Getting Pipe Staging Right - Continued

Engineered (laminated) lumber scaffold planks and proprietary system platforms cost more than regular framing lumber, but are well worth the extra money. Work platforms manufactured from aluminum or plywood and steel use integral hooks to connect to the frame, helping to hold it square. The hooks typically include an additional means of locking to prevent wind uplift, a real concern. Strong winds can cause stacked frame sections to separate vertically, which is why you never want to omit the toggle pins that secure the coupling pins on both sides of connected frames (Figure 8). No component in the system should be thought of as optional or unnecessary.

Figure 8Wind uplift and frame separation are serious concerns. Never omit the toggle pins that secure both ends of the couplers between frames.

Safety guidelines require that every working level be fully planked from one side of the scaffold to the other, with no gaps greater than 1 inch. Proprietary planks and platforms are sized to conform to this standard when used in multiples. Toeboards prevent loose materials from falling off the work platform and have to be at least 4 inches high. You can buy or rent a metal version, but we simply lean staging planks on edge along the frames' uprights and wedge them against the last plank on the platform (Figure 9).

Figure 9.Falling objects present a huge safety hazard on the job site. Toeboards prevent tools and materials from being knocked off the scaffold and should always be installed before loading and using the platform. Full-width planking prevents both drops and falls.

Side arms and end arms extend the width and length, respectively, of the work platform. We regularly use side arms to offset workers toward the wall and we use the main platform to stage materials and mortar trays (Figure 10). Side arms can be set in 16-inch intervals, hooking on to the frame ledgers at a point lower than the platform to place tools and materials at a convenient working height. When setting up, keep in mind that the wall surface should be no more than 14 inches from the open, working side of the scaffold. Any farther, and you have to provide guardrails. And remember that side arms should be used to support only personnel, not materials.

Figure 10.

Side arms (top) extend the width of the platform and may be offset from the main platform for working convenience. Frame ledgers provide height adjustment in 16-inch increments.

Also keep loading in mind when designing your scaffold. Light-duty scaffold planks top out at 25 pounds per square foot, medium-duty at 50 pounds per square foot, and heavy-duty at 75 pounds per square foot, applied uniformly over the entire span area. Proprietary planks are rated accordingly. As a rule, plank deflection must not exceed 1/60 of the span when loaded, which equates to 1 3/8 inches over 7 feet.

Water and fungal rot can degrade even approved planking, so we keep our planks dry when they're not in use. We store them indoors in such a way that air can circulate freely around them. We also inspect the planks before every use for any signs of decay or damage. When I find a suspect plank, I don't leave it lying around; I cut it up into scrap.

Guardrails. Work platforms higher than 10 feet above the base level must have two parallel guardrails placed approximately 19 inches and 42 inches above the work platform (Figure 11). Actually, we're even stricter than that: In our company, any staging more than 6 feet above the ground must have a guardrail. Cross braces are not guardrails, so at every working level of a multilevel scaffold, we install proprietary metal railings or 2x4s held in place with #18 tie wire. Around the top platform level, clamp-on tubular steel mounting posts adapt the guard railings.

Don't forget the open platform ends, which also require guardrails.

Figure 11.Work platforms higher than 10 feet above the base level must have two parallel guardrails placed approximately 19 and 42 inches above the work platform to prevent falls (far left). Even platform ends must be closed (left). The full platform and high railings on this slate roofing job supply an unbeatable degree of comfort, convenience, and efficiency.

How Much Is Enough?

If I can't fit the staging I need for a job in my pickup truck, I turn to a scaffolding rental company for the equipment. These outfits deliver and pick up for short money and provide components that are properly stored and inspected for continued use. A rental company can also provide occasional specialty equipment that you don't use often enough to justify purchasing.

Estimating scaffold needs. Although the basic assembly in a frame scaffold system consists of two frames and two cross braces, a 1:1 ratio, the ratio shifts in favor of the cross braces in multiple assemblies, to 1:1.8. That's a good general ratio to apply when calculating scaffolding. Never skimp on bracing.

