OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

January 16, 2001

Mr. Craig D. Adams
Safety and Health Agenda
For Roofing Professionals
4840 West 15th Street
Suite 1000
Lawrence, KS 66049-3862

Re: 1926.501(b)(10), 1926.502(h), Subpart M, Low-Slope Roof, Safety Monitoring System

Dear Mr. Adams:

This is in response to your December 2, 1999 letter to the Occupational Safety and Health Administration's (OSHA) Kansas City Regional Office. You ask several fall protection questions regarding how breaks in elevation on low-slope roofs affect safety monitoring system requirements under 29 CFR Subpart M (fall protection for construction). We apologize for the long delay in providing this response.

We have paraphrased your questions as follows:

Question 1: For roofing work, OSHA's fall protection standard allows use of a safety monitor to satisfy fall protection requirements on low slope roofs less than 50 feet wide. Examples D and E of 29 CFR 1926 Subpart M, Appendix A, give examples of how to calculate the width of various configurations of roofs. Some of these examples use breaks in elevation as a dividing line to determine roof width. Is there a minimum height for considering a change in elevation to qualify as a dividing point on the roof?

Background: Low-Slope Roof-Safety Monitoring Systems
29 CFR 1926.501(b)(10) permits employers to protect employees engaged in roofing activities on low-sloped roofs from falling by several means, one of which is the use of a safety monitoring system in combination with a warning line system. However, §1926.501(b)(10) further provides that:

"...on roofs 50-feet (15.25 m) or less in width, the use of a safety monitoring system alone [i.e., without the warning line system] is permitted."



In such situations, OSHA allows the use of a safety monitoring system alone because of the limited roof area in which work could be performed.

Determining the roof's width
Appendix A to subpart M contains non-mandatory guidelines for complying with §1926.501(b)(10). It shows several roof plans indicating where the roof or roof area is to be measured for purposes of determining whether the width is under 50 feet. In each of the plans, irregularly shaped roofs are divided into regularly shaped areas, keeping the dimension selected to the lesser of the two primary overall dimensions. In your letter, you specifically refer to examples D and E, pictured below:



Figure showing separate non-contiguous roof areas
Example D Separate Non-Contiguous Roof Areas


Figure showing roofs with penthouses, open courtyards, additional floors, etc.
Example E Roofs with penthouses, open courtyards, additional floors, etc.


Dividing Lines; Breaks in roof elevation
The roof plans shown in Appendix A are viewed from above, looking down onto the structure. Example D indicates that, where roofs of several adjoining structures are separated by low walls (for example, a firewall parapet), such as on older style townhomes, employers may use those low walls or small breaks in elevation to constitute a division in the roof area. Example E demonstrates how to subdivide roofs to allow for penthouses, additional floors, courtyard openings and other architectural features creating changes in elevation.

Apart from the non-contiguous roofs in Example D, as stated in paragraph (2), the general rule is to use dividing lines "to minimize the number of roof areas where safety monitoring systems alone are [permitted]."

Your question is whether there is a minimum height for using a parapet wall as a dividing line between roof sections or a minimum change in elevation when applying these examples. For purposes of determining roof widths, neither the standard itself nor Appendix A sets a minimum height for a change of elevation or dividing parapet wall. So, with respect to dividing roof sections using parapet walls as the dividing line, as in Example D, the answer is no — there is no minimum height for such a wall. With respect to Example E, any change in elevation may be used as a dividing point for purposes of determining the widths of roof areas.

In short, as examples D and E of the Appendix show, roofs on different levels will be treated as separate roofs, and widths are to be determined for each such roof. Also, as long as the roofs that are divided by parapet walls are indeed separate, roof widths are determined for each such roof, and there is no minimum height requirement for the dividing wall.

Question 2: On a low-slope roof, greater than 50 feet wide, with an elevation change up to another level, or an architectural feature such as a firewall, what height would the change in elevation (or wall) need to be for OSHA to consider it as providing fall protection for workers on the lower level?

Response: First, a change in elevation or a firewall 42 inches high (plus or minus 3 inches) would meet the guardrail requirements of §.502(b)(1), and thus provide fall protection for the workers on the lower level.

Second, where the change in elevation or firewall is less than guardrail height, the question becomes quite complex, because you have specified neither the elevation (or firewall) height nor the distance to the edge of the upper roof (or edge of the portion of the roof beyond the firewall). While there may be situations where a break in elevation is sufficient to prevent exposure to falls from the higher level, there are too many variables for us to give a categorical answer without additional details. The relevant variables would include these heights and distances and the extent to which the elevation change or firewall posed a physical barrier to going onto the upper level or beyond the firewall.

If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.


Russell B. Swanson, Director
Directorate of Construction

[Corrected 6/2/2005]