scaffold standards Archives | DH Glabe & Associates

Pop Quiz: 30 Questions About Scaffolding

By | Blog, OSHA Standards & Regulations, Scaffold Bracing, Scaffold Components, Scaffolding, Scaffolding Planks, Scaffolding Platforms | No Comments


It is somewhat surprising how creative workers can get when it involves scaffolding.  Just when it seems all the questions have been answered, along comes a question that raises an issue that was never addressed.  Challenge yourself to these questions and see if your answer agrees with the one given at the end of this article.

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Are You Stable?

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Tarps and other enclosure materials, such as plastic sheeting, are typical materials used to create a desirable work atmosphere.  Many scaffolds are enclosed in screening and debris netting—I recall one resort project in Aruba where the scaffold was wrapped in a mesh to ensure, so I was told, that construction debris would not blow into the adjacent swimming pool.  In reality it was there so the guests below couldn’t see the less than productive construction workers staring at them!  And, of course, now that outdoor temperatures in North America are slowly falling, thoughts of a cozy work environment on a supported scaffold become more frequent, resulting in more scaffolds being wrapped in some type of enclosure so that work can continue.  It is interesting that wrapped scaffolding has been frequently discussed and written about and yet each year scaffolds fall over because somebody wrapped the scaffold without giving much thought to the effects that the enclosure would have on the stability of the scaffold.  Of course, one of the keys to a successfully constructed scaffold is making sure that the scaffold doesn’t fall over; this is especially important for the individuals who happen to be using the scaffold!

The concept of stability is straightforward:  The forces that want to knock the scaffold over have to be resisted.  How can this be done?  While there may be a number of methods that can be used, there are three that are most commonly used by scaffolding designers and erectors:: tying the scaffold to another strong structure that can resist the forces; guying the scaffold tower to a suitable anchor that can resist the forces, and; making the scaffold large enough so the size and weight of the scaffold are adequate to keep the scaffold from falling over.  Since the stability of asupported scaffold is desirable, standards and regulations have been written to address the issue.  The U.S. Federal Occupational Safety & Health Administration, OSHA, requires that “Supported scaffolds with a height to base width ratio of more than four to one (4:1) shall be restrained from tipping by guying, tying, bracing, or equivalent means….” [29 CFR 1926.451(c)(1)]  The standard goes on to require that when the scaffold is tied to an existing structure, it has to be tied at a frequency of no more than 30 feet horizontally and 26 feet vertically for scaffolds wider than 3 feet, and 20 feet vertically for scaffolds 3 feet and narrower.  (In California the requirements are more restrictive.)

Unfortunately, this regulation can be very misleading for the simple reason that it doesn’t address varying field conditions.  Keeping in mind that the OSHA scaffolding standards are minimum requirements and not directions or instructions, the qualified person who designs the scaffold shall determine the proper means and methods for ensuring the stability of a scaffold.  Also keep in mind that a qualified person will not guess at what is required to ensure scaffold stability.  Unfortunately, the reality is that too many scaffold erectors and users think that experience is a great method for determining what it will take to keep the scaffold from falling over.  While the OSHA mandated requirements may work for a scaffold not wrapped in plastic, the same tying requirements will be woefully inadequate for a scaffold wrapped in a tarp and subjected to a violent winter storm.  (Lucky for many wrappers, the enclosure material rips into pieces and blows off before the scaffold is yanked from its’ moorings!)  When a scaffold is wrapped in a quality enclosure, that is a netting or enclosure that is resistant to tearing, the scaffold instead will rip, bend and ultimately fail.

Interestingly, #9 wire is often used to secure a scaffold to a structure.  While this can work with an open scaffold design, it very rarely is adequate for a wrapped scaffold, even if the ties are “doubled up.”  Remember, guessing never has worked well as a substitution for a properly designed and erected scaffold.

So, what is the worker to do?  The answer is easy, logical, and in compliance with the applicable standards and good scaffolding engineering practice.  Have a Qualified Person design the scaffold.  In the case of a wrapped/enclosed scaffold, it will probably take the skills and expertise of a Qualified Professional Engineer who can design the scaffold for the anticipated forces at the specific scaffold location and for the specific time of year that the scaffold will be exposed to external forces from the wind and other environmental conditions.

If you think that you are qualified to design an enclosed scaffold answer yes or no to these statements.  (If you answer no to any of them, you are not qualified to design an enclosed scaffold):

I know where to find the information that tells me what the design wind loads are for my scaffold location;

I am familiar with the American Society of Civil Engineers (ASCE) Standard, Minimum Design Loads for Buildings and Other Structures wind loading criteria;

I know the strength of #9 wire and why it shouldn’t be used for wrapped scaffolds;

I can calculate the forces that are a result of a 100 mph breeze;

I know how to calculate overturning moments and forces due to pressures;

I know what the effects of a partially wrapped scaffold are;

I know what happens if the windows are open;

I know what effects a building corner or roof has on a wrapped scaffold;

I know my limitations.