Sometimes bracing can create a barrier between you and the work surface, or it can't be installed because of a structural obstacle. In such cases, plan to use straddle braces or straddle frames instead, which are specifically designed to provide access and clearance around obstructions (Figure 12). Putlogs — trusslike staging beams used to bridge over projecting obstructions and to keep passageways open below the staged area — must be firmly attached to the staging frame with proprietary hangers or clamps. Putlogs give a frame scaffolding system an enormous amount of adaptability (Figure 13).

Figure 12.

Don't submit to the temptation to remove or simply not install braces on the working side of a scaffold. Instead, use straddle frames, which replace the brace function while still providing good access to the work surface. These walk-through frames allow unimpeded traffic flow beneath the staging.

Figure 13. Putlogs — essentially tubular steel trusses — allow you to scaffold around structural obstacles like this projecting roofline (top left), or to maintain clear passage beneath a work platform (below). Special brackets connect the putlogs to the frame (top right).

Things To Watch For

I have worked as a consultant on a number of lawsuits related to scaffolding tragedies. I've seen nearly everything go wrong that can, including overload failure, a wall that fell on its staging and caused it to fail, faulty erection, component failure due to rust and mishandling, and improper use of staging components.

Remember: When you erect staging, you're not the only one who's going to use it. You have to be aware of traps like poor access, planks without proper overlap, open ends of work platforms, unstable anchoring points, and missing bracing. Work platforms must be completely decked in; they should not consist of just one or two planks (Figure 14). Even where restricted by stair penetrations or obstacles, walkways should never be narrower than 18 inches.

Figure 14.Full planking prevents sideways shifts and treacherous gaps in the platform.

Inspecting components. You never want to use the rusty staging lifted out of the mud and weeds behind your uncle's garage. Advanced corrosion reduces the tube-wall thickness to an unknown and therefore unsafe level of performance. It takes ultrasonic testing to accurately determine whether the wall thickness is compromised, so I keep it simple: If the tubing shows deep pits and flaking rust, I cut it up and say goodbye.

Other things my crew is trained to watch for include cracked or broken welds; broken, missing, or inoperable cross-brace lock devices; splits in the tubing; voids or holes in the tubing from accidental impact, cutting, or abrasion; out-of-round tubing (a forced fit between proprietary frames is a good indicator); bent legs; bent crossmembers; and out-of-square frames (Figure 15).

Don't mix staging frames from different manufacturers unless they fit together without forcing and all connecting points provide an exact match. Tube diameter can vary just enough from one maker to another to prevent common use of the coupler pins. Some tubes are drilled to receive coupler toggle pins at 30 degrees and others at 90 degrees, an obvious and unacceptable mismatch (Figure 16).

Figure 16.Unlike frames must not be combined unless they provide an exact match between coupler and toggle pins, braces, tube diameter, and, most important, structural load ratings. In the photo at right, one maker's walk-through frame is compatibly stacked on the ledger frame of another. Sometimes, though, brace mounting locks are welded to the frame at different spacings from one maker to the next, making the two brands incompatible. In the photo at far right, the wire tying this brace between two unmatched frames is a real no-no.

Furthermore, the vertical spacing between brace locks may not be equal or in the same location from one brand of frame to the next. This makes it difficult or impossible to level the frames and hook up the cross braces.

Most important, the duty rating may not be the same from one make to the next. All manufactured scaffold components must be capable of supporting four times the maximum intended load, but since different frames may have different ratings, the odd frame in the assembly could become a weak link.

Words to the Wise

When it comes to scaffolding, there are no stupid questions and you can't be too careful. So I will close with a few final tips:

Beware of electrical service drops and power lines. Refer to the chart published in OSHA's guide and elsewhere for proper safe clearances for staging and personnel. Your power company will come out and sleeve the lines, usually at no charge.

Start with a good foundation. Check the soil condition: Is it compacted cut or loose fill? In urban work, the sidewalk may be hollow. Don't take a chance by assuming a slab is solid; we use a minimum 2x10 mudsill, 18 to 24 inches long, beneath screw jacks or base plates.

Never use concrete block or wood shipping pallets to build up your base. Concrete block on edge can fold over or be punched through and pallets can collapse.

Always use screw jacks on the base frames to level and plumb scaffolding.

Pull a string line across multiple frame assemblies to establish a common level.

is a masonry contractor in Littleton, Mass. Thanks to Alan Kline of Lynn Ladder & Scaffolding for assisting with this article.