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June 2015

Solid Platforms

By | OSHA Standards & Regulations, Resources, Scaffolding Planks, Scaffolding Platforms | No Comments

It is true that a scaffold without a platform cannot be a scaffold since a scaffold is defined as a “temporary elevated platform and its supporting structure.” It can, therefore, be assumed that a platform is rather important. But it isn’t the OSHA standards, or any other regulations and guidelines that make a scaffold platform important; it is the absolutely critical nature of a platform that makes it imperative that scaffold designers, erectors, and yes, users fully understand what makes a scaffold platform safe for use. So, what makes a platform safe and how is its safety assured prior to placing the platform and its supporting structure to use? Let’s explore those issues through a series of frequently asked scaffold platform questions:

What materials can be used to construct a scaffold platform?
Anything can be used to construct a platform. Common materials included solid sawn wood members, manufactured wood products, aluminum, steel, fiberglass and plastic. In fact, even cardboard and concrete could be used although I doubt the erectors would appreciate installing concrete panels!

If solid sawn lumber is used to construct a platform, does it have to be “Scaffold Grade”?
It depends. Some standards, such as the U.S. Federal OSHA General Industry Standards, 29 CFR 1910, require the use of scaffold grade plank while the U.S. Federal OSHA Construction Industry Standards, 29 CFR 1926, do not. When designing for a construction industry application, if you are a qualified designer who can calculate lumber stresses and control the loads that will be applied to the lumber, then you can specify any wood you desire provided the lumber maintains a safety factor of at least 4 [29 CFR 1926.451(a)(1)]. Having said that, the Scaffold & Access Industry Association, SAIA, the Scaffold, Forming & Shoring Institute, SSFI, and industry professionals encourage the use of scaffold grade plank when using solid sawn lumber.

Do all planks have to extend (overhang) their supports by 6 inches minimum and 12 inches maximum?
No. If the plank is secured from movement so that the individual plank cannot slide off its support, it does not have to extend a minimum 6 inches over its support. Conversely, it can extend further than 12 inches (in some jurisdictions the maximum overhang is 18 inches) if the plank is secured from movement, including uplift. Of course the plank has to be designed so the use of a long overhang doesn’t result in an overstressed plank.

Which jurisdictions allow an 18 inch overhang?
If you are a scaffold designer, erector, inspector or user you should know the answer to this question. If you don’t know, get training for your jurisdiction. For example, federal OSHA allows overhangs up to 18 inches for plank longer than 10 feet, California allows 18 inches for any length plank and the US Army Corps of Engineers limits all plank overhang to 12 inches, regardless of plank length.

I have been told that nailing plank damages them. Can you nail plank together to keep them from moving?
Of course you can—its wood! If you pound in the nail in the same spot for a long time you’ll probably damage the plank but you really have to keep hammering it.

Is it true that you cannot install plywood on top of plank?
No. While at one time US federal OSHA issued a Letter of Interpretation (LOI) that claimed that you could not install plywood on top of plank, it was rescinded (the LOI went away). Keep in mind that once plywood is installed on top of plank, the plank become “joists” just as 2×4’s or 2×10’s (plank standing on edge) would be.

Speaking of joists, what can be used to support a plywood deck?
You can use whatever works. That doesn’t mean slapping down whatever is available—it means anything that works; any structural member that is designed by a qualified person (see US federal OSHA standard 29 CFR 1926.451(a)(6)) can be used. This includes solid sawn lumber, laminated veneer lumber, aluminum joists, steel beams, and tree trunks if you can figure out how strong they are.

Can I use balsa wood?
Sure, as long as it has the sufficient strength.

US federal OSHA specifies that a platform cannot deflect any more than 1/60 of the span when loaded. [29 CFR 1926.451(f)(16)] Does this apply to the typical manufactured plank that is made out of aluminum and has hooks on each end for hooking over its supports?
You it does. However, based on my experience, if your 10’-0” aluminum platform unit deflects 2 inches due to the load, you may have a serious overload problem.

A common practice is to install a “skip plank” platform where the plank are spaced at about 19 inches on center, resulting in a platform where every other plank is removed. This of course is covered with plywood and requires only half the plank to construct the platform. It has been claimed that a skip plank platform is as strong as a fully decked platform, especially because it seems to not deflect as much. Is this true?
How can it be as strong if it has half the plank? It just seems that way because the plywood helps to distribute the load to more than one plank, making it feel stronger. Don’t fool yourself—it is half as strong. Actually it is less than half as strong since the plank have to support the plywood.

You have mentioned plywood several times now. What thickness plywood is needed for a scaffold platform?
I cannot answer that. It all depends on the members supporting the plywood and the spacing of those members. Remember, and this is important, just because the plank supporting the plywood span 10 feet, doesn’t mean it is a “light duty scaffold.” Your platform must be designed by a qualified person, a person who knows how to calculate loads, use charts accurately and/or have the ability to “solve the problem.”

