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Subchapter 4. Construction Safety Orders
Article 22. Scaffolds--Various Types

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§1647. Horse Scaffolds.

(a) General. (1) Lumber for construction of scaffolded horses shall be of "selected lumber" grade.

NOTE: The lumber sizes specified are nominal sizes for which standard finished sizes may be substituted. (See Plate B-41, Appendix.)

(2) The members of horses used for scaffolds shall be securely nailed or bolted together, and well braced to prevent collapse.

(3) The distance between the bottoms of adjacent legs measured perpendicular to the ledger shall be approximately 1/2 the horse height.

(4) The shimming of horse ledgers to obtain added height is prohibited.

(5) Horses or parts which have become weak or defective shall not be used.

(6) When horse legs are extended by splicing, the joints must be butt-ended, and scabs not less than 18 inches long and of the same cross section as the leg shall be nailed on each side of the joint. As an alternative, new legs of adequate length may be installed, provided that they completely overlap the original legs and are well secured to them from top to bottom. Vertical extensions shall not be used to extend height of metal folding horses if the stability of the horse is impaired.

(7) When arranged in tiers, each horse shall be placed directly over the horse in the tier below.

(8) On all scaffolds arranged in tiers, the legs shall be nailed down or otherwise secured to the planks to prevent displacement or thrust and each tier shall be substantially cross braced.

(9) Railings meeting the requirements of Section 1620 shall be installed on all open sides and ends of work platforms 7 1/2 feet or more above the ground, floor or level underneath.

(b) Light Trades.

(1) Horses for light-trade scaffolds shall have top horizontal members or ledgers of 2-inch by 4-inch lumber or material of equivalent strength, if the distance between the leg connections is 4 feet or less. Ledgers of 2-inch by 6-inch lumber or material of equivalent strength are required if the distance between the leg connections is greater than 4 feet but does not exceed 8 feet.

If the distance between leg connections exceeds 8 feet, the ledger strength must be increased in proportion to the amount by which the 8-foot distance is exceeded.

(2) The legs of horses for light-trade scaffolds shall be 1-inch by 6-inch lumber or material of equivalent strength for horses not exceeding 4 feet in height and 2-inch by 4-inch lumber or material of equivalent strength for horses between 4 feet and 10 feet in height. Horse scaffolds shall not be constructed or arranged more than two tiers or 10 feet in height.

(c) Heavy Trades.

(1) Horses for heavy-trade scaffolds shall have top horizontal members or ledgers of 3-inch by 4-inch lumber or material of equivalent strength, if the distance between the leg connections is 4 feet or less. Ledgers of 2-inch by 6-inch lumber or material of equivalent strength are required if the distance between the leg connections is greater than 4 feet but does not exceed 8 feet. If the distance between leg connections exceeds 8 feet, the ledger strength must be increased in proportion to the amount by which the 8-foot distance is exceeded.

(2) The legs of horses for heavy-trade scaffolds shall be 1-inch by 8-inch lumber or material of equivalent strength, for horses not exceeding 4 feet in height, and 2-inch by 4-inch lumber or material of equivalent strength, for horses between 4 feet and 10 feet in height.

(d) Collapsible Types.

(1) Collapsible horses constructed of well-braced frames hinged at the top may be used in place of the specified rigid horses, if construction is such that equivalent strength is provided.

(2) Adjacent legs of a collapsible horse shall be connected near the bottom with securely attached chains, hinged brackets, or other suitable links to prevent the legs from spreading beyond the distance intended. The height of collapsible horse scaffolds shall not exceed 6 feet.

(e) Platforms.

(1) Scaffold platforms shall not be supported by single horses having a total height exceeding 10 feet. Tiered horse scaffolds shall be limited to 10 feet in height made from no more than 2 tiers of horses. All horse scaffolds shall be substantially constructed and braced both transversely and laterally.

(2) Platforms shall be not less than 20 inches wide for light trades, and 4 feet wide for bricklayers, stonemasons, stone cutters, or concrete workers. Platforms used primarily by bricklayers or stonemasons shall extend to within 5 inches of the building face upon which the work is being performed. A single 2-inch by 10-inch plank may be used for light trades work up to a height of 4 feet.

(3) Planks used for platforms shall not be less than 2 inches by 10 inches, and the distance between supports shall not exceed 10 feet for light trades and 7 feet 6 inches for heavy trades.

(4) For horse scaffolds up to a height of 6 feet, platform planks shall not be more than 2 inches apart. Platform planks on higher scaffolds shall be laid closely together. Planks shall be of such length that they overlap the supports at each end by at least 6 inches. A plank shall not overlap an unsupported end of another plank. Unsupported projecting ends of planks shall be limited to an overhang of 18 inches or less.

(5) Douglas fir plywood that is 3/4 inch thick or thicker may be used for platforms if the panels are 4 feet wide or wider and are supported on cross members at 4-foot or closer intervals for light trades and 2-foot intervals for heavy trades.

(6) Provide standard ladder or other safe, unobstructed means of access to all work platforms.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.

HISTORY

1. Amendment of subsections (a) and (e) filed 11-14-75; effective thirtieth day thereafter (Register 75, No. 46).

2. New subsection (a)(9) filed 3-19-79; effective thirtieth day thereafter (Register 79, No. 12).

3. Amendment filed 7-24-87; operative 8-23-87 (Register 87, No. 33).

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