scaffolding is CSA S269.2-M87 "Access Scaffolding for Construction Purposes". This standard provides detailed criteria for the design of access scaffolding, including loads and forces, structural analysis and design, erection, dismantling, safety requirements, maintenance and test procedures.
Manitoba regulations pertaining to access scaffolding take precedence over any provision in the CSA standard that may differ from regulatory requirements.
STANDARD FRAME SCAFFOLD
B. SCAFFOLD TYPE AND SELECTION
Selecting a Scaffolding System
The safe and efficient use of scaffolding depends, first of all, on choosing the right system for the job. If the scaffold’s basic characteristics are unsuited to the task, or if all the necessary components are not available, proper erection and use is compromised.
Selection of scaffolding and related components requires an understanding of site conditions and the work to be undertaken. The employer must consider the following:
Basic Considerations:
-the weight of workers, tools, materials and equipment to be carried by the scaffold system (safe work load)
-site conditions (interior, exterior, backfill, concrete floors, type and condition of walls, access for the equipment, variations in elevation, anchorage points, etc)
-height to which the scaffold may be erected (overhead power lines, tie-backs)
-type of work that will be done from the scaffold (masonry work, sandblasting, painting, metal siding, mechanical installation, suspended ceiling installation)
-duration of work
-weather conditions, including wind and ice build-up
-requirements for pedestrian traffic through and under the scaffold area
-means of access to the scaffold
-configuration of the building or structure being worked on
-special erection or dismantling circumstances.
-hoarding
|
BASIC TYPES OF SCAFFOLDS |
Standard Tubular Frame Scaffold
This is the most frequently used scaffolding system in construction in Manitoba. It is made of steel tubing or aluminum and is manufactured in various configurations and spans.
The advantage of this type of scaffold is its portability and relative ease of assembly. Its main disadvantage is the fact that, because it is made up of component parts, all the parts may not be at the site or someone decides that they are not all required.
It is essential with steel frame scaffolds that all components and parts are installed properly, especially all connections and bracing components, base plates, work platforms and tie-backs.
The spans in frame scaffolds normally range from 1.5 metres (5 ft) to 3 metres (10 ft) These span lengths are varied using different lengths of bracing. Most manufacturers have braces which will provide spans between 1.5 metres (5 ft) and 3 metres (10 ft) in length. However, some manufacturers have special braces both shorter and longer than this range.
Walk -Through (Masonry) Frame Scaffold
The standard walk-through frame scaffold is a variation of the standard tubular frame type. It is designed to accommodate pedestrian traffic at the ground or street level and is frequently used by the masonry trade to provide greater height per tier and easier movement and distribution of materials on platforms.
There is a tendency to overload this type of scaffold, or not provide the proper width or amount of work platform support. Consideration must also be given to pedestrian safety. All employers shall ensure pedestrians are protected from falling debris and materials.
Rolling Scaffolds
Scaffolds which need to be moved frequently are often equipped with castors or wheels. The most important consideration with these scaffolds is that both horizontal and vertical bracing must be used with the standard tubular frame systems. Also, outrigger supports may have to be provided to ensure the stability of the scaffold.
Rolling scaffolds must be erected so that the height-to-base width ratio is no greater than 3 to 1. This limits platform height with standard outrigger stabilizers and single span towers to approximately 9.5 metres (30 ft), [this assumes outrigger stabilizers are 3 metres (10 ft across)].
Castors on rolling scaffolds must be equipped with braking devices. The type of castor used should not only include a braking device but must also be selected based upon the loads under which it will be operating. Additionally, the ground surface upon which the castor will be used must be free of defects such as potholes and other obstructive debris, which may cause the scaffold to topple when it is being moved.
NOTE: No worker may "ride" the scaffold when it is being moved from one location to the other, unless the worker is secured to the building in a manner to prevent the worker from falling, if the scaffold overturned or became unstable.
F arm Wagon Type
Scaffolds erected on farm wagons or other devices with pneumatic tires are frequently used for exterior building applications where movement of the scaffold is necessary. For safe, effective use, the area around the building should be well compacted, relatively smooth and level. The farm wagon type scaffold is subject to the 3 to 1 height-to-width ratio, and is rarely practical for platform heights greater than 8.5 metres (28 ft).
