Scaffolding Platforms

Plank Criteria

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There are two criteria that predict the safety of a scaffold platform.  One of the criteria involves the engineering properties of the scaffold unit.  The other criterion addresses the correct installation of the platform.  Correct installation includes proper support, correct positioning to limit spaces between platform units, and the minimum width of the platform.

The Federal Occupational Safety and Health Administration, OSHA, and other agencies, set forth the minimum standards for the installation and use of platform units.  For example, regulations address the minimum and maximum overhang of platform units, the allowable deflection, the space between units, and the distance from the edge of the platform to the work surface and the guardrail system.  These regulations are in the subsection on platforms, 29CFR1926.451(b), and are quite specific.  The regulations address all platforms, including solid sawn wood plank, laminated veneer lumber (lvl), metal fabricated decks, and platforms constructed of structural members and sheathing such as plywood.  These specific regulations ensure that the platform you construct will stay on the scaffold, will be large enough so you won’t fall off the platform, and won’t have any openings that you may fall through.

Engineering properties also predict the safety of the platform.  For manufactured platforms, such as aluminum decks and laminated veneer lumber, the manufacturer indicates the capacity of the product.  For solid sawn plank, determining the capacity is not as straightforward due to varying factors.  These factors include the dimensions of the plank, the specie of tree, what part of the tree is being used, and if the wood has any damage.  How in the world do you determine if the plank is strong enough?  Fortunately, you have help!  Qualified engineers can determine the strength of the plank you are using if the dimensions, the specie of tree, and the quality of the wood are known.  The engineer will also need to know the span of the plank, that is, the distance between supports.  While you can give the engineer the dimensions and span of the plank, the type and quality of the wood is another story.  Unless you cut the tree down yourself, you probably won’t be able to tell if the wood is pine or poplar.  And unless you have learned how to grade lumber, you won’t know if the wood is any good.

How, then, is the grade of the wood determined?  Qualified, trained lumber graders are one method used by lumber mills to determine the strength of wood.  These individuals are trained to determine the various strengths of wood that will come from a tree.  Factors used to determine strength include such things as density (how many rings per inch), the straightness of the grain, and the frequency of knots.  Straighter grain, higher density, and fewer knots will result in a strong piece of wood.  On the other hand, frequent knots and low density will result in a low strength piece of wood.

The engineer relies on the ability of the grader to do his or her job correctly.  The engineer also relies on the accuracy of the stamp to determine precise information for you to use.  The bottom line here is that the information in the grade stamp dictates the accuracy of the engineer’s calculations.  Of course, this information will only be accurate if the plank you use has been graded by a qualified grader, using recognized standards.  If the wood is not as good as the grade stamp indicates disaster will surely follow.

For typical situations, it is recommended that only Scaffold Grade plank be used since this will enhance safety on your scaffold project.  Scaffold Grade plank is a very specific grade of lumber that has a very high strength compared to other commonly found lumber on a construction project.  However, if you choose to use a plank other than scaffold grade, it must be engineered for proper use.  This is the only way you will be safe and in compliance with the regulations.

Do not take chances with solid sawn wood plank.  A grade stamp from a recognized grading agency is your guarantee of accuracy.  High strength lumber is not cheap.  Neither is a worker’s life.  If the board breaks, there is no back-up.

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.

Why They Work: Engineering Principles of Aerial Work Platforms

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Aerial Work Platforms (AWP) are wonderful machines. They provide quick elevated access for workers to perform their tasks. They are mobile and safe to use. But how do they work? Why don’t they fall over? Well, they do fall over but it isn’t the machine’s fault—it’s the guy who forgot his training and screwed up.

Aerial Work Platforms encompass the various machines that are addressed in the 92 series of standards promulgated by the American National Standards Institute (ANSI). For example, these standards include Boom Supported Elevating Work Platforms (Boom Lifts), Self-Propelled Elevating Work Platforms (Scissors Lifts), Vehicle-Mounted Bridge Inspection and Maintenance Devices and Mast Climbers. Although the ANSI 92 series standards also address other machines, this article will focus on the engineering magic of boom lifts, scissors lifts, and mast climbers.

Mast Climber

Mast Climber


Scissors Lift

Scissors Lift


Boom lift

Boom Lift


While each of these three machines provides a platform that elevates, each machine does it best for specific conditions. For example, while a boom lift can provide access to the same locations as a scissors lift, a scissors lift typically can provide a larger platform. A scissors lift can provide access similar to a mast climber but a mast climber can support heavier loads and take the platform to a much higher elevation. However, in spite of these variations, the underlying engineering principles are the same.

Issues to Consider

When it comes to AWPs, the designer needs to address specific issues unique to the machine that is being designed while also addressing issues common to all machines. The most obvious issue is the strength of the machine. Each machine must be designed to support a certain load if it is expected to be functional. This load could be limited to one worker or it could be maximized to support heavy material loads such as pallets of brick or block. Typically steel is used as the material of choice for the load bearing elements, augmented by other materials chosen by the designer based on weight, economics, esthetics and suitability.

