Proper Scaffold Erection
Scaffolding must be erected, altered, moved, and dismantled in accordance with applicable OSHA standards and under the supervision of a scaffold competent person. Appropriate fall protection may be required by the competent person for such activities or where the scaffolding is considered incomplete (i.e. missing parts due to area obstructions).
Scaffold components cannot be mixed if they are from different manufacturers unless they fit together without force. Scaffold components of dissimilar metals should not be used together, unless the competent person has determined that galvanic action will not reduce the strength of any component.
Supported scaffold poles, legs, posts, frames, and uprights shall bear on base plates and mud sills (or other adequate firm foundation). The size of the mud sill shall be based on the type of soil the scaffold will be erected upon.
|Scaffolds 4 levels or less in height||2" x 10" pad, 12" - 18" long|
|Scaffolds > 4 levels on Type A Soil||2" x 10" pad, 18" long|
|Scaffolds > 4 levels on Type B Soil||2" x 18" x 18" pad|
|Scaffolds > 4 levels on Type C Soil||2" x 36" x 36" pad|
The base and mud sill must provide a solid surface for the feet to sit upon so that the scaffold doesn't sink, move, settle, or shift. Unstable objects, such as bricks, cinder blocks, buckets, scrap lumber, etc., shall not be used to support or level scaffolds. Screw jacks must be used to level scaffolding on uneven surfaces. The maximum extension for a screw jack is 18 inches high. Most screw jacks will have a built-in stop so that the maximum height cannot be exceeded. (For mobile scaffolds, the maximum height of the screw jack is 12 inches.)
Supported scaffold poles, legs, posts, frames, and uprights shall be plumb (i.e. perfectly vertical) and braced to prevent swaying and displacement. Crossbracing is required on both front and back sides of each scaffold buck or frame.
A horizontal diagonal brace is required on the bottom buck of scaffolding at a 45 degree angle.
To check a scaffold for being plumb, use a level on two opposite uprights. To make sure the scaffold is level, use a level on a horizontal support or bearer. To ensure the scaffold is "square", use a tape measure and measure the distance between opposite corners. The two measurements should be equal.
Scaffold frames (i.e. bucks) must be joined together vertically by coupling or stacking pins (or equivalent means).
Scaffolds with a height-to-base width ratio of more than four to one shall be restrained from tipping over by guying, tying, bracing, or equivalent means. Guys, ties and braces shall be installed where horizontal members support both inner and outer legs. Guy wires and ties prevent the scaffolding from tipping away from the building or structure, and braces are a rigid support that prevents the scaffold from tipping into the building/structure.
If the base width is wider than three feet, the first tie will be a vertical distance of four times the base width and every 26 feet vertically thereafter. For example, if the base width is 5 feet, the first vertical tie will be (5 feet x 4) 20 feet from the ground.
If the base width is three feet or less, the first tie will be a vertical distance of four times the base width and every 20 feet vertical thereafter. For example, if the base width is three feet, the first vertical tie will be (3 feet x 4) 12 feet from the ground.
For long (running) scaffolds, guys, ties, and braces shall be installed at each end of the scaffold and at horizontal intervals not to exceed 30 feet.
Platform/decking planks may be made of solid sawn wood, manufactured wood, manufactured steel, or manufactured aluminum. If solid sawn wood is used, it must be scaffold grade.
- Note: Once a plank has been used as a mud sill, it cannot be used as decking again.
Scaffolds must be fully planked or decked whenever possible. The space between the last plank and the uprights cannot exceed 9 1/2 inches. The space between planks cannot exceed 1 inch, except where necessary for obstructions. Platforms and walkways, in general, must be at least 18 inches wide.
Where the platform will not be more than 14 inches from the face of the work (18 inches for plastering and lathing operations), fall protection is not required. The face of the work (ex. the side of a building) basically serves as the fall protection system.
The ends of each platform must be cleated or restrained by hooks (or equivalent) to prevent accidental displacement, or must extend at least 6 inches over the centerline of the support.
- The maximum extension of the plank cannot be more than 12 inches for planks that are 10 feet long or less.
- For planks that are greater than 10 feet long, the maximum extension past the centerline of the support is 18 inches.
- Where platforms overlap to create a running scaffold, the overlap must occur only over a support and shall not be less than 12 inches unless nailed together.