This type of scaffold should be equipped with outrigger beams with levelling devices. If such stabilizers can not be used, a means must be provided to ensure the stability of the scaffold should any tire deflate or lose pressure. ( i.e. suitable structural blocking under the wagon axles)
Fold-Up Scaffold Frames
Fold-up scaffold frames are frequently used by trades such as electricians, painters and suspended ceiling workers. Widths range from 330 mm (13 ") to the standard width of about 1.5 metres (5 ft). Frequently made of aluminum, this type of scaffold is easily and quickly transported, erected and moved about construction sites and from job to job. It should be used only on a smooth, hard surface and equipped with a fully decked work platform, and castors equipped with brakes.
Adjustable Scaffolds (Baker Scaffold)
Adjustable platform height scaffolds are a different variation on the fold-up scaffolds. Adjustable scaffolds are lightweight and easily adjusted for height considerations. It also has a minimum number of components, which makes it easily transportable from job to job.
These devices should ONLY be used on smooth, hard surfaces and are not intended to carry heavy loads.
Tube-And-Clamp (Coupler) Scaffolds
This scaffolding system consists of individual aluminum or steel tubes or pipes, serving as posts, braces, ties, etc., which are joined together in the field by means of special clamps or couplers, to form an integral load-carrying structure for the support of workers, equipment and materials.
Tube-and-Clamp scaffolds are frequently used where obstructions or non-rectangular structures are encountered. The scaffolds are infinitely adjustable in height and width. They can also be used for irregular and circular vertical configurations.
Workers erecting tube-and-clamp scaffolds must be trained and experienced. For each set-up, a sketch or drawing should be prepared by an experienced person skilled in this type of system. The requirement for engineer’s approvals also apply to tube and clamp access scaffolding.
C. SCAFFOLD FOUNDATION AND SUPPORT
Scaffolds must be erected on surfaces which can adequately support all loads applied by the scaffold. To support scaffolds, backfilled soils must be well compacted and levelled. Mud and soft soil should be replaced with compacted gravel or crushed stone. Embankments that appear unstable or susceptible to erosion must be contained.
Where mudsills must be placed on sloping ground, levelling the area should be done by excavating, rather than backfilling. Backfilled material, unless properly compacted and levelled, does not have the same capacity to support a load as undisturbed soil.
For sloped surfaces, it may be necessary to use half-frames to accommodate the grade change. For these situations the bracing is usually provided by using tube-and-clamp components.
Scaffolds erected on any type of soil or gravel, etc. must be supported on a mudsill . The mudsill must be a minimum of 50 mm x 250 mm (2" x 10") S-P-F plank and must be continuous under at least two consecutive end-frames or supports. For frame scaffolds, there must be proper base plates with adjustable screw jacks under each post support, when the frames are supported on a smooth concrete surface. A proper base plate is required under all circumstances. The base plate should rest centrally on the mudsill and the sill should project at least 600 mm (2 ft) beyond the scaffold foot ends or where individual sills butt together. Mudsills should be placed along the length of the frames, in preference to the width, for better overall support.
The use of blocking or packing such as bricks, short pieces of lumber or scrap material either under scaffold base plates or under mudsills is prohibited . Vibration can cause blocking to move or shift, and leave a scaffold leg unsupported. Under such conditions, the scaffold can topple when heavy loads are applied.
Take particular care when erecting scaffolds on frozen ground. Thawing soil is often water-soaked, resulting in considerable loss of soil bearing capacity. Thawing is an important consideration where tarps or other covers will be placed around a scaffold and the enclosed area is to be heated.
D. SCAFFOLD ERECTION AND BRACING
Fittings and Accessories
It is absolutely essential to install all the parts, fittings and accessories required for a scaffold, so that it is erected in accordance with manufacturers’ instructions. If parts are not available at the site, make sure that they are obtained as soon as possible. Do not attempt to erect a scaffold with only a partial supply of base plates, braces, connectors, etc. Ensure that all the components are in good condition and examine them to see that they are not damaged. All fittings must be positive and securely connected.
Base Plates and Screw Jacks
Base plates must be used on all non-mobile scaffolding of a size and capacity as specified by the manufacturer. Combination base plates with screwjacks must not be over-extended. A good rule of thumb is to use the 2:1 ratio, the outside (visible) length of exposed screw can only be a maximum of twice the inside screw length. (For example, a 24 inch long screw jack can only have 16 inches of exposed screw and 8 inches of inside length. Consult the manufacturer for complete design information on the particular screw jack.)