Stability is as important as strength. After all, what good is the elevated platform if it continues to fall over when you use it? In fact, the engineering property called the “center of gravity” should be of great concern to the designer as well as the user. Any AWP will do well provided the Center of Gravity (CofG) stays within the confines of the base of the machine. Once the CofG moves outside the base of the machine the operator will have a rather disconcerting experience if not a deadly one.

The CofG and its location are determined by the weight of the machine and the loads placed on the machine. As an illustration, picture a cube of concrete, or Styrofoam® (if you want to be a lightweight) that is 24 inches wide by 24 inches long by 24 inches high. The CofG is exactly in the center of the cube, 12 inches from each side. Now, place a six-pack of your favorite beverage on one edge of the cube. The CofG will shift towards the side of the cube where the six-pack is. Place it on the corner and the CofG will shift towards the corner. It will not shift all the way to the corner since the weight of the concrete is much greater than the six-pack, especially if you drank part of it! Now, since you drank all of the six-pack, place a twelve-pack at the opposite corner and the CofG will shift back past the center and towards the twelve-pack corner. The same phenomenon occurs in AWPs. For a scissors lift, the CofG easily stays within the wheelbase since the platform is never much bigger than the wheel base. However, for scissors lifts which have a cantilever platform, the CofG will shift towards the cantilever but will not move out of the wheelbase unless of course you stock the cantilever with enough six-packs to shift the CofG outside the wheelbase; now you have a problem – you just spilled your favorite beverage.

What about a boom lift where the basket is far from the wheelbase of the machine? Well, the CofG is still within the wheelbase because the designer made sure that no matter where you move the boom the CofG will never leave the wheelbase. Of course, should you overload the basket (that is loading it beyond the allowable load specified by the designer) or override the safety features that limit the boom extension, you will destabilize the boom resulting in some rather nasty results.

Mast Climbers operate under the same engineering restrictions but have another element that must be controlled. Since the platform is supported by a mast, the CofG must remain within the mast base. Because the mast base is typically rather small, like 2 feet by 2 feet, the mast must be supported at specific intervals to maintain the mast in plumb. Additionally, the platform loads must be carefully and continuously monitored to ensure the loads are balanced. That explains why there are loading charts on Mast Climber platforms.

Speaking of loads, boom lifts, mast climbers and scissors lifts must never be overloaded since the strength of the machine is based on the expected loads and the stability of the machine is based on the expected loads and use of the machine. Remember that overload does not mean collapse; it means that there is a safe load limit and anything above that will cause the machine to malfunction, stop working, fall over or fall down. None of these outcomes is healthy—believe what the manufacturer and the ANSI standards tell you!

Plank or Platform?

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Is it a plank or is it a platform?  Can a plank be a platform or can a platform be a plank?  When it comes to the working surface for a scaffold, these questions are common.  But they shouldn’t be.  It appears the confusion arises because the use of wood planks for scaffold platforms is commonplace.  Simply stated, wood planks can be used as a platform.  Therefore, wood planks can be a platform but a platform is much more than just wood planks.  To understand this, it is good to know that typical scaffold standards address two issues with scaffold platforms.  The first is the strength of the platform and the second is the construction of the platform.

A scaffold platform can be constructed from any material provided that the material has sufficient strength to support four times the load that will be put on it.  This ratio of four is the safety factor.  For example, if you want to put 1,000 pounds on your scaffold platform, your platform has to support 4,000 pounds.  That’s pretty simple assuming you know how strong the platform is and you also know the weight of the workers and materials you will be placing on the platform.  If you don’t know these two things, then you cannot determine if the platform is overloaded and consequently you will be in violation of the standard that requires a 4 to 1 safety factor.  I cannot help you with the load you are placing on the platform; it is impolite to ask people how much they weigh.  However, depending on what material you are using for the platform, I may be able to help with how much the platform can support.

If you choose Styrofoam for your platform you are out of luck—I don’t know the strength of Styrofoam.  If you choose a fabricated plank, like an aluminum hook plank or a laminated veneer lumber (lvl) plank, the manufacturer can tell you how strong their product is.  Of course, if you don’t know who the manufacturer is or the manufacturer hasn’t tested their product to determine the strength, you are once again, out of luck.  However, if you decide to use a solid sawn Southern Yellow Pine scaffold grade plank, for example, you are in luck!  I can provide you with a chart that shows the capacity.  Keep in mind that the U.S. federal OSHA standards do not require the use of Scaffold Grade plank but if you do not know how to calculate the strength of the plank you are using, you will have a very difficult time convincing anyone that you have a sufficient safety factor.  That’s why it is prudent to use a scaffold grade plank when using solid sawn lumber for your scaffold platform.

The second issue, the construction of the platform, is cleverly addressed in some standards by referring to the components of the platform as “platform units.”  While this is technically correct, it is reasonable to assume that the standard is talking about 2×10 wood planks.  Minimum standards require that scaffold users are provided with a platform that is safe, for example a platform which won’t become misplaced and dump the occupant to the level below.  The standards also want to eliminate hidden surprises such as cantilevered platforms that are inherently unstable, exposing the user to a potentially untimely demise.  The standards will normally specify the minimum overhang and maximum overhang for planks (platform units), the space between planks, and the distance not only from the work surface to the platform edge but also the maximum gap between the back edge of the platform and the guardrail system (assuming one is being utilized).  The bottom line to all this is to ensure that the scaffold has a safe, stable and complete platform.