Federal OSHA 29 CFR 1926.451(c)(2): Foundations and Swivel Jacks Clarification

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

The following is a clarification of OSHA Standard 29 CFR 1926.451(c)(2)(i) which requires that: “Footings shall be level, sound, rigid, and capable of supporting the loaded scaffold without settling or displacement.”

This standard addresses the hazard of a foundation that is insufficient to support the scaffold.  The intent of the standard is to require that scaffold foundations are adequate; that is, they have sufficient strength, are stable, and the footing compensates for non-level surfaces that can introduce horizontal forces which have not been restrained.

The claim has been made that swivel screwjacks cannot be used with scaffolds since they bear on non-level surfaces.  This claim is incorrect since the screwjacks are being used to create the level surface that the standard requires.  While it might be argued that the screwjack is part of the scaffold and consequently must bear on a level surface, this argument is without merit for the simple fact that the swivel screwjack is specifically used for the purpose of bearing on sloped surfaces.

Standards have never precluded the use of swivel jacks with scaffolds.  The truth is quite the opposite: swivel screwjacks are used to create the level surface that is required so that scaffold legs are stable.  Interestingly enough wedges and shims are also used to create a level surface.  By disallowing swivel jacks, it can be argued that wedges and shims cannot be used since they are not part of the foundation but rather are a part of the scaffold.  In other words, if it were not that the scaffold is at a specific location, the wedges and shims would also not be there.

In summary, swivel jacks are a permissible component to be used in the construction of a scaffold.  As with all scaffolds, the scaffold shall be designed by a Qualified Person who will address the issue of horizontal forces when designing the foundation.

Solved Mysteries

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

Experience indicates that certain scaffold safety issues remain unresolved in the minds of those responsible for safety.  More specifically, it appears that fall protection requirements and access requirements are not understood.  So, let’s see if we can sort out the issues.

Fall protection for scaffold users is addressed specifically, and exclusively, in Subpart L of the Occupational Safety and Health Administration, OSHA, Construction Standards while fall protection for “walking/working surfaces” is addressed in Subpart M of the OSHA standards.  What’s the difference?  By definition, a scaffold is “any temporary platform and its supporting structure used to support workers or materials or both.” On the other hand, a walking/working surface means “any surface, whether horizontal or vertical, on which an employee walks or works.”  The significance of all this is that each subpart has a different height threshold when fall protection is required.  Scaffold platforms require fall protection once the platform is ten feet or more above the level below.  For walking/working surfaces, the height is six feet.  There should be no dispute here since the regulations are very clear in this regard.  Subpart M frankly states that scaffolds are excluded (29 CFR 1926.500(a)(2)(i)).  This should be pretty easy to figure out.  Unfortunately there are those who like to believe what isn’t true!

To summarize the issue of fall protection, Subpart L applies to scaffolds, not Subpart M.  Therefore, the height threshold is 10 feet, not 6 feet.  The only exception occurs when using personal fall protection.  In that case, the anchor strength and freefall distances of Subpart M apply, nothing else.  If guardrails are being used for fall protection on a scaffold, then nothing in Subpart M applies.  It’s that simple.

Access is another area where confusion reigns for those who do not fully grasp the relationship between the various subparts of the OSHA standards.  The confusion centers on the use of ladders with scaffolds.  Those unfamiliar with the standards assume  that clamp-on ladders are fixed ladders.  Nothing could be more inaccurate.  The scaffold standards clearly spell out thatportable ladders shall comply with the applicable portions of the ladder standards, Subpart X of the OSHA Construction Standards.  This does not include clamp-on ladders.  Sure, clamp-on ladders are vertical, just like fixed ladders.  But that’s pretty much where the similarities end.  As a matter of fact, there’s simply no way that the fixed ladder standards can apply to ladders used with scaffolds.  OSHA understands that.  In fact, OSHA has clarified this issue by issuing a letter of interpretation that explicitly excludes scaffold clamp-on ladders from the fixed ladder standards.

To summarize, the scaffold standards apply when using clamp-on ladders on scaffolds.  It is true that when using portable ladders, such as extension ladders, certain Subpart X ladder standards apply.  In that case standards addressing strength and dimensional requirements apply, as well as the standards addressing the use of portable ladders.  (These regulations address important aspects of ladder usage such as positioning of the ladder, extension of the ladder above the platform, and using three point contact while climbing the ladder.)

