It’s Just Wrong

By David H. Glabe, P.E. / February 1, 2004

There is no diplomatic way to state this but to say it’s just wrong.  I’m speaking of the misguided idea that platforms constructed by placing plywood on scaffold planks is not allowed under the present U.S. Federal regulations governing the construction and use of scaffolds in the United States.  More specifically, there apparently are safety officers and OSHA compliance officers who claim that placing plywood decking on top of scaffold planks is hazardous and consequently in violation of the scaffold standards.  I believe there are two issues involved with this subject.  The first issue involves the construction of the platform while the second issue involves the scaffold regulations issued by the Federal Occupational Safety and Health Administration, OSHA.


Platform Construction


Let’s take a look at the construction of a scaffold platform that consists of a plywood deck supported by structural members which in turn, are supported by scaffold components.  A deck of this design can be compared to a wood floor in a house or apartment building.  The plywood, or other decking material, is supported by structural members that are spaced in equal increments.  The designer of the platform must consider two aspects.  First, the decking and supporting structural members must be strong enough to support the anticipated loads and secondly, the platform must be designed so it doesn’t fall down during use.  From an engineering standpoint, it is a relatively easy task to determine the strength of the components.  It is also relatively easy to conjure up a design that won’t collapse during use.  Of course, once the design of the platform and its’ supporting structure has been determined, it is up to the erector to construct the platform so it conforms to the design that presumably is correct.  Assuming the scaffold platform is accurately designed, and correctly constructed, the user can be assured that he/she will have a safe work experience.


But, what is a properly constructed scaffold platform?  It will be a platform that obviously is strong enough for the anticipated loads.  It will be a platform that will not have excessive deflection.  It will be a platform where the components will not slip off the supports.  It will be a platform that can be visually inspected.  It will be a platform that is sufficiently wide.  What kind of platforms meets these conditions?  A properly constructed plywood/plank deck easily meets all these expectations. It will be strong enough (4:1 safety factor), limit the deflection, be secured from movement, be smooth surfaced, and be easily inspected from underneath where potential damage can be seen.  In fact, all kinds of platforms can meet these specifications; the variety of possible platforms is limited only by the imagination of the designer.


The Regulatory Question


How then does such a platform comply with the recognized standards?  Rather well, thank you.  Unfortunately, there are those who believe that several standards may be violated.  At issue is whether this type of platform complies with standards for fabricated decks, whether this type of platform exceeds the allowable deflection standards, and whether an adequate inspection can be made.


Fabricated Deck Issue


The claim is that the deck must be a fabricated deck or plank only.  Keep in mind that, by OSHA definition, a platform “means a work surface elevated above lower levels.”   Therefore, the platform can be constructed of many materials.  In fact, the platform can be constructed of Styrofoam® if it is strong enough and meets the deflection criteria prescribed in the standards.  Also keep in mind that by OSHA definition, a fabricated deck “means manufactured platforms made of wood, metal or other materials.”  A platform constructed of plywood and scaffold plank is not a fabricated deck because it is not manufactured but rather assembled from two wood products.  The fact is that the OSHA standards do not require that platforms be built with fabricated decks.  What OSHA does require is that platforms have sufficient strength, are at least 18 inches wide, don’t have any large openings, and have a fall protection system when the elevated platform is more than ten feet above the level below.  So much for saying the platform must be a fabricated deck!


The Deflection Issue


The claim is that a plywood/plank deck will exceed the allowable deflection regulations.  This is ludicrous.  The OSHA standards specify that scaffold platform deflection must be limited to one sixtieth of the span.  This means, for example, that a platform can’t bend down more than 2 inches in a 10 foot span.  This regulation says nothing about the materials that are used.  You can use anything you want, just don’t let it bend too much.  The qualified person can determine how much a plywood and plank deck will deflect; that’s part of the design process.  Therefore a plywood/plank deck can be designed so the deflection is within the regulatory limits.  So much for saying that a plywood and plank platform will deflect too much!


The Inspection Issue


How about inspection?  The OSHA standards require that scaffolds “shall be inspected for visible defects by a competent person…”  Some people are concerned that the plank cannot be seen if there is plywood on top of it.  Well, the real concern should be on the underside, where the plank, and the plywood, will show evidence of failure long before the top indicates anything.  Besides, this allegation is no different than saying the plank should be lifted off their supports daily for an inspection of the scaffold bearer, or the sill should be disassembled so the foundation can be inspected.




The bottom line here is that a plywood and plank platform makes a very nice working surface that is safe and functional, assuming it is properly designed and constructed.   To say that these types of properly constructed platforms are a violation of applicable standards is an unreasonable, bizarre interpretation of the standards and a complete misunderstanding of safe scaffold construction.

Tags: Scaffolding Scaffolding Planks Scaffolding Platforms OSHA Standards & Regulations plank safety hazards platform safety hazards Resources Safety Hazards scaffold inspection

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