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Rooftop Warning Line Systems

Effective, efficient use of these fall protection systems

by Nick Kerber*This article is reprinted from Contractor's Guide November 1997 with additions and corrections by the author. 

Choosing Fall Protection

The federal government's fall protection laws (29 CFR 1926.501-.502) allow the following systems on roofs with slopes of 4:12 or less: 
 

TYPE OF SYSTEM PRACTICAL ASPECTS
Guardrails Requires substantial construction
Safety lines and harnesses Most practical when one man has a limited amount of work
Safety nets Difficult to build--they must extend 8 feet from the roof edge and withstand a 400# drop test
Warning line systems with safety monitors Flexible and relatively easy to set up
Alternative fall protection systems may be used if they can be shown to be effective.

This article is focused on warning line systems since they are the most common systems in use. These systems are popular because of their low cost, portability, and ability to adapt to most roof geometries. They rope off the perimeter of a work area with a line at about waist level, and operate on the principle that the line will warn workers that they are dangerously near the edges. 
         
Warning line systems consist of a flagged line that fences off a work area. The line is fastened to a series of stands that are set up near the edges of the roof. Efficient Use of Warning Line Systems - Quicksilver Engineering

(Fig. 1) If a liftbed truck is used to load the roof, warning lines may be run from the gates of the truck
to the warning line perimeter and a removable line used to tie off the area.


Work performed outside the warning line work area and near the roof edge is done with the aid of a safety monitor. The safety monitor alerts workers near the roof edge of danger and monitors their safety. Flat roofs less than 50 feet in width may be worked with only a safety monitor as fall protection. 

Efficient handling, a few tricks, and a smart game plan make an effective warning line system that reduces labor and increases production. 

Basic Requirements

A fall protection system using warning lines includes a perimeter line, means of access for men and material, and special details such as protection for workers near a hot pipe or a tearoff chute. 

The perimeter warning line is set up so that it is at least 6 feet from the roof edge. 

If a worker is operating equipment (such as a felt layer) toward an edge, the warning line must be at least 10 feet from that edge, giving an extra measure of safety. The flagged warning line must hang between 34 inches and 39 3/8 inches (1 meter) above the roof deck (flagline heights for California and Washington state codes presently differ from federal codes). 

Where loading or unloading exposes an edge, the requirements allow warning lines that properly contain the area and tie it off when not in use. Place a perimeter warning line stand even with each end of the exposed edge as part of perimeter system. Then run a warning line from each end of the exposed edge to the nearby stand to provide an access path.






A removable line is then tied between the two stands which allows the line to be removed during loading and replaced when loading is finished. The ladder area may be set up the same way. If a liftbed truck is used to load the roof, warning lines may be run from the gates of the truck to the warning line perimeter and a removable line used to tie off the area (see fig. 1).

If hoisting requires access to an open edge or if a rope and wheel is used, the receivers should be tied off and wear safety harnesses. A hot pipe may be set up to pump inside the work perimeter or it must be supported with an 8 foot guardrail (see fig. 2).

Efficient Use of Warning Line Systems - Quicksilver Engineering





Types of Stands

In the early days of warning line systems contractors often made stands using concrete filled tires with an embedded vertical steel post. They were heavy (100 pounds), bulky, and awkward to handle. 

The three types of stands now available are baseplate, cross-stand, and folding. 






Efficient Use of Warning Line Systems - Quicksilver Engineering

(Fig. 3) Baseplate Stands

Baseplate stands (see fig. 3) consist of a roughly square steel plate with a short length of pipe welded vertically at its center. The vertical post is a larger and longer piece of pipe that fits over the center pipe. These two-piece stands weigh from 45-60 pounds each and are available from several sources, most notably from kettle manufacturers. They're simple and durable and have stood the test of time. Their disadvantages include being relatively heavy, awkward to handle, and bulky to transport. The center pipe on the plate protrudes so that they won't stack compactly. They can be placed about 9 to a pallet but handling is laborious. 





