Factor This – Scaffolding Safety Factors

By David H. Glabe, P.E. / April 20, 2016

When it comes to safety, as the saying goes, you can never have too much.  Nice saying, but not very realistic, is it?  If guardrails are good, then a safety net and personal fall arrest equipment are even better, some may say.  Fortunately, reasonable people think reasonably and do the reasonable thing and accept a level of risk commensurate with the task at hand.  That’s a fancy way of saying that not everything can be safe all the time.  After all, while the ship has a life boat, I don’t think any life boats have life boats.

So goes it with safety factors.  A safety factor is used to reduce the risk of failure of a product, component or system.  Simply stated, a safety factor means making the product stronger than it needs to be. There is 2 to 1 safety factor that is required for designed fall protection according to OSHA.  An automobile is designed so the suspension components don’t break even when you insist on giving ten of your closest friends a ride in you four seat car.  And even scaffolds have safety factors so they don’t fail when abused.

The size or magnitude of a safety factor varies depending on the product, the conditions in which it is used, the risk to humans when a failure occurs, and the importance of the component or structure in society.  For example, it is important to make sure the hospital remains standing in the event of an unexpected event while the adjacent wood shed can fail without any risk to humans due to the same event.  Similarly, materials may have different safety factors due to the variability within the material.  Steel is produced using a very precise process that controls the content of iron and other metals; this makes the resulting steel very consistent in its properties.  Solid sawn wood on the other hand varies greatly in its internal structure resulting in a material that varies in its strength.

Supported scaffold products have a high safety factor although the steel strength is predictable.  This is due to the expected use of the products and the knowledge that a given scaffold product may be damaged, may be used incorrectly and will probably be overloaded.  For example, wire rope used in suspended scaffolds has a higher safety factor, 6 to 1, for two reasons: the first is that the rope can be damaged easily and the second is that if the rope fails, the results can be catastrophic.  Other scaffold components have a safety factor of 4 to 1.  This means the scaffold can support four times the load that is expected to be applied to it.  This is a rather high factor compared to the typical structure where the safety factor is about 1.6.  That’s right; it can be argued that a properly constructed scaffold is safer than the building you are in.  Of course it is assumed that the scaffold is constructed properly and therein lays the bigger problem.

There are regulations and codes that specify that the typical scaffold must have a safety factor of at least four.  To achieve compliance with that standard a worker must know two important pieces of information: first, how much can the scaffold support and, secondly how much load is being placed on the scaffold.  If every scaffold user had the answer to those two questions, the scaffold safety factor could be 2 or less.   Unfortunately, most workers don’t know either of those loads—they only know the scaffold works.  They have no clue as to capacity nor do they apparently care –they just know it works.  And when the scaffold collapses, they blame the scaffold!

Amazingly, even the so-called experts get in on the action.  They analyze, contemplate, agonize, deliberate and finally conclude that the scaffold should have been stronger, confident in their ability to wisely conclude the obvious.  It’s like blaming a car crash on the fact that the car ran into something.

One drawback of a high safety factor is the inefficiency it builds into every project.  It’s like paying four times what is necessary.  It requires moving four times the equipment.  It requires four times the counterweights for a swing stage outrigger beam.  (Don’t ever tell the erectors they are dragging four times the necessary counterweights to the roof because they’ll quit!)  On the other hand, the high safety factor allows the worker to be lazy.  There is no need to figure out the weight of the stuff going on the scaffold because it will probably work.  There is no need to find out what the scaffold can hold because past practice shows there are no problems.  Nice attitude, but how close are you to failure?  Wouldn’t you like to know if you are living life on the edge?

Even scaffold manufacturers and suppliers live life on the edge.  While it is hard to believe, some manufacturers and suppliers have no idea what their equipment can hold.  They either have no load charts or steal the information from those who do know.  How often have you heard that “my equipment is as good as their equipment,” or better yet, “use so-and-so’s load chart for my stuff!”  Certain attorneys would love to hear that.

Do you like living on the edge?  Do you feel lucky?  If you do, or you don’t know the capacity of the scaffold you are using, there is good news.  OSHA compliance officers don’t know either.  Therefore, the possibility that you will be cited for non-compliance with 29 CFR 1926.451(a)(1) is really remote.  At least until the scaffold you are standing on collapses with you on it.

Tags: Scaffolding Blog OSHA Safety

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David H. Glabe, P.E.

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