Plumbness
It is absolutely essential that the scaffold is erected plumb, to ensure maximum structural capability of the system. When the first tier of scaffold is erected, check for plumbness and continue doing so as the scaffold is built. Where necessary, adjustments can be made by using the adjustable screw jacks on the base plates. Settlement or slight variations in the fit of the components may require additional adjustments as tiers are added to the scaffold tower. The scaffold frame should be checked for plumbness after each tier is added to the scaffold. CSA Standard S269.2-M87 specifies the following criteria for plumbness:
| Maximum Variation from Plumb | Maximum Height of Scaffold |
| 1/2 "( 12mm ) | 10 ' ( 3m ) |
| 3/4 " ( 19mm ) | 20 ' ( 6m ) |
| 1 1/2 " ( 38mm ) | Maximum Height |
In addition to the scaffold being plumb, each working deck must be level.
Bracing
Bracing helps keep the scaffold frame plumb and square in both vertical and horizontal planes. Once frames have been fitted with adjustable base plates, the braces must then be attached for each tower span. The braces should slide into place easily. If force is required, either the braces are bent or damaged or the frames are out of plumb or square. Braces should be secured at each end and the self-locking devices are moving freely and have fallen into place. Rust or slight damage can prevent some of these devices from working properly, so it is essential to maintain the components in proper working condition.
Bracing in the vertical plane is a must on both sides of every frame. Bracing in the horizontal plane should be provided at the joint of every third tier of frames. Horizontal bracing should coincide with the point at which scaffold is tied to the building or structure being worked on. Although it is sometimes omitted, horizontal bracing is necessary to maintain scaffold stability and full load-carrying capacity. The use of horizontal bracing on the first tier helps to square up the scaffold before nailing base plates to mudsills.
Bracing must be adequately secured in place. Otherwise, scaffold movement can dislodge the brace, reducing the stability of the scaffold. These devices must operate freely for ease of erection and dismantling. Trying to release a jammed or rusted drop hook when dismantling a scaffold has resulted in falls.
A brace which does not easily drop onto pins is an indicator that something is wrong. Itmay be that the brace is bent and must be discarded. Often, however, it means the scaffold is twisted and out of plumb. Braces should not be forced or hammered onto the pin. The condition causing this difficulty must be corrected so that the brace slides onto the pin easily. Adjusting screw jacks slightly will often solve this problem. However, make sure that the scaffold is not adjusted out of plumb to make a brace fit.
Coupling Devices
Every scaffold manufacturer provides coupling devices to join scaffold frames together in the vertical plane. These devices are sometimes omitted, with the belief that the bearing weight of the scaffold and its load will keep the frame above firmly resting on the frame below. This will probably hold true until the scaffold moves or sways. Then the joint may pull apart causing a scaffold collapse. Therefore, coupling devices must always be used and installed properly on every leg of the scaffold at every joint as assembly proceeds.
Wheels or Castors
If wheels or castors are used, they must be securely attached to the scaffold and equipped with brakes. Failure to properly attach wheels or castors to the frame has been the cause of many accidents involving rolling scaffolds. Ensure that the ground is level and free of potholes and other obstructions. Wheels or castors must have brakes which are well maintained and easily applied.
Platform Erection
All parts and fittings must be in place and secure before platform components are placed on a scaffold tier. When proceeding with the next tier, workers should lift platform sections or planks from the previous tier leaving either one platform section or two planks. While this requires more material, it speeds up erection because workers have platforms to stand on when erecting or dismantling the platform above.
Hoisting Materials
Where scaffolds will be more than three frames high, a suitable mechanical device will make the hoisting of materials easier during erection. While materials can be pulled up by rope , it is easier to rig a pulley system to the scaffold so that hoisting can be done by workers on the ground. This is much safer and eliminates the risk or workers falling from the scaffold platform as they pull materials up by rope. Ensure that you do not lift material in excess of the load capacity of the hoist system or the scaffold connection.
