Theatre Design & Technology - Spring 2008 - 59

Are You Playing with
By rich Dionne

e've all used them: those worn out, screw-hole-ridden, 120-pound, 2x4-framed platforms that seem
so ubiquitous at university, summer-stock, and regional theatres. Or we've used their close cousins:
the 1x6-framed platform, the 1x1 steel-tube-framed
platform. The more adventurous among us have
tried stressed-skin panels, or even sandwich-core
panels. Usually, though, the platforms we use over
and over tend to be the ones that were in stock when we arrived.
When we need to build additional platforms to complement
or replace existing stock, we nearly always build more of the
same. Rarely do we have an opportunity to compare different
platform construction techniques, or to truly consider whether
a technique is more cost-effective or efficient for a specific application. We're usually just too busy. If we could take the time,
though, to examine whether a different deck construction technique might save us time or money, what would we find? Would
it make sense to keep using those ratty 2x4-framed platforms?
Or would it make more sense to build a stock of foam-core
sandwich-core panels?
The answer depends on the situation. Certainly, for some
applications, those tried-and-true, 2x4-framed platforms are
the smartest bet, particularly if there's space to store them, and
lots of burly carpenters to carry them. For other situations-
say, for example, an irregularly shaped deck footprint-the
number of suicide platforms required (not to mention their
awkward framing) might make the use of 2x4-framed platforms
more trouble than it's worth. This article attempts to examine
and compare the advantages and disadvantages of four different
deck construction techniques-plywood sheathing, 2x4-framed
platform, stressed-skin panel, and sandwich-core panel. The
first section of the article will examine structural requirements
for each of the decking types. The second section will examine
the advantages and disadvantages of each surfacing technique

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in terms of material cost, construction labor cost, installation
labor cost, storage cost, and other intangible properties. The
final section will present specific applications and situations
where each technique might be best utilized alone or in tandem
with other techniques. (An examination of steel or aluminumframed platforms would be further enlightening, but is beyond
the scope of this article.)

Part I: Structural analySIS

or the purposes of this analysis, we'll assume that each
surfacing technique-plywood sheathing, 2x4-framed
platform, stressed-skin panel, sandwich-core panel-
are supported by 2x4 stud walls. (Even supporting a
deck 6 feet from the ground, stud walls should be able
to support a load far exceeding that which could be
carried by any of the surfaces they support.) Additionally, we'll assume each deck can support at least a 50
pound per square foot (psf) distributed load. Finally, in
most cases, deflection of the surface plywood or panel
will be noticeable well before a surfacing technique will suffer catastrophic failure under a load; this analysis will assume
a deflection criterion of l/240, unless otherwise stated. (l is
the span length, in inches. On a 2´-8˝ span the maximum deflection would be 1/8˝. See National Design Specification for
more on deflection criteria.) Based on these criteria, specific
construction techniques for each decking method (plywood,
2x4-framed platform, stressed-skin platform, and sandwichcore panel) are laid out below. (For a detailed mathematical
analysis of each decking method see the document entitled
"Shuffling the Deck" at http://web.ics.purdue.edu/~rdionne/
structures.html. Microsoft Excel spreadsheet calculators for
stressed-skin and sandwich-core panels can be found at this
site as well.)

http://web.ics.purdue.edu/~rdionne/

Table of Contents for the Digital Edition of Theatre Design & Technology - Spring 2008