The platform does not have to be 2×10 wood scaffold planks.  It actually can be Styrofoam.  It can be aluminum joists and plywood.  If you choose to use joists and plywood, how do the standards apply?  How do you take a standard that requires that “platform units” overhang their supports at least 6 inches and no more than 18 inches and apply it to a 4×4?  The answer is straightforward if one understands the intent of the platform standards:  If the platform is stable, it is safe.

While all this could be straightforward the reality is quite different.  There is no single set of standards.  Various governmental agencies have established their own specifications and they do not necessarily agree from one agency to the next.  For example, US federal OSHA specifies that the maximum overhang for a 12’-0” long “platform unit” is 18 inches, while the Army Corps of Engineers allows only 12 inches.  Go figure.  In California, the overhang can be as much as 18 inches, no matter what the length of the plank is.  Go figure.  Is there an explanation for these contradictory requirements?  I suppose there is but I am not aware of it.  I do know that varying requirements do not make it easy for scaffold erectors.

Is it a platform or is it a plank?  Or is it a platform unit?  12 or 18 inches?  What if it is 12 and a half inches when it should be 12?  Do you know the answer?

Are Scaffolds That Dangerous?

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

A clarification of the role that wood scaffold plank in the construction of a scaffold platform.

When I tell someone that I work in the construction industry and I design scaffolding, the response is interesting.  If its fellow engineers, they think I’m nuts for working in such a dangerous field.  The liability must be incredibly high.  If I tell a safety person, sympathy is extended due to an obviously difficult career choice.  Tell an accountant and I’m asked how I ever make any money.  Fortunately my mother had always thought it kind of exciting.

But really, can such an activity like scaffolding erection and use be exciting?  Especially since so many people think it is so dangerous?  I can only speak for myself but it is my opinion that it isn’t dangerous and yes, it can be exciting, especially when there is a challenge for access that must be resolved.  Not dangerous you ask?  That’s right; in the overall scheme of life scaffolding is no more dangerous than a lot of other activities.  It’s just that scaffolding appears to be dangerous.  And besides, it’s easy to spot certain deficiencies in an erected scaffold.  You don’t have to be an expert to notice a missing guardrail on a supported scaffold. And you don’t need a doctorate in engineering to ascertain the lack of access.

OSHA consistently issues enough citations to employers each year for scaffold violations that the product of our efforts appears on the Top Ten list year in and year out.  It’s no wonder that the populace thinks we’re crazy with a track record like that.  Is there something sinister going on—perhaps a diabolical industry wide plot to perpetuate the perception of danger in the business of providing access to workers?   I hope not!  Let’s take a look at how the system works.

Scaffolding is a highly regulated business.  Besides federal OSHA standards that dictate minimum behavior, states and even local jurisdictions have regulations that specify how scaffolds are to be erected.  To be sure, the federal OSHA standards are performance standards meaning that the employer and employer have some leeway in achieving compliance with the standards. But that leeway comes with a price.  And herein lies the first problem.  The price for the opportunity to have some flexibility in complying with performance standards is the requirement that the scaffold erector and user must have knowledge about the hazard and the available options to mitigate that hazard.  This also means that the erector must know about the hazard and the applicable regulations in the first place.  In other words, if you want to dance you better know the song.

This brings us to the next problem which is the requirement that erectors, users, evaluators (site safety manager) and compliance officers have an understanding of the intent of the standards.  In fact this may be the biggest problem.  Nobody knows what’s going on!  The erector hasn’t been properly trained and consequently either believes anything a compliance officer tells him or thinks she knows everything.  In any event, everybody starts making up stuff because they don’t know any better.  The compliance officer, on the defensive because he hasn’t been provided adequate training in the subject matter, uses intimidation to make the point.  If that doesn’t work, then threats always seem to win the day.

The next problem is founded in ignorance.  When an individual doesn’t know any better, common sense, openness, a desire to learn and an open mind disappear.  Its replacement is an irrational desire to “win,” no matter the cost.  What a system.

So, how does all this result in scaffolding consistently showing up on OSHA’s Top Ten?  It’s simple: scaffolding is an easy target and we perceive that it is killing people all the time.  Furthermore, it’s an easy citation to write.  Drive down the street, look at a construction project and what do you see?  Yep, it’s a scaffold.  What do you see missing?  Yep, it’s the guardrail.  That’s an easy citation to write.  Let’s see what else I can find.  I remember a regulation that says erectors have to have fall protection and those guys putting up the scaffold aren’t tied off.  I don’t know much about fall protection and I can’t remember the criteria for a correct personal fall protection system but I’ll cite them anyway.  The erectors probably don’t know anything about it either.  That’s an easy citation to write.  Of course, while I’m staring at the scaffold as I drive by, I’m not paying attention to my driving and rear end the car in front of me, injuring the child who isn’t in a child seat or strapped in.  But that’s okay; we accept killing thousands of motorists and injuring many more thousands.  But heaven help the erector who isn’t “tied off.”  I can tell he’s dangerous and the scaffold he is working on is dangerous too.  How can the scaffold not be dangerous?  Just look at all those citations each year.