Dismantling
The dismantling of a scaffold proceeds in reverse order to its erection. Each tier should be completely dismantled and the material lowered to the ground before dismantling of the next tier begins. If platform sections or planks have been left at each level during erection, it is best to lower additional platform materials from above to the working deck being dismantled. Extra platform material can be lowered to the ground. Using this procedure, workers will be operating most of the time from a fully decked in platform. In addition to this, workers should be equipped with a safety harness and lifeline for securement to a suitable anchoring system, since guardrails will not always be in place as dismantling proceeds.
Removing jammed or rusted scaffold components can be a very hazardous operation. When scaffolds have been in the same location for a long time, pins and other components may rust, braces become bent and materials such as mortar or paint often build up on the scaffold parts. All of these can prevent components from separating easily. Tugging or pulling on stuck components can cause loss of balance leading to a fall. Workers should wear a safety harness and lanyard tied off to a secure anchor before attempting to loosen stuck or jammed parts. Do not hammer or pry apart the scaffold components. This may cause damage to the components and/or affect the structural integrity of the scaffold members.
Fall Protection
In most cases, a proper system of fall protection can be instituted for workers erecting and dismantling scaffolding. Often the scaffold is being erected on the side of a building or structure. In this case, a lifeline can be secured to a suitable anchor on the building and a fall arrestor (rope grab) attachment to a full body harness will protect the worker erecting the scaffolding.
Ladders
Whether built into scaffold frames, attached as a separate component or portable, ladders are an important means of access to scaffold platforms. Falls connected with climbing up and down scaffolds would be substantially reduced if adequate and properly erected ladders were always used.
There are four primary means of ladder access to a scaffold:
Climbing frames
Only scaffold frames having built-in ladders, as designed by the manufacturer for worker access, may be utilized. A major problem with ladders built into the frame is that planks sometimes stick out so far that it’s difficult to get from the ladder to the platform. This situation can be improved by using manufactured platform components which do not project beyond the end support, or using a properly secured portable ladder.
Portable ladders
Portable extension ladders may be used on the inside of frames or on the exterior of the scaffold, but they must be secured at the top and bottom. The ladder must be set-up in accordance with standard safe ladder practice.
Stand-off vertical ladders
A stand-off vertical ladders is also an acceptable means to access scaffolding, but should also be restricted to 5 metres (16.5 ft) in height, unless a proper ladder climbing fall protection system is provided.
Scaffold stairway systems
The best method for scaffold access is a stairway built into the scaffold structure. This provides for complete fall protection and also has built-in rest platforms. Rest platforms should be built so that the material cannot fall from one landing to the next.
Points to Remember:
Ladder rails should extend at least 1 metre above the platform level to facilitate getting on and off. Stepping on and stepping off the ladder at the platform level with no handrails can be dangerous.
Where scaffold frames are not equipped with ladder rungs, ladders must be installed as the erection of each tier proceeds.
Rest stations should be decked in on scaffold towers at intervals no greater than every 5 metres (16.5 ft). Climbing is strenuous work and accidents happen more frequently when climbers suffer from overexertion.
Ladders and Climbing
The ladder must be properly erected with rails projecting 1 metre (3.3 ft) above the platform of the scaffold. Debris, extension cords and tools should be cleared away from areas around the top and bottom of ladders. Both hands must be free to hold guardrails or ladder rails. Do not carry tools or materials by hand when climbing ladders. Wear a tool belt and pouch and move material up or down by rope. Three-point contact should always be used when climbing ladders. This means using two hands and one foot or two feet and one hand to maintain contact with the ladder at all times. Always face the ladder when climbing and always keep your center of gravity between the ladder rails.
The choice of a scaffold platform depends on the type of work being performed and the task being undertaken. Before a platform material is selected, an assessment must be made of the weight of workers, tools and materials to be supported by the decking.
Typical Loads and Requirements
Work platforms shall only be located on the top and bottom of end frames, not across intermediate braces. A standard minimum platform capacity is a uniformly distributed load of 50 lbs/sq ft for construction related work. This is usually sufficient for workers, their tools and equipment, and a moderate amount of light materials. (For example, two nominal 50 mm x 250 mm (2" x 10") SPF planks spanning 2.1 metres (7 ft) would have an estimated total capacity of about 600 pounds, enough for 2 workers and their tools).
