Warning Lines on RoofWarning lines are one of the oldest forms of fall protection mandated by OSHA for low slope roof projects. The basics of the system are that the lines must be made of rope, wire or chain. The flags must be visible, present every six (6) feet, 34 to 39-inches from roof level and erected at a minimum of six (6) feet from the fall hazard.

Warning lines are generally thought to be a means of fall protection for the unprotected edge. However, warning lines can be used to establish a barrier for multiple rooftop fall hazards. The warning line system continues to be a versatile tool in the roofing industry even with the increasing use of temporary guardrails and engineered systems. 

Prior to commencement of any roofing project, a warning line system is established to create a working perimeter for the crews. The bright yellow flags provide the crews with a clear indicator of their distance from the unprotected edge. This perimeter allows the crews to work freely and limits the need for additional fall protection systems for a large portion of the project.

Once access/egress to roof level has been determined and the work perimeter erected, a clear indicator of where to access/egress must be established.  Warning lines can be used to accomplish this task as well.

Warning lines may also be set up to establish a walkway to the intended scope of work. These warning lines provide roofers with a clear path of travel to the main work area. Using the warning lines this way allows crews to steer clear of hazards at roof level, such as skylights, areas where the decking is suspect and customer specific equipment.

Warning lines are often used to flag-off skylights in the main work area. This provides the crews with an understanding of how close they can get to skylights before additional means of fall protection is required such as conventional fall protection systems.

An underdeck inspection is conducted when bidding roof projects. One of the main reasons for this inspection is to locate potential areas of deteriorated decking. The areas of deteriorated decking may fall within areas of the proposed scope of work or paths to the perspective work area. There are limited cases where a majority of the decking must be replaced due to degradation, but these areas are isolated in most cases. 

Warning lines can be used to make the crews aware of these isolated locations at roof level. Warning lines are a clear indicator of the perimeters where you can work before conventional fall protection is necessary. 

The warning line system was established as one of the earliest forms of fall protection. However, unlike the body belt, there are still many uses for the warning line system in modern day rooftop safety.

Safety at CentiMark

Safety and injury prevention are our responsibility at CentiMark. We provide you with the latest safety products and advancements to protect your building and the people inside it. Prior to the start of any roofing or flooring project, we review all safety plans with our customers and crews. Our goal is for all CentiMark associates to return home safely to their families every evening.


About National Safety Stand Down:

The National Safety Stand Down is organized by the Department of Labor to prevent falls in construction. ​Fatalities caused by falls from elevation continue to be a leading cause of death for construction employees, accounting for 370 of the 991 construction fatalities recorded in 2016 (BLS data). Those deaths were preventable. The National Safety Stand Down raises fall hazard awareness across the country in an effort to stop fall fatalities and injuries.

Blog contributed by Robert Wilson, CentiMark Northern Safety Manager, Franklin, OHby Robert Wilson, CentiMark Northern Safety Manager, Franklin, OH