To wrap it up, all this information is readily available.  The regulation that excludes scaffolds in Subpart M (Fall Protection), can be found at 29 CFR 1926.500(a)(2)(i).  The scaffold fall protection requirements can be found at 29 CFR 1926.451(g).  The requirements that apply to the use of portable ladders with scaffolds can be found in Subpart X, (Stairways & Ladders) 29 CFR 1926.1053(b).  And finally, the regulations applying to clamp-on ladders can be found at 29 CFR 1926.451(e)(2).  OSHA Letters of Interpretation can be found at the OSHA website,

Better Access

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Once upon a time, long, long ago, there was a federal agency that developed a set of regulations governing scaffold access.  These regulations were thought to be perfect, or about as perfect as regulations could be.  The scaffold industry was invited to comment on these regulations.  In fact, the whole country was invited to comment on those regulations.  Many came forward to express an opinion.  Contractors, suppliers, manufacturers, wise safety experts, academia, industrialists and regular citizens, expressed their opinions to the agency responsible for the promulgation of the scaffold standards.  Undeterred my the daunting task before them, stalwart governmental employees sifted through the input, inputted the input where reasonable, and finalized the regulations, or standards, that we now know as the scaffold standards.


Included in the standards are regulations governing access for scaffolds.  A number of access options are available to the scaffold erector and user, including stairways, ladders and direct access.  Ladder usage includes portable ladders, such as extension ladders, and attachable ladders, also known as clamp-on ladders.  Now, one would think that clamping a ladder on a scaffold would be straight forward.  Frankly, what possibly could go wrong.  You clamp the ladder on the scaffold, make sure the first step is no more than 24 inches (there’s a regulation that says the first step can be no more than 24 inches – that’s reasonable) run the ladder up to the top of the top platform, and be done with it.  What could be easier?  Well, it appears that the industry has managed to make a simple matter about as difficult as can be imagined.


For starters, there’s the issue of the first step.  What’s with that?  What isn’t to understand about 24 inches?  Most clamp on ladders have a rung spacing of 12 inches.  That would put the first rung at 12 inches, which, amazingly, is less than 24 inches.  One would think that this isn’t an issue.  If your ladder doesn’t fit this scheme, get a different ladder.


Should the worker be forced to get off the ladder at certain intervals?  Good question.  Present regulations allow the ladder to extend straight up the full height of the scaffold, not forcing the user to get off at intermediate stops.  Is this good?  The scaffold designer gets to call the shot on this one.  While the regulations do not require ladder climbers to take a rest, the regulations do require rest platforms at least every 35 feet vertically, should the climber need it.  Forcing the user to use the platform is a decision of the scaffold designer.


Next, the issue of ladder frequency is presented.  How many ladders should we have for a scaffold.  Cleverly, the OSHA standards do not address this issue.  Guess what.  You get to figure it out.  If your scaffold has only one ladder, you have 50 workers on the scaffold, and they have to walk a quarter mile to get to the ladder, you may want to reconsider your strategy!  Should not common sense prevail?  If the workers are tempted to climb the runners because it’s too far to walk to the ladder, then another ladder would be in the best interest of the workers.


The top of the ladder draws a lot of attention from safety minded folks, as well it should.  I’d hate to have the ladder a couple rungs short of a full ladder if I were climbing it.  Interestingly enough, everybody seems to be fixated on a three foot extension of the ladder above the top platform but many seem to be confused as to why.  For that matter, they wonder where the 3 foot dimension comes from, as well they should, since there is no mention of it in the scaffold standards.  No magic here; you need to have something to hang onto as you climb off the ladder onto the top platform.  It doesn’t have to be the ladder although it’s pretty handy.  It can be other things like grab irons and guardrails.  Since it’s easy to run the ladder to the top of the guardrail on many scaffolds, why not do it?


One amazingly baffling issue with attachable ladders is the rest platform.  There is no doubt that the rest platform is a very important element of a vertical, attachable ladder.  Since the ladder is vertical, you would be in a world of hurt if your hands got tired while climbing an attachable ladder and you had no rest platform to climb onto.  I think this is rather evident.  Based on my experience, however, what isn’t evident is the purpose of a rest platform.  There are those who claim that work platforms cannot be used for rest platforms, and rest platforms cannot be used as work platforms.  Why not?  The hazard here is tired hands; the worker needs safe refuge if he/she cannot hang onto the ladder.  Contrary to what you might like, the rest platform is not required to have a couch, TV and refrigerator.  (If you’re that tired, don’t climb the ladder.)  Any platform that is accessible from the ladder may serve as a rest platform.  The writers of the standards meant nothing more, nothing less.


If there is anything controversial with attachable ladders is the issue of accessing the platform.  Is it permissible to climb over or through the guardrail system or is required to have access gates.  This may be the only legitimate question concerning the installation and use of attachable ladders.  I believe the answer is up to the designer of the scaffold.  Federal OSHA does allow climbing over or through the guardrail system.  Scaffold manufacturers have a variety of access devices available for frame, system, and modular scaffolds.  Certain installations do not readily lend themselves to the use of these products; thus the policy of OSHA is a correct one.  It is the scaffold designer that determines the applicability of access gates.