This is insufficient for heavily loaded scaffolds such as those used for masonry construction. For masonry construction where large pallets of concrete blocks are to be carried, minimum capacity should be at least a uniformly distributed load of
150 lbs/sq ft. This means that scaffolds with spans of 2.1 metres (7 ft) should be at least double-planked. Aluminum/plywood platforms should also have a layer of scaffold planks on top.
Aluminum/Plywood Platform Panels
These platforms are combination wood and aluminum pre-manufactured decking, with special fastening hardware. The load-carrying capacity of these platforms has been determined by the manufacturer and should be marked on the platform. It may vary form one manufacturer to the other. The platform capacity should be verified before usage and workers notified as to the capacity.
The advantage of aluminum/plywood platform panels is that the decking can be easily replaced if damaged. One disadvantage is that the hooks on most models are subject to damage if dropped from the scaffold accidently during dismantling.
Platform hooks and fastening hardware must be checked regularly for looseness, cracking and distortion. Damage can occur if the platforms are dropped or thrown around carelessly. When used outdoors, these platforms should be secured to the scaffold frames. Otherwise, when left unloaded, they can be blown off the scaffold by strong winds.
Laminated Veneer Lumber
This material is a special type of exterior plywood rated by the manufacturer for scaffold use. The material is manufactured in large sheets of various thicknesses which can be sawn to the sizes required for different uses. The strength varies from manufacturer to manufacturer, depending on method of fabrication and species of wood used. Users of the material should ask suppliers to furnish rated working loads for the scaffold spans on which the lumber will be used.
In general, the material will be stronger than sawn lumber scaffold planks of similar size and species. The strength is also more uniform than sawn lumber. Like all lumber and plywood, laminated veneer lumber is subject to deterioration from weathering and rot. The planks must therefore be inspected routinely. Planks showing de-lamination, fungi or blisters should be removed from service.
Sawn Lumber Planks
Sawn lumber planks 50 mm x 250 mm (2" x 10") or larger have been the standard scaffold platform material for many years. They are readily available and the least expensive of the common platform materials. Planks must meet or exceed the requirements for No.1 construction grade of the species group used, which should be either spruce-pine-fir (SPF) or Douglas fir. Although the SPF group has less strength, it is usually lighter and therefore easier to handle than Douglas fir.
A minimum of two, 50 mm x 250 mm (2" x 10") scaffold planks are required on all working levels, unless it is a masonry scaffold, which requires a minimum width of 1.5 metres (or six 2" x 10" planks).
Scaffold planks must be cleated or other wise secured to prevent lateral movement. If there is a possibility of an upward force on the planks (i.e. wind load), then the planks must be secured against movement.
Since wood planks deteriorate they must be inspected on a regular basis and removed from service if inadequate. The jump test, commonly known as the "gorilla test", is NOT recommended. Such methods cause undetectable damage to the planks due to overstressing.
S awn Lumber Plank Inspection Criteria:
Scaffold planks must be examined prior to use on a scaffold and at regular intervals to ensure that the planks remain in safe condition.
1. Planks - The wood plank must be No. 1 construction grade lumber (S-P-F) Spruce-Pine-Fir, or better, nominal size 50 mm x 250 mm (2" x 10"). They must be properly seasoned and free from bow, crook, cup or twisted warp.
2. Splits - Planks with splits wider than 10 mm (3/8 ") or lengthwise splits closer than 75 mm (3 ") to the edge of the plank must be removed from service. When a lengthwise split in a plank exceeds 1/2 the length of the plank, then that plank should also be removed from service.
NOTE: Plywood cleats should NOT be used along the length of the plank to keep planks from splitting. It has been found that the cleats may cause the plank to rot beneath where the cleat has been fastened, due to moisture accumulation and retention. Scaffold planks with cleats should be inspected immediately and removed from service if there is any indication of wood rot.
Proper end cleats must still be used or prevent the plank from sliding off the scaffold frame.
3. Woodgrain - The grain is not to exceed a slope of 1 in 12 along the length of the plank.
4. Knots - Knots must be sound, tight, and spaced well apart. Maximum knot size for a 50 mm x 250 mm (2" x 10") plank is 50 mm (2 "). Knots on the edge of a plank must not be greater than 10 mm (3/8 ") width, or spiked across the entire width.