If we focused on the real hazards on a jobsite instead of the easy fixes, the jobsite would be a much better place.  If we actually trained the compliance officers to the real hazards, the Top Ten would look a lot different.  If we actually trained scaffold users to the real hazards, the Top Ten would look a lot different.  But that takes too much work.  It’s a lot easier to dumb it down.  Of course, the result of that approach is that too many people think scaffolds are dangerous.  And of course, that’s really dumb to think that.

Industrial Scaffolds – Unique or Common?

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Scaffolds used in locations such as refineries, chemical plants and power stations are often referred to as industrial scaffolds, suggesting they are unique to that environment.  But are they?  Is there something mysterious going on in the refinery that transposes a common scaffold into a magical load bearing wonder that supports workers at heights?  Or is that scaffold just a regular common scaffold similar to a commercial or residential scaffold?

I believe the answer is somewhere in between.  Well, that stuff about a scaffold being transposed is a bit of a reach (no pun intended) but one significant difference between industrial and other scaffolds is that the industrial environment produces scaffold work habits not often seen in the commercial sector.  One conspicuous example is scaffold inspection.  US Federal OSHA requires that scaffolds used in construction be inspected before each workshift by a competent person [29 CFR 1926.451(f)(3)].  In the industrial environment this requirement is taken seriously.  Frequently the inspection task will be assigned to one company although multiple employers may be using the scaffold during that workshift.  More often than not, the scaffold company that erected the scaffold will have that duty.  Of course, this doesn’t mean the scaffold users don’t have to know anything about scaffolds nor does it relieve them of the obligation to use a safe scaffold.  After all, the OSHA standards involve all of us [29 CFR 1926.454].  Once the scaffold is inspected at the beginning of the workshift (notice that it isn’t each day; it’s before each workshift) [29 CFR 1926.451(f)(3)] a record may be made of the inspection.  This record may be a simple tag or it may be as complex as a written record that is retained for the duration of the project.  In conjunction with this method of inspection is the absolute rule that no one modifies, changes, dismantles or messes with the scaffold other than the workers assigned the task of scaffold assembly [29 CFR 1926.451(f)(7)].  Frankly, this is why the sole source inspection and tagging system works in the industrial environment; nobody messes with the scaffold.

Unfortunately, the same cannot be said about the commercial or residential environment.  In fact, most workers on commercial job sites, based on my experience, consider themselves experts in the design and erection of scaffolding and therefore can do whatever they want with the scaffold.  Even when the general contractor attempts to implement the controls seen in a refinery, the controls are typically circumvented by those who have the least knowledge and are consequently most exposed to injuries and death due to unauthorized modification of the scaffold.

Another example of the unique environment found in industrial scaffolds can be seen in the complexity of the constructed scaffolds.  Because of piping, structural elements, electrical lines and other obstructions it takes considerable skill to erect a scaffold in a refinery or power plant.  (Now, before you professional commercial scaffold erectors get mad at me, I’m not suggesting that professional commercial scaffold erectors are not qualified.)  Those charged with industrial scaffold erections typically comply with the OSHA standard that specifies that scaffolds shall be erected by “trained and experienced” workers [29 CFR 1926.451(f)(7)].  Such may not be the case in commercial construction where the painter, who knows how to paint, may know very little about scaffolding but erects the scaffold anyway.  In that case, the scaffold is erected for the convenience of the painter and may not work for the glazer.  Industrial scaffolds, on the other hand, are often erected for all the trades to use or, if that is not possible, the scaffold is dismantled and re-erected.

Environmental controls appear to be more restrictive in industrial applications as well they should be.  However, lessons from the power plant could be learned in the commercial project where we still fight resistance to eye protection, hearing protection and other equipment meant to protect the worker.  As for the residential market, some days it seems hopeless to expect anything.

Fall protection is another aspect of the industrial market that is not as readily appreciated in the commercial or residential market.  It is not uncommon at a chemical plant to not only expect workers to work on fully guardrailed platforms but to utilize personal fall protection equipment and tie off when they get to their work station.  While this is a trend among large general contractors in the commercial construction market, the practice is considerably behind the industrial market in implementation.  And again, when it comes to the residential market, personal fall arrest equipment usage is rarely observed.  (Of course, I’m not endorsing the concept of both guardrailsand personal fall arrest equipment since it is really rather redundant; I’m just describing my observations.)

How about scaffold platforms?  This is interesting since industrial scaffold platforms typically have more obstructions and penetrations than a commercial scaffold will ever see.  While steel plank are more common in industrial scaffolds and plywood is commonly used to cover gaps since the gaps are less tolerated than in commercial installations, it is not uncommon to notch wood plank so it will fit around an obtrusive pipe or conduit.  Commercial scaffolds usually have a clear platform that is easier to erect and use.

Finally, access in the industrial environment is usually more difficult than in the commercial scaffold application.  Attachable/clamp-on ladders are the access of choice for small platforms and limited use in the refinery or power plant since they are easier to install around obstructions.  Of course, where access for a large number of workers is needed, a systems scaffold stairway is commonly used.  Commercial scaffolds will utilize stairs and ladders but also will utilize frame scaffolds and the access these frames provide.  In residential applications access is anybody’s guess and a ladder sighting at a house is a pleasant surprise.

