Roof width determination guidelines

Under 1926.501(b)(10), yes — a safety monitoring system alone may be used for roofing operations on low-sloped roofs that are 50 feet (15.25 m) or less in width. See the requirement in 1926.501(b)(10) and the non-mandatory guidance in Appendix A to Subpart M.

• Make sure the roof is low-sloped and the measured width of the roof area is 50 feet or less before relying on an SMS alone.
• Remember other applicable fall-protection requirements in 1926.501 still apply where relevant.

Under 1926.501(b)(10), the roof width on a simple rectangular roof is the lesser of the two primary overall dimensions when viewed from above. This is the rule shown in Example A of the Appendix A to Subpart M and relates directly to the requirement in 1926.501(b)(10).

• Measure the roof plan view (top-down).
• Use the shorter of the length or width as the roof area’s width for the 50-foot test.

Under 1926.501(b)(10), measure a sloped rectangular roof the same way as a flat rectangle: the width is the lesser of the two primary overall dimensions as viewed from above. Example B in Appendix A to Subpart M shows that sloping toward or away from the roof center does not change this method. See 1926.501(b)(10).

• Take a plan (top-down) measurement; do not measure slope length. The shorter primary plan dimension is the width.

Under 1926.501(b)(10), you must divide irregular or non-rectangular roofs into subareas and treat each subarea separately; the width of each subarea is the lesser of its two primary plan dimensions. Appendix A to Subpart M explains this approach (see Examples C and F) and supports the 1926.501(b)(10) requirement.

• Draw dividing lines to create subareas and measure each subarea from above.
• Use the shorter primary dimension of each subarea to test the 50-foot limit.
• Treat each non-contiguous roof area separately (see Example D).

Under 1926.501(b)(10), choose dividing lines of minimum length so as to minimize the size and number of subareas that might be 50 feet (15.25 m) or less in width. Appendix A to Subpart M explains this principle (see Example C) and ties back to the 1926.501(b)(10) provision.

• Aim to draw the shortest practical dividing lines to avoid creating unnecessary small areas.
• The intent is to limit how much of the roof can be covered by SMS alone, consistent with the standard.

Under 1926.501(b)(10), yes — separate, non-contiguous roof areas may be considered individual roofs and measured separately. This is shown in Example D of Appendix A to Subpart M and applies to the 1926.501(b)(10) allowance for safety monitoring systems.

• Measure each non-contiguous roof area on its own plan view and use the shorter primary dimension for the 50-foot test.

Under 1926.501(b)(10), treat penthouses, courtyards, and similar features by dividing the roof into logical subareas using minimum-length dividing lines so each subarea is measured on its own plan view. Appendix A to Subpart M shows this approach in Example E and supports the 1926.501(b)(10) rule.

• Draw dividing lines around the architectural feature to create subareas.
• Measure each resulting subarea's width (the shorter primary plan dimension) for the 50-foot test.

Under 1926.501(b)(10), "viewed from above" means you determine the two primary dimensions of a roof area using a plan (top-down) view, and the width is the lesser of those two plan dimensions. Appendix A to Subpart M explicitly states that the selected dimension is the lesser of the two primary dimensions as viewed from above and relates to the 1926.501(b)(10) requirement.

• Do not use slope length or elevation measurements for the width determination; use plan-view measurements.

Under 1926.501(b)(10), yes — if a roof subarea measures exactly 50 feet (15.25 m) in width (the lesser primary plan dimension), a safety monitoring system alone may be used for roofing operations on that area. See 1926.501(b)(10) and the guidance in Appendix A to Subpart M.

• Confirm the roof is low-sloped and all other conditions of the standard are met before using SMS as sole protection.

Under 1926.501(b)(10), Appendix A is non-mandatory guidance — it provides recommended methods and examples for measuring roof widths but does not itself add enforceable requirements. See the title and text of Appendix A to Subpart M and the applicable provision in 1926.501(b)(10).

• Employers may use the appendix methods to help comply with 1926.501(b)(10), but the underlying standard is the enforceable rule.

Under 1926.501(b)(10), you may subdivide a roof into subareas for measurement, but the intent in Appendix A to Subpart M is to use dividing lines of minimum length to minimize creating additional small roof areas where SMS alone would be allowed. See 1926.501(b)(10).

• Don’t artificially subdivide roofs to expand SMS eligibility; subdivisions should be logical and follow the appendix guidance.
• The goal is to limit the size of areas where SMS alone can be used, not to game the measurement rules.

Under 1926.501(b)(10), the allowance to use an SMS alone applies to low-sloped roofs 50 feet or less in width; roof slope matters because the standard specifically addresses low-sloped roofs. See 1926.501(b)(10) and the related guidance in Appendix A to Subpart M.

• If the roof is not low-sloped, the SMS-alone option under 1926.501(b)(10) does not apply; other fall protection methods must be used in accordance with 1926.501.

Under 1926.501(b)(10), measure each separate level or terrace as its own roof area (plan view) and use the lesser of the two primary plan dimensions for each area. Appendix A to Subpart M discusses roofs made of several separate non-contiguous areas (Example D) and supports the 1926.501(b)(10) approach.

• Treat each level independently for the 50-foot width test.

Under 1926.501(b)(10), practical steps are: map the roof plan, divide irregular roofs into logical subareas using minimum-length dividing lines, measure each subarea’s two primary plan dimensions, and use the shorter dimension to check the 50-foot limit. These actions reflect the guidance in Appendix A to Subpart M and the 1926.501(b)(10) requirement.

• Create a clear roof plan (drawing) showing dividing lines and dimensions.
• Verify the roof is low-sloped and each subarea meets the 50-foot or less test before relying on SMS alone.
• Keep documentation (measurements and diagrams) to show how widths were determined.

Under 1926.501(b)(10), yes — Appendix A to Subpart M provides Examples A–F that illustrate correct (marked W) and incorrect (marked @) ways to subdivide roofs and where to measure widths. See Appendix A to Subpart M for the illustrations and the related 1926.501(b)(10) requirement.

• Use the examples as a visual guide when planning subdivisions and documenting width measurements.