Scaffold planks can also be weakened by dry rot. This condition is not easily recognized in its early stages, especially if the exterior of the planks are weathered. Planks substantially infected with dry rot are usually lighter than normal and must NOT be used.
Failure to provide guardrails is one of the main reasons for falls from scaffold platforms. Manufacturers of standard scaffolds have guardrail components which can be attached to the scaffold frames. Where these are not available, guardrails can be constructed from lumber or tube-and-clamp components. In Manitoba, guardrails are required on all open sides of scaffold platforms in excess of 2.5 m (8 ft) in height.
Guardrails must be constructed to resist a force of at least 200 lbs. (900 Newtons) applied anywhere on the guardrail. If guardrails are composed of sawn lumber, the vertical members, top rail and mid-rail are to be made of 50 mm x 100 mm (2" x 4") lumber and the toeboard should be 25 mm x 150 mm (1" x 6"). The lumber used should be Number 1 construction grade SPF or better. The vertical wooden posts may be attached to the frame legs using U-clips or at least four "wraps" of No. 9 gauge wire with ends adequately twisted and secured.
Vertical cross-bracing is not considered to be a guardrail and must not be used in such a manner.
Tube-and-clamp guardrails may be constructed from standard aluminum scaffold tubing using parallel clamps to attach the vertical posts to each frame leg. Top rails and mid-rails should also be attached to the vertical posts.
Most manufacturers have toeboard clips to quickly and easily fasten toeboards to standard tubular posts on either frames or guardrail posts.
Guardrails Missing or Removed
There may be situations where scaffolds are not yet equipped or have had the guardrail removed. If the scaffold is more than one frame or tier in height (in excess of 2.5 m or 8 feet), personnel on the platform must tie-off with a safety harness and lanyard to a secure anchor.
Midrails and Toeboards
A midrail should be provided where necessary, especially if workers are kneeling or bending over often to do work. The midrail should have the same design capacity as the top rail.
Toeboards should be provided where there is a possibility of materials falling from the working level to a site below. The toeboard must be a minimum of 125 mm (5 ") in height.
Three-to-One Rule
The ratio of unsupported height to least lateral dimension on a scaffold should not exceed 3 to 1, unless the scaffold is:
1. tied-back to the structure at proper horizontal and vertical intervals
2. equipped with outrigger stabilizers to maintain the ratio of 3 to 1
3. equipped with a properly designed anchored guy wire system.
The 3-to-1 rule applies only to the extent that outriggers are extended symmetrically about the scaffold tower. If the outriggers are extended only on one side toppling is prevented only in that direction. Similarly, toppling is prevented on the opposite side only to the degree that the outriggers are extended. For situations like this which often occur in such operations as metal siding application, the 3-to-1 rule cannot be applied unless the scaffold is prevented from toppling to the side on which the outriggers are not fully extended. This means the scaffold must be erected against a structure or wall where the girts prevent the scaffold from toppling toward the building.
Outrigger Stabilizers
To maintain the 3 to 1 ratio, some scaffolds have outrigger stabilizers which may be attached to the scaffold base. With devices of this type, ensure that the outrigger is adjusted so that the foot will not be moved by vibration or dynamic loads on the platforms. Where stabilizers are used with castors, the castors must rest firmly on a solid surface with the stabilizer secured in the extended position before workers use the platform.
Tie-Back Requirements
Scaffolds which exceed the 3-to-1 rule must be tied in to a building or structure at intervals not exceeding 3 times the least lateral dimension of the scaffold. This usually means tie-ins are applied at every third frame vertically and every second frame horizontally for tubular frame scaffolds. Tie-ins for tube-and-clamp scaffolds should be applied at every second node vertically and every third standard horizontally. These tie-ins must be capable of sustaining lateral loads in both tension (pull) and compression (push).
There are a number of different tie-back methods, depending on the type and configuration of the supporting structure or building. These include anchor ties, reveal ties, box ties, through ties and others. In all cases, the system must be capable of supporting significant horizontal live and dead loads.
Tying-in with a couple of loops of #9 wire provides some support in tension but does not support a compressive load. While compression forces may only cause the scaffold to strike the building or structure, the movement may be sufficient to knock a worker off the platform. Tie-ins must be capable of withstanding both tension and compression forces and must have a positive securement at both the building face and scaffold frame.
