Appendix B: Individual Scaffolds

• Supported Tube & Clamp
• Frame or Fabricated (Planked)
• Ladder Jacks
• Boatswain Chair
• Roof Brackets
• Horse Scaffold
• Step Platform, and Trestle Ladder Scaffolds
• Rolling Scaffolds

Supported Tube & Clamp (top)

Tube and coupler/clamp scaffolds are so named because they are built from tubing connected by coupling devices. Due to their strength, they are frequently used where heavy loads need to be carried, or where multiple platforms must reach several stories high. Their versatility which enables them to be assembled in multiple directions in a variety of settings, also makes them difficult to build correctly.

Requirements
When platforms are being moved to the next level, the existing platform must be left undisturbed until the new bearers have been set in place, and braced before receiving the new platform.

Couplers/clamps must be made of a structural metal, such as: drop-forged steel, malleable iron, or structural-grade aluminum.

The use of couplers made from gray cast iron is prohibited.

Tube and coupler scaffolds greater than 125 feet in height must be designed by a registered professional engineer, and constructed and loaded in accordance with that design.

Bracing
Transverse bracing forming an "X" across the width of the scaffold must be installed at the scaffold ends, and at least at every third set of posts horizontally (measured from only one end), and every fourth runner vertically.

Bracing must extend upward diagonally to opposite sides of the scaffold, such as from the inner posts or runners to the next outer posts or runners, or vice versa.

Building ties must be installed at the bearer levels between the transverse bracing.

On straight run scaffolds, longitudinal bracing across the inner and outer rows of posts must: be installed diagonally in both directions, and extend upward from the base of the end posts to the top of the scaffold at approximately a 45-degree angle.

On scaffolds whose length is greater than their height, longitudinal bracing must be repeated beginning at least at every fifth post. On scaffolds whose length is less than their height, longitudinal bracing must be installed from the base of the end posts upward to the opposite end posts, and then in alternating directions until reaching the top of the scaffold.

Bracing must be installed as close as possible to the intersection of the bearer and post or runner and post.

Where conditions do not permit the attachment of bracing to posts, bracing must be attached to the runners as close to the post as possible.

Bearers
Bearers must be installed transversely between posts. When bearers are coupled to posts, the inboard coupler must bear directly on the runner coupler, and be as close to the posts as possible.

Bearers must extend beyond the posts and runners, and provide full contact with the coupler. The bottom bearers must be located as close to the base as possible.

Runners
Runners must be installed along the length of the scaffold, located at level heights on both the inside and outside posts.

On outside posts, tube and coupler guardrails and midrails may be used in lieu of outside runners.

Runners on straight runs must be interlocked to form continuous lengths, and coupled to each post. The bottom runners must be located as close to the base as possible.

Recommended Guidelines

Minimum Size of Members
	Light Duty	Medium Duty	Heavy Duty
Maximum Intended Load	25 Pounds/ foot2	50 pounds/foot2	75 pounds/foot2
Posts, runners, and braces Note: Longitudinal diagonal bracing must be installed at an angle of 45° (±5°)	Nominal 2 inches (1.9 inches) OD steel tube or pipe	Nominal 2 inches (1.9 inches) OD steel tube or pipe	Nominal 2 inches (1.9 inches) OD steel tube or pipe
Bearers Note: Bearers must be installed in the direction of the shorter dimension.	Nominal 2 inches (1.9 inches) OD steel tube or pipe and maximum post spacing of 4 feet X 10 feet	Nominal 2 inches (1.9 inches) OD steel tube or pipe and a maximum post spacing of 4 feet X 10 feet. or Nominal 2½ inches (2.375 inches) OD steel tube or pipe and a maximum post spacing of 6 feet X 8 feet.	Nominal 2½ inches (2.375 inches) OD steel tube or pipe and a maximum post spacing of 6 feet X 6 feet.
Maximum runner spacing vertically	6 feet 6 inches	6 feet 6 inches	6 feet 6 inches

Frame or Fabricated (Planked) (top)

Fabricated frame scaffolds are the most common type of scaffold because they are versatile, economical, and easy to use. Many University personnel frequently use them in one or two tiers, but their modular frames can also be stacked several stories high for use in large-scale construction jobs. NOTE: The regulations contained in sections 2 – 6 address Pre Fabricated Frame scaffolds.