The bottom line however, is that the industrial scaffold serves the same purpose as a commercial or residential scaffold in that it provides a safe temporary elevated platform to support workers or materials or both.  Where the scaffold is erected and used matters not—it still has to be erected and used correctly.

Suspended Scaffold Mysteries

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My experience indicates that people easily get confused about suspended scaffolds.  I’m not sure why that is other than it may have something to do with their knowledge, or lack thereof, of suspended scaffolds and how they work.  This shouldn’t be surprising since most people base their knowledge on what they have seen on the evening news.  Here are a few questions that occur about suspended scaffolds:

What is a suspended scaffold?  This is a fundamental question that has an easy answer.  A suspended scaffold is any temporary elevated platform that is supported by a non-rigid means, such as by rope or chain.  For example, if you have a platform hanging by your mother’s clothesline, it is a suspended scaffold.

Do all suspended scaffold platforms have to be supported by wire ropes?  No.  You can use anything you want as long as the support is strong enough.  This can be clothesline (see answer above), wire rope, cable, manila rope, chain, string, duct tape, bungee cords or rubber bands.  As long as it has the required strength, and you can prove it, you can use it.

What is the required strength of wire ropes?  It depends on what you are trying to hold up.  For temporary suspended scaffolds used in construction and general industry, the safety factor must be at least 6; that is, the suspension line must be 6 times stronger than the load you are placing on it.

Can I really use duct tape?  Well, if you can prove that it will hold 6 times the load you put on it, then you can use it.  I have no idea how you would prove that so I strongly recommend against using it, even if it is “professional grade” duct tape!

Is there a difference between temporary suspended scaffolds and the scaffolds that commonly called “permanent installations”?  Yes there are considerable differences.  Different regulations and standards apply.  For example, temporary suspended scaffolds used in construction in the United States must comply with the applicable OSHA construction standards [29 CFR 1926].  A Permanent Installation, (also known as a “P.I.”), must comply with OSHA standards that specifically address P.I.’s.  The significant differences are in the areas of safety factors and fall protection requirements.

I have a 5/16” wire rope but do not know anything about it.  Are all wire ropes of the same diameter the same?  Absolutely not; wire rope strength varies based on the tensile strength of the steel used.  Therefore you must have the data on the wire rope to determine its strength.

Why are wire ropes twisted?  They aren’t twisted but rather are “laid” into strands.  The strands make up the wire rope.  There are a variety of “lays,” such as the Regular Lay and the Lang Lay.  Different lays have different handling characteristics which means that you should select the wire rope with correct lay for the job.

The safety factor for temporary suspended scaffolds used in construction is 4.  Does this also apply to the suspension rope?  No.  The minimum safety factor for the suspension rope is 6.

Why are suspended scaffolds so dangerous?  They aren’t. If you utilize properly designed and maintained equipment, erect the scaffold correctly, and use it correctly, it’s no less safe than any other construction or maintenance activity.

I saw a worker on a suspended scaffold not connected to a vertical lifeline.  Is this legal?  Who cares if it is legal—is the worker safe?  Typically, a worker on a single or two point temporary suspended scaffold is required to utilize both a guardrail system and personal fall protection equipment.  However, on some temporary 2 point scaffolds the personal fall protection system may be built into the scaffold and rigging.  Depending on the design of Permanent Installations, vertical lifelines may not be required due to its design.  Obviously, before you use a suspended scaffold you must know what the fall protection requirements are.

Can I ride on a suspended scaffold without knowing how to operate it?  Yes you can.

What do I need to do to be safe on suspended scaffolds, whether or not they are permanent or temporary installations?  You need training in the specific type of equipment you are using.

Where can I get training on how to use and operate suspended scaffolds?   Well, that should be evident if you are reading this magazine!  The Scaffold Industry Association.

Twisted Confusion

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

It appears the U.S. Federal Occupational Safety and Health Administration, OSHA, has managed to thoroughly twist a well written scaffold regulation to the point where many scaffold erectors, users and compliance officers will be totally confused.  I am referring to a recent Letter of Interpretation that addresses the stability of scaffolds, and more specifically the method for tying a supported scaffold to an adjacent structure so the scaffold doesn’t fall over.

U.S. Federal OSHA periodically issues Letters of Interpretation in response to inquiries from concerned citizens.  Typically, the letter addresses a question the writer may have regarding a specific regulation (standard).  The question normally involves a particular circumstance that may not be directly addressed by the applicable standard.  OSHA responds with its’ interpretation of what OSHA thinks the standard requires.  It is important to understand that a Letter of Interpretation is exactly that, an interpretation by the agency, and is not a change in the standard or its’ applicability.  OSHA cannot change the standard except through the rule making process.  However, the letters OSHA issues do influence the standard of care that one might use for a specific instance.  As with other industries, the impact these letters can have on scaffold matters can be substantial.   Such is the case with a Letter of Interpretation issued by OSHA on March 26, 2010 which addresses the use of #9 wire to tie a scaffold to an adjacent structure for stability.