Where a platform changes direction (ex. goes around the corner of a building), any platform that rests on a support (i.e. bearer) at an angle other than a right angle, shall be laid first. Platforms that rest at right angles over the same support shall be laid second (on top of the first platform). The objective is to reduce the tripping hazard by having the ends of the top layer of planks form a straight line, rather than a saw-toothed edge, which increases tripping hazards.
Wooden platforms (i.e. decking, planks) must not be painted to hide defects. They may, however, be treated periodically with clear preservatives, fire-retardants, and/or slip-resistant finishes.
Proper access must be provided to access the work platform of the scaffold.
- Ladders that are a part of the scaffolding system, such as hook-on and attachable ladders, shall be positioned so that the bottom rung is not more than 24 inches above the supporting level.
- Portable extension ladders used to access the work platform must meet OSHA design and use criteria, which includes securing the ladder to the scaffold at the top and bottom and having the ladder extend at least three feet past the landing surface. Ladders must also be positioned so as not to tip the scaffold.
- Stairtowers must have hand and midrails on each side of the stairway. Stairs must be at least 18 inches wide and have a landing platform at least 18 inches long at each level. Stair treads must be of slip-resistant design. The riser height must be uniform, and the stair angle must be between 40 and 60 degrees from the horizontal.
- Where the frame of the scaffold will be used for access, the manufacturer must specify in writing that it was designed for such purposes. Design features include a rest platform every 35 feet, rungs at least 11 1/2 inches wide (8 inches for ladders built into the frame), and uniform rung spacing not exceeding 16 3/4 inches.
At Virginia Tech, a fall protection system (i.e. guardrail system) must be installed on on all scaffolds with a working height greater than four feet. The guardrail system shall be installed along all open sides and ends of the platform before being used as a work platform by employees. One exception is when the scaffold platform is within 14 inches of the face of the work.
Top rails (manufactured after 1/1/2000) must be between 38 - 45 inches above the platform surface. (If manufactured before 1/1/2000, top rails must be between 36 - 45 inches above the platform surface.) Top rails must be capable of supporting at least 200 pounds applied in a downward or outward direction.
- Note: Crossbracing is acceptable in place of a top rail when the crossing point of the two braces is between 38 - 48 inches above the work platform. It cannot serve as both a midrail and a top rail.
Midrails must be installed at a height approximately midway between the toprail and the platform surface. Midrails must be capable of supporting at least 150 pounds applied in a downward or outward direction.
- Note: Crossbracing is acceptable in place of a midrail when the crossing point of the two braces is between 20 - 30 inches above the work platform. It cannot serve as both a midrail and a top rail (as incorrectly done in this picture).
Personal Fall Arrest Systems
The scaffold competent person must determine personal fall protection requirements for employees performing erecting or dismantling activities, and for scaffold users if the scaffold is incomplete for any reason. Personal fall protection must be required and provided by the employer where the installation and use of such protection is feasible and does not create a greater hazard.
Personal fall arrest systems used on scaffolds are required when the guardrail system is incomplete or does not provide adequate protection. Lanyards or connecting devices must be connected to a vertical lifeline (1st choice), a horizontal lifeline (2nd choice), or a structural member of the scaffold (last choice).
Falling Object Protection
Toeboards must be installed on work platforms where materials or tools will be in use. Toeboards must be installed not more than 1/4 inch above the platform and securely fastened. They may be made of solid material or mesh with openings no greater than 1 inch. Toeboards must be capable of withstanding at least 50 pounds applied in a downward or outward direction.
Nets and Platforms
Additional protection from falling debris and other small objects must be provided in areas where personnel will be in the vicinity of scaffolds. Such protection may be in the form of:
- Barricades to keep personnel out of a hazardous area,
- Screens which are erected between the toe board and hand rail of the work platform,
- Debris nets to catch materials before they hit the ground, or
- Canopy structures made of solid materials.
Large or heavy materials stored on the scaffold platofrm must be located away from the edges of the work platform and secured, if necessary.
Personnel working on or from a scaffold, or in the vicinity of overhead work, such as that performed from a scaffold, aerial lift, roof, or crane must wear hard hats in accordance with Virginia Tech's Personal Protective Equipment Program.