Cross-stands (see fig. 4) have a base that looks like a cross. Two long steel bars are crossed with a pivot joint at the center. A post fits vertically on top of the joint and is fastened to the cross with a removable pin. When the post is removed, the bars can be pivoted together and the post placed on top of the bars, then repinned into a compact rectangular package for storage. These stands weigh about 37 pounds, stack compactly for transport, and include a convenient carrying handle. They are slow to assemble and disassemble in the field, and have a large base that lays in the work area. 
Efficient Use of Warning Line Systems - Quicksilver Engineering

(Fig. 4) Cross Stand






Efficient Use of Warning Line Systems - Quicksilver Engineering

(Fig. 5) Folding Stand

Folding stands (see fig. 5) consist of a post with 4 legs and a sliding ring that moves along the post. When the ring is pushed down the post, bars push each leg open much like the opening of an umbrella. A catch holds the stand open. Depressing the catch releases the sliding ring and allows the stand to be pulled closed into a compact, folded unit. These one-piece stands weigh about 24 pounds, set up and knock down quickly, and have a tilted post which keeps the base out of the work area. They don't lock in the folded position, and so must be stored horizontally.





Flaglines 

Flaglines are generally made of 3/16" rope with flags fastened every 6'. They are required to have a tensile strength of at least 500 pounds. Most systems are sold with flaglines made of polypropylene rope. 

Because polypropylene line loses its strength in the sunlight, weather and heat, it should be replaced each year. Polyester rope is a more durable line with excellent sun and weather resistance that can be expected to last many years. An inexpensive banner is sold by one manufacturer with a short life of approximately 1 month. 

Flags are generally made of a vinyl sheet glued to the rope. Vinyl flags crumple easily but relax in the sun. It's common for glued flags to become loose and slip down the rope. Loose flags can be refastened by clamping a stiff piece of wire around the top of the flag. 






Efficient Handling 

As with any other roofing operation, an efficient system needs to be developed that the workers can easily become proficient at. A warning line system is basically hundreds of pounds of stands that are handled several times by the end of the job.

Specifically, stands are loaded on a truck, hoisted up to the roof, positioned along the work perimeter, set up, repositioned during roofing operations, knocked down, carried to the hoisting area, transferred to the truck, and unloaded to storage.

Efficient Use of Warning Line Systems - Quicksilver Engineering

(Fig. 6) The use of carts to move stands can greatly
 reduce labor. 


An efficient system will transport easily, reduce handling and labor, set up quickly, make it easy to start the roofing work, allow the crew to work with as little interference as possible, and protect the workers. 

Handling stands on pallets and with insulation carts greatly reduces labor. A pallet of stands can be forklifted onto an insulation cart and the cart can be lifted onto the truck. The carts can be hoisted onto the roof at the job site. If a liftbed truck is used to load the roof, the carts can be rolled down a ramp onto the roof. 

Once on the roof, the carts can easily distribute the stands around the perimeter. After setup, the carts can be used for roofing operations. When roofing construction is finished, the truck is loaded with equipment and debris and lastly the carts are used to collect the stands and transport them for removal. 

Layout

The warning line system is laid out to make roofing as easy as possible. The location of the drains determines the initial setup. On roofs with drains inside the work perimeter, the stands are laid out as close to the edges as permissible and the drains and field are roofed. The stands are then pulled away from the edges a few feet and a safety monitor is used for all the edge work.. 

If the roof has the drains near the edges, you'll want to lay out the stands about 5 feet more than is permissible from the drain edges. If they ordinarily must be at least 6 feet from the drain edge, begin by setting them 11 feet from the edge. This will allow the crew to start work on the drains right away with the use of a safety monitor. When the drain edge is roofed up to the stands, the stands can be scooted 5 feet onto the finished roof and the fieldwork performed within the warning line area. When the field work is done, the stands are then pulled back from any remaining edges and these portions are roofed with a safety monitor. 

Work done with a safety monitor will be relatively inefficient. This is both because machine work is not allowed near the edge and the safety monitor is fairly idle. Limit the area of work done at the edges with a safety monitor to the least amount possible. 

Layout is begun by setting up stands 40 feet apart along the perimeter. The flagline is tied from stand to stand so that its low point at midspan is at least 34" off the deck. 