It is not sufficient to use #9 wire tightened against a 50 mm x 100 mm (2" x 4") strut held against the structure, without a positive securement system. There must be a positive means of anchoring the strut to the building or structure.
The tie-in systems must be designed by a professional engineer where open scaffold heights exceed 15 metres (50 feet) and hoarded scaffolds exceed 7.5 metres (25 feet). Wire is not to be used in a tie-back system for securing scaffolding to a building or other structure, where the height of the scaffolding is greater than 15 m (50 ft.) . The tie-backs must sustain anticipated wind loads or dynamic loads caused by work being done on the scaffold. Tie-in design loads must be increased where heavy loads will be placed on the scaffold such as pallets of masonry materials. Hoarding increases the number of tie-backs to the building structure.
Hoarding/Tarps
Wind loads on a scaffold are another concern that affects tie-backs and bracing. These loads vary not only with speed but with the height and shape of structures where the scaffold is located and the exposure of the location. In addition, scaffolds which are going to be enclosed (hoarded) for winter construction or sandblasting will be subjected to significantly larger wind loads. An engineer must be consulted for the design and erection of all hoarded scaffolding greater than 7.5 m (25 ft.) in height.
Where scaffolding is completely hoarded, adequate ventilation must be provided to ensure worker protection when heating, sandblasting or other processes or procedures expose the worker to hazardous materials or agents.
Wind Uplift
Wind can lift lighter platform materials from the scaffold if they are not secured. Where severe wind conditions are anticipated or where high scaffolds are involved, platform materials such as aluminum/plywood panels should be secured to the scaffold. With some types of platform panels this may be done with wire or nails. Other pre-manufactured systems incorporate a sliding type locking device.
Scaffold Location
Checking the scaffold location thoroughly beforehand will eliminate many of the problems that develop during construction and will allow erection to proceed smoothly, efficiently and safely.
Before erecting a scaffold, check the location for:
1. ground conditions
2. overhead electrical wires
3.
obstructions
4. variation in surface elevation
5. tie-in locations and
methods
6. potential wind loading conditions
Overloading
Overloading scaffold platforms is one of the most frequent violations of good scaffold practice. Placing full pallets of bricks or concrete blocks on a single layer of 50 mm x 250 mm (2" X 10") scaffold planks is, in most cases, overloading the platform. Double planking on decks may be necessary where pallets of masonry materials are to be supported. Wherever possible, the pallets should be placed over the frame supports. In addition, planks used to support masonry materials should be inspected for damage or deterioration regularly .
Overloading may affect stability as well as load-carrying capacity. Differential settlement is often a problem where heavy loads are applied to scaffolds resting on uncompacted soils. A scaffold tower 9 metres (30 ft) high which settles 25 mm (1 ") on one side can move 150 mm (6 ") at the top. Settlement puts stress on braces, tie-ins and frame joints. Heavy loads should be placed symmetrically on the platform to ensure that soil settlement is uniform.
Finally, the scaffold structure must be capable of carrying the loads to be applied. Both light-duty and heavy-duty frames are available on the market. Light-duty frames should not be used where heavy loads will be involved. If the load-carrying capacity of the frames is not known, consult the manufacturer or supplier and obtain the load capacity of the scaffold frame system. The load-carrying capacity of frames usually varies with the height of the towers.
Rolling Scaffolds
Rolling scaffolds, other than those which are lifted off the ground on outriggers, must have brakes on all wheels. All brakes must be applied when the scaffold reaches the desired position. Scaffolds over one frame in height must not be moved while a worker is on the platform. If for some reason workers must remain on the platform when the scaffold is being moved, they should be tied off to an independent structure with a fall arrest system. The floor area where the scaffold is to be moved should be free of bumps or depressions and cleared of all debris. Rolling scaffolds must be securely pinned together and should always be fitted with horizontal bracing as recommended by the manufacturer. Scaffolds which are not securely pinned together can separate if they drop into a hole or depression or run into an obstacle at ground level. Horizontal bracing is necessary on a standard frame scaffold to keep it from folding up because the connections between frames and braces are essentially pinned joints.