See, this is straightforward.  All scaffold platforms must have proper access.  This access can be an attachable ladder.  The maximum first step shall be no more than 24 inches.  Rest platforms shall be  provided at least every 35 feet vertically.  The ladder can be a straight shot for its full height, although this isn’t recommended, particularly on very tall scaffolds.


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

Here are frequently asked questions concerning scaffolding, applicable standards and regulations.


What is a competent person?

By definition, a competent person is basically an individual who can identify a hazard and has the authority to take corrective action. While the competent person may not have the solution to minimize or eliminate the hazard, the competent person can consult a qualified person to get the solution.


Why should scaffolds be constructed under the supervision of a competent person?

There are at least two reasons. First, a competent person will have the knowledge to identify existing and potential hazards and have the authority to eliminate or minimize those hazards. Secondly, there is a law that says that all scaffolds shall be constructed under the supervision of a competent person.


What does “shall” mean in the Federal OSHA standards?

“Shall” means mandatory. In other words, “you gotta do it!”


Does Federal OSHA require all scaffold erectors be competent persons?

No. All erectors shall be trained and experienced; the supervisor shall be competent.


When is access required for a scaffold platform?

Access is required whenever the height between levels is more than 24 inches.


Can you climb out a window or off of a catwalk to access a scaffold platform?

Yes you can, provided the platform is no more than 24 inches above or below the point of access, and the platform is no more than 14 inches horizontally from the point of access.


Are guardrails required on all scaffold platforms more than ten feet above the level below?

No, but fall protection, either personal fall protection equipment, or a guardrail system, is required.


How strong does a guardrail have to be on a supported scaffold?

The toprail shall withstand 200 pounds in any direction except up on the rail, and the midrail must withstand 150 pounds in any direction except up at any point on the rail.


Do all supported scaffolds need a base plate?

Absolutely, unless the scaffold is a mobile scaffold in which case you shall use locking casters.


How wide does a scaffold platform have to be?

The minimum width of a platform is 18 inches unless you can show that an 18 inch wide platform will not fit in the space allotted. There is no maximum width of platform.


Do scaffold erectors have to always use personal fall arrest equipment?



Who determines if erectors must use personal fall arrest equipment?

The employer’s competent person determines in the erectors shall wear and use personal fall protection equipment.


Is it a good idea to use scaffold grade plank?

It is an excellent idea! The SIA strongly encourages the use of scaffold grade plank unless the plank being used has been designed for such use by a qualified person.


Can scaffold equipment of various manufacturers be intermixed?

Manufacturers discourage intermixing equipment because of the risk of incompatible equipment. The SIA approves of equipment intermixing only if the equipment is compatible. In other words, if you don’t know the hazards of intermixing equipment of various manufacturers, don’t do it.


Is it necessary to train scaffold erectors?

Yes; it is required by law.


Is it necessary to train scaffold users?

Yes; it is required by law.


Does Federal OSHA require all scaffolds to be designed by a qualified person?



Is continuous cross bracing required on all frame scaffolds?

No. While it is a good idea to install continuous bracing, and manufacturers recommend it, continuous bracing is not required provided proper bracing is installed. If you don’t know what proper bracing is, install continuous bracing.


Are clamp-on ladders considered “fixed” ladders and consequently must comply with Federal OSHA Subpart X standards?

No. Clamp-on ladders are a scaffold component and consequently are addressed in the scaffold standards, Subpart L. Clamp-on ladders are not fixed ladders.


How far above the platform should the ladder extend?

Unless there is a handhold such as an access gate panel or other hand grab, good construction practice suggests the ladder should extend above the platform about 36 inches. There are no Federal OSHA scaffold standards that specify a height unless a portable ladder is used. If a portable ladder (manufactured extension, fixed length, step, or job-built ladder) is used, the minimum height above platform is 36 inches unless the ladder is secured and a hand hold is provided.


When are toeboards required?

Toeboards are one form of falling object protection when there is a danger of injury to workers on lower levels of the scaffold. Other forms of falling object protection include canopies, barriers, screens, and catch platforms.


Who determines safe access for scaffold erectors?

The competent person makes the determination.


Is it okay to climb over the guardrail to access a platform?

Yes, although an access gate panel would make access a lot easier.


Federal OSHA requires for erectors that “hook-on or attachable ladders shall be installed as soon as possible as scaffold erection has progressed to a point that permits safe installation and use.” If the erectors are constructing a stair tower and installing the stair units as the tower is constructed, do the erectors have to install a ladder to be in compliance with the standards?

I would certainly hope not! Look at the intent of the regulation. Its intent is to protect the erector as best as possible. Stairs would provide that protection.