The questioner asked:  “Do OSHA’s standards permit an employer to double wrap #9 gage steel wire in order to guy, tie or brace a scaffold?”  OSHA’s answer is nothing short of amazing since the scaffold standards, as rewritten in November, 1996, are performance standards as opposed to the original specification standards.  This means that the existing standards allow reasonable options to achieve the result prescribed in the standard.  For example, access is required for all scaffold platforms.  There are a number of options available to the scaffold designer.   Another example, and the focus of this article, is the requirement that all supported scaffolds shall be stable and not fall over.  This can be accomplished by making the scaffold base big enough so it won’t fall over, tying it to an adjacent adequate structure, or guying it.  If you choose to tie the scaffold to the adjacent structure, OSHA prescribes the maximum vertical and horizontal spacing, which happens to be 30 feet horizontally and no more than 26 feet vertically (and less depending on the scaffold width).  Other than that, the tie design is the responsibility of the Qualified Person who designs the scaffold.  The standard, as written, does not tell the scaffolder what to use for the tie, does not tell the scaffolder how much load is on the tie, and does not provide design criteria.  This is not an oversight in the standards; this standard is a minimum requirement and therefore does not, and should not, provide design criteria.  In fact, it would be impossible to provide design data since the circumstances for each scaffold are unique.  Furthermore, the scaffold standards are not instructions.  If you don’t know how to determine the tie load for your scaffold you better get a qualified designer to help you.  This Letter of Interpretation is not the answer.  Here is why.

The letter correctly points out that the referenced section, 29 CFR 1926.451(c), does not “specify whether #9 gage wire is a permissible method of compliance.”  This isn’t surprising since there are unlimited devices and materials that can be used as a scaffold tie.  Unfortunately, from here the letter takes a decidedly wrong turn in that it describes 4 conditions (the letter incorrectly states 5 conditions) that must be met in order for the scaffold to comply with 29 CFR 1926.451(a)(1), which is the standard that specifies that a scaffold and its’ components must have a 4 to 1 safety factor.  Therein lies the problem since OSHA never specifies what load it is using to establish the 4 conditions.  Instead, OSHA dangerously requires that:

  1.  “The #9 wire shall have a minimum tensile strength of 40,000 psi.”  This is a useless requirement, since no loads are specified.  You could use duct tape for a tie if you could show that it is strong enough.  (In theory, OSHA has to prove it would not work!)  And how do you determine the wire tensile strength in the field?  Furthermore, if I use wire with lower tensile strength, is it wrong?  (See #2)
  2. “The #9 wire shall be in a U-loop form (i.e. double-wrapped) around the pole and both wires shall be tied to an eye bolt, which is attached to a masonry wall.  At the eye bolts, both wires shall be twisted to a minimum 5 wraps to get the ultimate strength.”  This is unbelievable!  The requirement “At the eye bolts, both wires shall be twisted a minimum of 5 wraps to get the ultimate strength,” gives the impression that more twists are better, when in reality more twisting will weaken the wire.  What size eye-bolt?  Is it an open 3/8” eyebolt from Home Depot (Capacity = 160 pounds) or a forged eyebolt?  Is this eyebolt screwed into the mortar or should an anchor be used?  What strength is the anchor?  What happens if the wall isn’t braced?  Will it fall over?  How do you count those wraps on the tie?  Is 4 wraps no good?  And will it be stronger if I use 6 wraps?  Furthermore, there is a footnote attached to this requirement that refers to an earlier Letter of Interpretation that declared that single wrapped #9 wire was no good.  That letter was wrong when it was issued years ago and is still wrong; unfortunately OSHA still thinks it is correct.  What about the height or location or shape or size of the scaffold?  Is the load on the tie at the top of a scaffold 300 feet tall the same as the tie load on one that is 30 feet tall?
  3. “Scaffolds shall not be covered with a tarp or any plastic material.”  Does this suggest that if I enclose the scaffold in plywood or screening I will be okay?  I know the answer to that is no but it is sure misleading because it suggests that all open scaffolds are the same.  Is a 3 tier scaffold in a building basement the same as a 3 tier scaffold on top of a cat cracker in a refinery?  I think not!
  4. “A 2×4 timber, putlog or scaffold member shall be placed securely between the masonry wall and the scaffold to protect the scaffold from tipping due to compressive loads.”  What bending stress timber would that be?  Does length have anything to do with it?  Instead of the 2×4 can I use a scaffold tube and screwjack or must it be a 2×4 when wire is used as the tension tie?  Since I’m being told how many wraps on my wire perhaps I should be told how many nails in my “securely placed” 2×4.

Come on OHSA, what were you thinking?  This is embarrassing not only for you but also for all of us in the industry.  The Scaffold Industry Association, SIA, has an alliance with OSHA where we work on issues.  We are here; where were you when this question was raised?  Believe it or not, there are members of the SIA who really do understand scaffolds and are concerned about the correct way to install and use scaffolds.  Having an enforcement agency publish a letter like this is an insult to qualified scaffold designers and a disservice to the individual who asked the question.  The answer to the original question is really quite simple and is found in 29 CFR 1926.451(a)(6):  “Scaffolds shall be designed by a qualified person and shall be constructed and loaded in accordance with that design.”  Let the qualified person decide how to connect the scaffold to the wall.  This is how we address the variables in tie design.  Unfortunately, this OSHA letter dangerously misleads the uninformed worker, and the compliance officers, to think that #9 wire can always be used as long as it has 5 wraps.  This is a dangerous precedent that could ultimately destroy the concept of performance standards.