Castors must be positively secured to the frame. Castors must be properly sized according to the manufacturers specifications. A castor dropping off in a hole or depression in floors can cause serious accidents and injuries. Each castor should have a brake which is in good working order and can be easily applied and maintained. The castors or wheels should be suitable for the surface on which the scaffold is to be used. Small wheels are suitable for pavement or concrete floors. Larger pneumatic wheels are necessary where soils are the working surface. Rolling scaffolds must always be used on a surface which is smooth, free of depressions and reasonably level.
Once again, workers should not be on a scaffold, when it is being moved.
Outriggers
Outriggers or stabilizers are used to provide base stability and maintain the 3-to-1 rule. They must be properly deployed and "snugged up" so that sufficient contact is made with the surface to prevent settlement or movement due to side thrusts. On soil the outrigger feet should always be placed on a mudsill.
Housekeeping
Scaffold decks are usually small, narrow and confined. Tools and materials to be used should be stored in an orderly fashion. Debris and waste materials should not be allowed to collect on the platform. It should be either put in a container or removed from the platform immediately. Waste pieces of lumber, pipe, wire and miscellaneous metal and small tools are tripping hazards which have caused many serious falls from scaffolds. Working safely on scaffolds requires keeping an orderly work area.
Scaffold systems and components should be inspected before each use to ensure structural stability. Some main areas to check for include:
1. damage to frames, braces and other structural
components
2. damage to hooks on manufactured platforms
3. splits,
knots and dry rot in planks
4. de-lamination in laminated veneer lumber
planks
5. compatibility of components
6. sufficient and proper
components for the job
7. scaffolding that has been in place for long
periods of time
Structural components that are bent, damaged or severely rusted should not be used. Similarly, platforms with damaged hooks should not be used. Planks showing damage should be discarded and removed from the site so that they cannot be used for platform material.
Bracing Components
Most bracing systems for tubular frame scaffolds are manufactured from light materials and are easily damaged. Braces with kinks, bends or deformation should NOT be used; such damage can significantly weaken them. The ends of braces are frequently damaged by dropping them on concrete or other hard surfaces during dismantling. Ends of braces are also frequently bent by forcing them onto the locking pin during erection. Constant bending can cause the ends to crack. Bracing ends should therefore be inspected before use and braces with cracked ends should be discarded. The scaffold supplier and/or Professional Engineer must certify the repair or replacement of any damaged components.
G L O S S A R Y
Definitions:
Mudsills - A minimum 50 mm x 250 mm (2" x 10") wood plank or other device used to support the scaffold frame base plates or other support devices.
Base Plates - A device used to support and distribute the leg load of a scaffold system sized according to the manufacturer’s specification.
Outrigger Stabilizers - A device used to extend the support length at the base of the scaffolding in order to provide stability against overturning.
Bracing - A system of members connecting frames or sections of scaffolding to make the scaffold structure and add strength and rigidity between members.
Tie-Backs - A reinforcing connection device which secures a scaffold to a fixed structure.
Hoarding - A product or material draped over scaffolding to protect workers from wind, rain and cold.
Guardrail - A rail secured to uprights and erected along the exposed sides and ends of platforms. MR189/85 section 22(1) stipulates that the minimum height of the guardrail shall be 900 mm (3 ft) and the maximum without incorporating a midrail be 1060 mm (3.5 ft). The guardrail should be wood or metal, but not a bracing component.
Platform - A working surface provided on a scaffold to support the weight of workers, tools and materials.
Planks - Refers to sawn lumber, 50 mm x 250 mm (2" x 10") or wider, used in creating scaffolding platforms. All lumber dimensions are nominal.
Fall Arrest Systems - A fall protection system that prevents serious injury or death of a worker due to a fall, usually consisting of a full body harness secured to a lanyard and lifeline.
Plumbness - Ensuring that the scaffold is balanced and erected at a 90 degree angle straight up from a level surface.
Coupling Devices - A connective device used to secure scaffold frames together.
Foundations - The surface upon which the scaffold is erected.
Toeboard - A barrier secured along the sides and ends of a platform to guard against the falling of materials or tools.
Engineering Design - The design of a scaffold system by a registered professional engineer, licensed to practise Engineering in Manitoba. The sealed drawings of a scaffolding system should includes all appropriate information on loading capacities and, detailing on tie-backs, foundations, etc. These drawings must be kept on site.
(source: government of Manitoba, Canada)