There is a misconception in the industry that stands should be laid at 25 foot intervals. This practice probably began early in the use of warning line systems when manufacturers sold 100 feet of flagline with 4 stands. There is no OSHA guideline for spacing between stands. 

The proper distance between stands is determined by the ability of the stands to support the weight of the flagline and can be found by experimenting with different spacings in the field. As the stands are placed further apart, the flagline exerts increasing overturning force on the stands. If the stands are placed too far apart the force on the stands will make them unstable, and the roofers will fight with them as they work around them and move them. All stands are made almost equally stable to meet OSHA specifcations. Testing shows that two stands can be set up to 65 feet apart without the flagline tipping them over. Placing the stands closer together makes them easier to use. A 40 feet spacing is a good compromise between using as few stands as possible and making the system easy to work with. Spacing the stands 40 feet apart is not an inflexible guideline. If the dimensions of the roof are such that setting stands 45 feet apart results in a cleaner setup, 45 feet will work well enough. On the other hand, setting stands 25 feet apart will result in deploying 60% more stands, each handled many times, resulting in excessive labor and purchase costs. 

Flaglines can be handled quickly and easily on a reel. The reel eliminates hand coiling the line and the inevitable tangles and knots that come with it. If you don't have reels, electrical reels will work well and can be purchased cheaply at your local hardware store. Handle the flagline from a reel in the following way: After the stands have been laid out, tie one end of the flagline to a stand. Walk the reel to the next stand, paying out line by keeping slight tension on the reel. The line is tied to the next stand and then that stand is kicked slightly, inching it in one direction or another to fine tune the height of the flagline at midspan to near 34" above the roof deck. The flagline is tied and adjusted in this way to each stand in succession. 

Another tip is to add extra rope at corner stands to make moving the stands easier. When a line of stands are moved to work on an edge, the extra line provides slack so that each stand can be moved to its new position without untying each stand. To add extra line to a corner stand, first tie the line to a corner stand, coil an extra 8 feet of the flagline, retie the line, then set the coil on the post. 






Typical Warning Line Set Up

Here's a warning line system layout for a hotjob. The roof is a 100'x200' shed roof, 12' high, with a 1/2:12 slope. Hoising access, ladder access, and a hot pipe are included.

All the drains are on the bottom edge. It's desirable to load the roof and place the kettle near the top edge. A liftbed truck can be raised near the top edge and the ladder near one rail of the truck to consolidate access. Machine work will run in the long direction.

For fieldwork, the warning line will be set 6' from the bottom and top edges and 10' from the sides. The fieldwork area will be 88'x180'. The sides each require 88'/40'=2.2 stands. Two stands can be used with a 44' spacing for each side. The bottom and top edges require 180'/40'= 4.5 stands. Five stands can be used with a 36' spacing for the bottom and for the top. Add 2 more stands for the truck and ladder access detail. Total stands=2+2+5+5+2=16 stands. A warning line can be tied at stand #1 and run in the direction of stand #2. This line can then provide a removable access to the loading and ladder area by untying or tying at stand #1. The system is initially set up 11' from the bottom edge on line A with 8' of extra line at the corner stands. The crew roofs the bottom edge up to the stands with a safety monitor, then moves the bottom line of stands down 5' to line B on the finished deck. The crew then roofs the field up to line C. Finally the crew pulls the side and top lines in 5' to lines D, E, & F and finishes the rake and top edges with a safety monitor. This completes the roof.

Efficient Use of Warning Line Systems - Quicksilver Engineering





Knockdown

When the job is finished, the warning line system is knocked down. First one end of the flagline is untied and the flagline is reeled in under tension while walking from stand to stand. A cart is used to gather each stand as it is knocked down. The filled cart is removed by either hoisting it down or rolling it into the truck. 

An efficient warning line system reduces labor, gives the crew a quicker start, and becomes an integral part of the job. As a roofing crew masters the use of a warning line system, they focus more on building the roof and fall protection takes its natural supporting role of enhancing safety. 

Nick Kerber has 20 years roofing experience, is a professional engineer, and is president of Quicksilver Engineering. For questions, or to share safety tips and OSHA experiences, Mr. Kerber can be reached at (541)459-5571 or by e-mail.