Simply put, if you cannot design scaffold ties, if you don’t want to learn how to design scaffold ties, and you don’t want to have a qualified person design your scaffold ties, you shouldn’t be in the scaffold business.  And that is not my opinion—the OSHA standards specify it.  No interpretation is required to understand.

Fact or Fiction

By | Fall Protection, Guardrail, Resources, Safety Hazards, Scaffolding, Scaffolding Platforms | No Comments

Fall protection is a huge topic these days what with people falling down and falling from heights.  And since scaffolds are, by definition “any temporary elevated platform,” the issue of fall protection is significant, especially since most scaffold fatalities are due to falls from heights.  It doesn’t have to be this way.  Scaffold suppliers have this really cool product called a guardrail that when used properly, will keep you from falling.  And if you don’t like that, you can always use other stuff to keep from falling to your death.

As you may already know, there are basically two choices when addressing fall protection from scaffold platforms: a guardrail system and personal fall arrest systems.  While not specifically addressed in many safety standards, fall restraint can also be used as a form of fall protection.  Other options are available for fall protection from places like open sided floors and roofs, options that include safety nets, monitoring systems, warning lines and fall protection plans.  It should be noted that lots of safety folks don’t like some of those options since they require workers to behave and we all know that doesn’t always happen.

Experience has indicated to me that when it comes to fall protection, everybody is an expert.  I’m not sure if that is because people fall, making them instant experts, or they think it’s no big deal to “tie off.”  So let’s look at some of these issues and sort out the fact from the fiction.

  1.  Fall protection is required when you are more than 6 feet above the level below.  Fact and fiction!  It depends on the applicable code.  Codes require fall protection at heights ranging from 4 feet to 30 feet.  So find out what the rule is where you are working (or hanging around).
  2. Most workers on construction sites, both commercial and industrial, often use personal fall protection equipment.  Fiction.  Very few workers use personal fall protection equipment.
  3. Many workers wear personal fall protection equipment.  Fact.  Luckily very few workers use it.
  4. Anchors for personal fall protection systems must hold 5,000 pounds.  Fiction.  If the anchor is designed by a qualified person, it must have a safety factor of 2.
  5. If you hook your lanyard (the other end of the rope that is attached to your harness) to an anchor, the anchor must be designed.  Fact.  You cannot guess at the strength of the anchor; if the anchor is not part of a system designed by a qualified person (see #4) the anchor must hold at least 5,000 pounds.  Guessing is not allowed although it appears everybody does it.
  6. The maximum force on the body is limited to 1,800 pounds.  Fact.  This means you better not fall too far before your fall is arrested.  That’s a fancy way of saying that when you reach the end of your rope, the force on your body better be less than 1,800 pounds or there will be two of you.  Incidentally, if the force on your body is limited to 1,800 pounds why does the anchor have to hold 5,000 pounds?  After all, if you pull on one end of the rope with 1,800 pounds, doesn’t the anchor on the other end only have to pull with a force of 1,800 pounds?  Hmmmm-what’s with that?
  7. The 5,000 pound anchor requirement is based on extensive scholarly research and testing. Fiction.  It’s based on the strength of ¾ inch manila rope which is actually 5,400 pounds.  It was lowered to 5,000 pounds in the US federal construction standards to agree with the US federal general industry standards.  So much for science.
  8. You cannot free fall more than 6 feet.  Fiction (sort of).  You can free fall as far as you would like, according to a US federal OSHA Letter of Interpretation.  It’s just that when you get to the end of your free fall, the load on your body cannot be more than 1,800 pounds.  (Now you know how bungee jumping works.)
  9. 100 percent tie off is the same as 100 percent fall protection.  Fiction.  Anybody can do 100 percent tie off; just look at any construction site.  Workers tie off to all sorts of ridiculous stuff.  Like the guy that ties off to the step ladder he is on!  One hundred percent fall protection is easy for scaffold users, but not leading edge scaffold erectors.
  10. I cannot use a scaffold for an anchor.  Fiction.  Some scaffolds make very nice boat anchors.
  11. I can use a scaffold as an anchor.  Fact.  When designed by a qualified person (and perhaps a qualified Professional Engineer) a scaffold can be used as an anchor for a personal fall protection system.
  12. It is difficult to provide adequate anchorage for leading edge erectors and still comply with all the fall protection standards.  Fact.  It’s really tough to get a scaffold to hold 5,000 pounds.  It’s really tough to limit the free fall distance for erectors to 6 feet when they have nothing above them to tie to.  If we waived certain regulations for scaffold erectors, we would eliminate some of the excuses.  For example, is it really necessary for scaffold erectors to have an anchor that can hold 5,000 pounds?  Is it really necessary that the system have a 2 to 1 safety factor.  After all, as long as he/she doesn’t fall to a certain death have we not succeeded?  Something to think about.
  13. Horizontal lifelines are easy to install and use.  Fiction.  While they may be easy to install, they are not easy to use.  The problem with horizontal lifelines is that people never use them.  That’s right; they install them, and hook off but luckily never use them.  If they used them they would be terribly disappointed in the performance of the line.  There is a reason horizontal lifelines are to be designed by a qualified person.  Did you know that an anchor on a horizontal lifeline can see a load of 25,000 pounds if it is not designed properly?  What do you suppose that would do to the scaffold?
  14. All safety consultants and compliance officers are experts in fall protection design and installation.  Fiction.
  15. All scaffold users are experts in fall protection design and installation.  Fiction.
  16. All scaffold erectors are experts in fall protection design and installation.  Fiction.