Can particleboard, oriented strand board (OSB) or flake board be used as a platform?
Sure. See the answer above about designing platforms.

Is there such a thing as an “OSHA approved plank”?
Nope. OSHA doesn’t approve any product. It is up to you to use the plank properly. If you don’t know how to do that, get some training.

Suspended Scaffold Q & A

By | Resources, Scaffolding | No Comments

A suspended scaffold is a marvelous tool for workers to utilize to gain access to work locations that would be difficult if not impossible to otherwise reach. Unfortunately, the general perception is that suspended scaffolds, particularly two point suspended scaffolds such as window washers two point suspended scaffolds, are inherently dangerous and those individuals who use them are similarly inherently dangerous. This is due in no small part to the media exposure that suspended scaffold failures receive. The reality indicates otherwise. Perhaps these questions and answers will help mitigate the fear of suspended scaffolds.

What is a suspended scaffold? A suspended scaffold is a temporary platform that is supported by non-rigid means such as cables, chains or ropes. It is not to be confused with supported scaffolds which are temporary platforms that are supported by rigid means such as legs, posts or frames.

Is a suspended scaffold the same as a hanging scaffold? No. A hanging scaffold is a “temporary work platform without support from below, secured to an overhead structure using fixed length rigid suspension members” while a suspended scaffold utilizes non-rigid suspension members.

In addition to a guardrail system, are users of all suspended scaffolds required to wear personal fall protection equipment? No. A user of a single point or two point suspended scaffold, that is a platform suspended from either one rope or two ropes, must wear personal fall protection equipment properly connected to a lifeline. The reason for this requirement when using a single point suspended scaffold is obvious: if the rope breaks, you are in big trouble if you aren’t wearing a harness connected to a lifeline and anchor. On a two point suspended scaffold, typically only one line breaks, leaving the platform hanging vertically (and making really cool photos for the media) with one worker dangling from his lifeline while the other worker is desperately clinging to the other suspension rope.

Are you telling me that workers utilizing a temporary platform that is supported by four suspension wire ropes don’t have to wear harnesses secured to an adequate anchor?According to most regulations, yes.

That doesn’t sound right—are you messing with me? Nope.

Why doesn’t a multi-point suspended scaffold user have to wear a harness attached to an adequate anchoring system? It is assumed that the platform is sufficiently rigid so that if one suspension rope fails, the platform will remain more or less level and the workers will not slide/fall off the platform. Of course, if your platform lacks the necessary rigidity, you should be utilizing personal fall protection. For example, if you are suspended by three ropes, you probably need to utilize personal fall protection for the unlikely event that you will lose one of your suspenders. On the other hand, if you are on a rigid platform suspended by many suspension lines, such as a suspended platform under a bridge, personal fall protection is probably not warranted. Of course, you must always comply with the qualified scaffold designer’s instructions.

Why do single and two point suspension scaffolds seem to frequently fail? They don’t. If you look at how many suspended scaffolds are used daily in North America, you will find that the failures are insignificant. It’s just that the media likes to report them, You Tube likes to show them and people like to talk about them! (Of course, if you are the worker who experiences a failure, it probably won’t seem insignificant to you.)

Does a cantilever beam used to support the rope that supports an elevated suspended temporary platform have to be designed by a Professional Engineer? Maybe and maybe not.

When is a Professional Engineer required? First of all, the Professional Engineer has to be qualified. That qualified Professional Engineer is required for all multi-point masons suspended scaffolds where the cantilever beams used to support the ropes are secured to the floor. Usually a qualified Professional Engineer is required to design the cantilever beam and rigging, particularly if it is purpose designed for a specific situation. Also keep in mind that many agencies, such as Departments of Transportation, require a qualified Professional Engineer be involved.

Are suspended scaffold erectors required to utilize (wear) personal fall protection equipment? Erectors are expected to utilize personal fall protection equipment when they are exposed to a fall hazard, such as when they are installing rigging on a roof or open sided floor.

Do suspended scaffold users have to have a license/permit to operate a suspended scaffold? Perhaps; it depends on the jurisdiction. Large cities, some counties and state governments require licensing and/or permitting. Before starting any scaffold project, it would be wise to determine the necessary regulatory requirements.

Is a temporary suspended scaffold the same as a permanent suspended scaffold? No. Temporary suspended scaffolds must comply with a different set of regulations and standards than a permanent installation, known as a “PI.” As the names suggest, a temporary suspended scaffold is commonly used in the construction of new structures and intermittent maintenance while a PI is specifically designed for a building, installed permanently on that building, and is intended to be used for providing routine maintenance and renovation.

What appears to be the most common cause of suspended scaffold failures and why? The most apparent cause is lack of training. There are so many safety devices incorporated into temporary suspended scaffold equipment, such as overspeed brakes and extremely high safety factors that it requires ignorance and possibly purposeful stupidity to make them fail.

What is the most important aspect of suspended scaffold utilization?  Training.

Where can I get that training? One good source is the Scaffold & Access Industry Association.