Appendix A

Scaffold Specifications

Appendix A of 29 CFR 1926, Subpart L, "Scaffolds," provides non-mandatory guidelines to assist employers in designing scaffold systems. However, these guidelines do not provide all the information necessary to build a complete system, and every scaffold must meet the requirements of 29 CFR §1926.451(a), which were covered earlier in this course.

The guidelines, which are summarized in the following slides, assume that all load-carrying timber members (except planks) of the scaffold are a minimum of 1,500 lb.-f/in² (stress grade) construction grade lumber. All dimensions are nominal sizes as provided in the American Softwood Lumber Standards, except that, where rough sizes are noted, only rough or undressed lumber of the size specified will satisfy minimum requirements.

Solid Sawn Wood and Allowable Spans

Solid sawn wood used as scaffold planks should be selected according to the grading rules established by a recognized lumber grading association or by an independent lumber grading inspection agency. In addition, planks should be identified by the grade stamp of the grading association or agency.

Allowable spans should be determined in compliance with at least one of the following:

• National Design Specification for Wood Construction published by the National Forest Products Association
• Paragraph 5 of ANSI A10.8-1988, Scaffolding Safety Requirements, published by the American National Standards Institute
• For 2 × 10 inch (nominal) or 2 × 9 inch (rough) solid sawn wood planks

Guardrails

Scaffold guardrails should meet the following criteria:

• Toprails should be equivalent in strength to 2-inch × 4-inch lumber, or
  • 1½-inch × 1/8-inch structural angle iron; or
  • 1 inch × .070-inch wall steel tubing; or 1.990-inch × .058-inch wall aluminum tubing.
• Midrails should be equivalent in strength to 1-inch × 6-inch lumber, or
  • 1¼-inch × 1¼-inch × 1/8-inch structural angle iron; or
  • 1-inch × .070-inch wall steel tubing; or
  • 1.990-inch × .058-inch wall aluminum tubing.
• Toeboards should be equivalent in strength to 1-inch × 4-inch lumber; or
  • 1¼-inch × 1¼-inch structural angle iron; or
  • 1-inch × .070-inch wall steel tubing; or
  • 1.990-inch × .058-inch wall aluminum tubing.
• Posts should be equivalent in strength to 2-inch × 4-inch lumber; or
  • 1¼-inch × 1¼-inch × 1⁄8-inch structural angle iron; or
  • 1-inch × .070-inch wall steel tubing; or
  • 1.990-inch × .058-inch wall aluminum tubing.
• Distance between posts should not exceed 8 feet.

In addition:

• Overhead protection should consist of 2-inch nominal planking laid tight, or 3/4-inch plywood.
• Screen installed between toeboards and midrails or toprails should consist of No. 18 gauge U.S. Standard wire 1-inch mesh.

To learn more about Scaffolding Safety visit our Construction Scaffolding Safety Online Training web page.