FEATURE BY JUSTIN “JW” WITTWER WITH JEFF JACK PLYWOOD FOR ACCESS SCAFFOLDING DOES IT MATTER WHICH PLYWOOD IS USED IN SCAFFOLDS? THIS ARTICLE EXPLORES THE FACTORS THAT SHOULD BE CONSIDERED IN SELECTING PLYWOOD.

28 MARCH/APRIL 2018 lywood is used reach different elevations folds must be designed by a as they can create overload in the scaffold- of a unique design, for ex- qualified person and further for plywood due to either ing and access ample, a “dance floor” with defines a qualified person as: localized fiber crushing or P world every a rolling tower to access the “One who by possession of a rolling shear. day. Wood plank is used to interior finishes of a domed recognized degree, certificate, • Face grain direction. cover gaps and holes in a structure; and or professional standing, or Plywood has both a strong platform where piping and • Covering gaps where pip- who by extensive knowledge, direction and a weak direc- other obstructions protrude ing and other object stick training and experience, has tion for carrying loads to through the scaffold and up through the platform successfully demonstrated supports, and the difference chop the deck into a mince- where additional planking his ability to solve or resolve between these two orienta- meat sandwich. On a large cannot fit. problems relating to the sub- tions significantly affects industrial project, plywood Those are just a few ject matter, the work, or the the design carrying capac- can be one of the largest examples of how plywood is project.” ity; plywood is strongest consumable costs, depending used in the scaffold industry. In consulting two of the when the grain direction upon the facility and the type To use plywood correctly most qualified persons, David of the face veneers is per- of scaffold. There are a lot of and safely, one must fully H. Glabe, P.E., president of pendicular to the members solutions available to cover understand how the scaffold Glabe Consulting Services supporting the plywood. gaps, from steel plank fillers is going to be used, includ- Inc. and founder and partner • Number of plies. A greater to smaller plank that hook ing considering uses beyond of DH Glabe & Associates, number of plies improves into the side to cover gaps what might be expected. In and Dale Lindemer, P.E., randomization of strength- where protrusions exist, but the instance of large area vice president of Access reducing characteristics plywood remains the most scaffolds, or “dance floors,” if Engineering at BrandSafway, (e.g. knots), which in turn common in the marketplace one cannot reach the soffit, it there seemed to be consensus results in a more consis- today. is likely that a ladder is going that three-fourths-inch CDX tent product that can be Some of the more com- to be placed on the deck at is most commonly used. But designed using higher mon uses of plywood in some point. Or, in the enter- is that the correct type of allowable stresses. access scaffolding are: tainment world, someone is plywood to incorporate into • Stress grade level. Vari- • Covering large-area scaf- likely to roll a trunk of rig- a scaffold design? Glabe and ous grades of structural folds to reduce the scaffold ging, shackles, nylon slings, Lindemer agreed that there plywood are defined in plank count, also known as etc., across the deck; that are at least four factors to con- the National Institute of skip planking, or to utilize trunk could weigh in excess sider in selecting plywood: Standards and Technology a multi-span joist, like of 2,000 pounds carried on • Point loads implied. Larger (NIST) Voluntary Product aluminum beams; four 2-inch wide casters. loads occurring over a Standard PS-1 for Struc- • Covering large-area scaf- The Occupational Safety small footprint (such as leg tural Plywood. The APA folds for a rolling tower to and Health Administration loads on a tower) may re- – The Engineered Wood be erected on top of it to (OSHA) requires that all scaf- quire special consideration Association (APA/EWPA)

SCAFFOLD & ACCESS MAGAZINE 29 WHAT IS CDX PLYWOOD? “CDX” stands for “CD-Exposure 1” plywood. The first two letters are used to designate the exposed face grading; C represents the “front” side and D the “back” side. Compared with A-grade plywood, C-grade plywood will have a rougher finish with visible knots and knotholes. CD plywood is generally considered construction-grade plywood. The X stands for exposure and means that the plywood has been made using exposure-resistant glue. Ezwoodshop.com notes that the plywood “is tough enough to withstand a little moisture—but for only a short time.”

publishes allowable design He is a qualified person and Much of the plywood stresses for various grades that stated, “Part of the qualifications a qualified person can use in of a qualified person, as defined used in scaffolding design and selection. For more by OSHA, is knowing where information on plywood grad- those qualifications end and today is ¾-inch CDX, ing, visit https://www.apawood. when to seek outside counsel. but is that the correct org/plywood. • I’m smart enough to know when to seek the guidance of those who type of plywood to About the Author know more than I do. Hence my Justin (JW) Wittwer, owner exchange with Mr. Glabe and incorporate into of Event Staging Systems Mr. Lindemer. I’m grateful for a scaffold design? and a planner/scheduler for their assistance in assembling this Brock Services, is a member information, which reminds me There are at least four of the Plank and Platform of a joke, ‘What’s the only thing Council. He can be reached at you can get two engineers to factors to consider. 1-833-STAGING (833-782-4464). agree on?’”

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