So much for fall protection– I still think the easiest fall protection is:  Don’t fall.  But then perhaps there’s more fiction in that statement than fact!

Platform or Plank?

By | Resources, Scaffolding, Scaffolding Platforms | No Comments

Is this a tough question?  Is plank a platform or is the platform a plank?  Here is a primer on what constitutes a safe scaffold platform.  Of course, that begs the question as to whether you can have an unsafe platform.  And the answer to that question is pretty easy: yes.  If that is the case, then why are you using an unsafe platform?  Do you know if you are using an unsafe platform?  Now there is a question that is worth answering.  What basis should we use to determine is a platform is safe?  Should we wing it and see what happens?  Should I make up stuff that sounds good so it looks like I’m the guy that knows everything?  Perhaps not.  How about if we use “typical industry practice” and the safety standards as a basis for establishing the criteria for a safe platform?

A scaffold platform can be constructed of many materials although the most common materials include wood plank and manufactured plank.  Wood plank is solid sawn from a tree while manufactured plank can use wood, aluminum, steel or plastic in its composition.  Furthermore, both solid sawn and manufactured planks are usually rectangular and the ends of manufactured plank may be square cut or have hooks on them to hook over the scaffold bearer.  In any event, the planks are purpose built for use with scaffolds.

There are two issues that must be addressed with plank.  The first is the strength of the plank and the second is the installation of the plank.  The strength of the plank is based on the material that is used.  If the plank is solid sawn, that is cut directly from a tree, its’ strength is directly related to the type of tree that it comes from.  In North America the two most common trees that are used for scaffold plank are Southern Yellow Pine and Douglas Fir Larch.  Although less common, Spruce is also used in certain locales.  (This doesn’t mean that you cannot use other trees, such as Balsa Wood, for a scaffold plank.  It’s just that your plank would be really big!  This is due to the fact that the dimensions of the plank are directly related to the strength.  Another way of saying this is the bigger the plank, the more it will support.  Or still another way of looking at it is to say that the weaker the tree, the bigger the plank must be.)  The common size for a scaffold plank is a nominal 2 inches by 10 inches which means that it is actually 1-1/2 inches by 9-1/4 inches.  By specifying that you must use Southern Yellow Pine or Douglas Fir Larch, I then can tell you how much load you can put on that plank, based on a given span.  For example, if you use a Scaffold Grade Southern Yellow Pine plank and span 10 feet, you can safely put 250 pounds on the plank.  If you choose to use Balsa Wood, Willow, or Aspen, all bets are off; it’s time to get a qualified person to tell you what your plank can support.

If you choose to use manufactured plank, the solution is pretty easy:  contact the manufacturer for loading information.  These manufactured plank can be laminated veneer lumber, proprietary plank that use solid sawn wood, aluminum with plywood, all aluminum, steel, or plastic.  While the laminated veneer lumber plank may look like solid sawn plank, the loading characteristics will vary so check with the manufacturer.

The second issue that involves the use of plank is the installation.  The name of the game is to make sure that when you stand on a platform you will remain at that elevation.  It is never good to step on a platform and find out you are quickly descending to a lower unanticipated location.  The end result usually is detrimental to your health.  So, what needs to be done to ensure you stay where you are?  Well that’s easy; make sure the platform is installed correctly.  What does that mean, you ask?  The easy answer is to make sure that whatever you use to construct your platform it will stay where you place it.  With 2×10 plank that means that the plank overhangs its support at least 6 inches but not too much so you create a diving board.  Usually that means a maximum overhang of 12 inches for plank 10 feet and less in length and 18 inches for longer plank.  Of course, if you secure the plank the overhang can be less than the 6 inches and more than the 12 or 18 inches.  For planks that have hooks, the solution is straightforward; use the right length plank for the space.  Other requirements for platforms include:  make sure the space between plank is 1 inch of less; make sure the maximum space between the back edge of the platform and the guardrail is no more than 9-1/2 inches; make sure the platform is close enough to the work surface (depending on the jurisdiction, this distance varies from 3 inches to 18 inches); make sure the platform is not slippery; make sure debris isn’t allowed to pile up on the platform; make sure the platform isn’t overloaded and finally, make sure the scaffold user is properly trained.  Why is this important?  We want to make sure the user understands the platform capacity so it doesn’t get overloaded.  Let’s face it, the only good platform is a safe platform.