Platform or Plank?

By David H. Glabe, P.E. / May 1, 2010

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.

Tags: Scaffolding Scaffolding Platforms plank platform Resources wood platform

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