A ladder jack scaffold is a simple device consisting of a platform resting on brackets attached to a ladder. Ladder jacks are primarily used in light applications because of their portability.

Support

All ladders used to support ladder jack scaffolds must comply with 1926 Subpart X (Stairways and Ladders).

Job-made ladders must not be used to support ladder jack scaffolds.

Ladder jacks must be designed and constructed to bear on the side rails and ladder rungs, or the ladder rungs alone.

If ladder jacks bear on the ladder rungs alone, the bearing area must include a length of at least 10 inches on each rung.

Ladders used to support ladder jack scaffolds must be placed to prevent slipping, fastened to prevent slipping, or equipped with devices to prevent slipping.

Platforms should not be placed higher than 20 feet from the supported base, and platforms must not be bridged together.

Recommended Guidelines

• Ladder jack scaffolds have a maximum intended load of 25 pounds per square foot.
  
• No more than two individuals may occupy any platform at one time.
  
• The maximum span between supports is 8 feet.

Boatswain Chair (top)

Boatswain's chair tackle must consist of:
Correct-size ball bearings or bushed blocks containing safety hooks, and properly eye-spliced first-grade manila rope, or other rope of equivalent strength, durability, etc.

Seat Slings

Seat slings must pass through four corner holes in the seat, cross on the underside of the seat, be rigged to prevent slippage which could cause the chair to be out-of-level, and be at least 5/8-inch diameter fiber, synthetic, or other first-grade manila rope of equivalent criteria (strength, slip resistance, durability, etc.).

Non-cross-laminated wood chairs must be reinforced on the underside with cleats to keep the board from splitting.

Wood seats for boatswain's chairs must not be less than 1 inch thick (if made of non-laminated wood), or 5/8-inch thick (if made of marine-quality plywood).

Roof Brackets (top)

Scaffold brackets must be constructed to fit the pitch of the roof and provide a level of support for the platform.

Brackets must be anchored in place by nails unless it is impractical to use nails. When nails are not used, brackets must be secured with first-grade manila rope of at least ¾-inch diameter, or equivalent.

Horse Scaffold (top)

Scaffolds must not be more than 10 feet or two tiers in height, whichever is less.
When horses are arranged in tiers each horse must be placed directly over the horse in the tier below. The legs of each horse must be nailed down or otherwise secured to prevent displacement and each tier must be crossbraced.

Recommended Guidelines

Scaffold platforms must be placed no higher than the second-highest rung or step of the ladder supporting the platform.

All ladders used in step, platform and trestle ladder scaffolds must meet the requirements of 1926 Subpart X (Stairways and Ladders), except that job-made ladders are not permitted. All ladders must be prevented from slipping by how they are placed, fastened, or equipped. Scaffolds must not be bridged one to another.

• Height of the tower must not exceed four (4) times the minimum base dimension. Outrigger frames or outrigger units may be used to increase base width dimension when necessary.

• All casters must be secured to frame legs or screwjacks with a nut and bolt or other secure means. Weight of tower should not exceed the capacity of the casters.

• Screwjacks must not be extended more than 12 inches above caster base. Tower must be kept level and plumb at all times.

• Horizontal/diagonal bracing must be used at the bottom and top of tower and at intermediate levels of 20 feet. Fabricated planks with hooks can be used to replace the top diagonal brace.

• All frames must be fully cross-braced.

• Only prefabricated plank or cleated plank should be used.

• Casters must be locked at all times, except when the scaffold is in motion