Construction of Stairs for the Stage: 2

While many of the practices for constructing stairs for the stage rely upon the brute structural strength of certain members of the unit, those same practices tend to result in  units that are heavier than necessary.  Much as unit-body construction in the automobile industry lead  to cars that are lighter and stronger, constructing scenery for the stage in a manner where every part contributes to the strength of the overall unit, can yield to improved strength and to savings in weight.

In the case of the stair unit, one key is to enlist the riser as a weight-bearing feature.  Other strategies to creating stronger construction include eliminating fastener-into-edge of plywood joints, enlisting face-to-face glue joints and relying on compression to support members where possible. Below is an orthographic drawing for a stair unit that we recently built for a production of Alice’s Trip (a theatrical piece devised by colleague Jennifer Nostrala based upon Alice in Wonderland by Lewis Carrol).

This unit is an open-carriage dependent stair.  Notice that it is 6′ in width, but features only two carriages (one at each end).  Rather than relying upon multiple internal carriages or upon beefy stringers, the riser provides the horizontal structural support for the treads.  While the riser is constructed of 1/2″ ply in this case, I often use 1/4″ ply for the riser in step units of 4′ width or less.

Each riser is firmly attached to stringers made of 1×2″ true lumber.  I often use 1×2 (3/4″ x 1 1/2″) with good results. The stringers are securely glued to the riser.  Fasteners such as staples or screws hold the parts firmly together while the glue dries, creating a member not unlike the manufactured I-Beam joists used in much modern home construction. The riser is attached to the carriage with fasteners through the face of the riser into the edge of the carriage and  by  fasteners through the carriage and into the stringers.

In order for the riser to pick up both stringers, it must notch around the carriage below the lower step.   The notched riser minimally increases construction time, but serves an additional structural purpose.  The notched riser transfers the weight of the attached steps to the carriage through the notches.

Photo of Alice’s Trip step unit under construction showing carriages and 6 of the 8 stringers.

I prefer to cut he carriage is cut out of 3/4″ plywood instead of out of lumber.   I find 3/4″ ply more uniform, stable, dependable and cheaper than 1x 12 which often features knots, cupping and warpage.  Since the maximum length of standard  3/4″ plywood is 8′, I can usually build a stair unit of up to 7 steps with unbroken  3/4″ ply carriages.  Normally, I rip the plywood to 12″ and cut the sawtooth profile of the stair from one side.  If the stair will require a lot of weight, or on the longer spans, I rip the plywood to a wider width (14″ or so) if the design of the stairs will permit.  For taller units with more than 7 steps, I have laminated layers of 1/2″ ply or 3/4″ play to create the equivalent of an engineered beam.  I try to avoid using 2×12 for open-carriage stair carriages because of issues with quality and uniformity and the tendency of the points of the saw-tooth profile to chip off along the grain lines.

As a rule, I build dependent style step units.  Though it would be easy enough to build 3 or 4 step units  in independent style, I find that dependent construction reduces material (potentially cost) and weight.  The dependent style stair usually stores more compactly than the independent stair and this helps to maximize the limited storage that plagues many theatres.   As I pointed out in last week’s blog, If  one needs a self-supporting stair unit, it is usually not much of a chore to add some legs to the elevated end of a dependent unit to transform it temporarily into an independent one.

Every step in a step unit consists of a Rise (the height from one step tread to another) and a Run (roughly the depth of the tread).  Though humans are quite varied and adaptable, there is only a small range of rise and run combinations that can be comfortably navigated by a person climbing stairs.  I use, what I call “the rule of 18”.   Simply stated, this rule restricts the sum of the rise and the run of a single step to 18″.  Thus, a step with a 6″ rise requires a 12″ deep step.  Similarly an 8″ rise dictates a 10″ run while a 9″ rise would require a 9″ run.    In practice, I have found that anything outside of a 6″ to 8″ rise is uncomfortable for an actor to navigate.

If you were to measure the steps in your home or place of employment, you would probably find that architectural standard tends to fall closer to 17 1/2 inches instead of 18.  I have not found that there is much of a difference in comfort between the two and the benefit of not having to work in halves of inches of elevation is usually quite helpful.  The steps of the Alice’s Trip stair unit consists of 6 1/2″ rise and 11 1/2″ run.

Another guideline that I adhere to is that every step in a run of stairs should be of uniform rise and run  This is because as a person walks up and down a stair, he or she becomes accustomed to the muscle patterns required to climb or descend them.  When navigating stairs, one becomes accustomed to relying on automatic processes freeing up concentration for matters other than climbing the stairs.  This is especially true of the actor on stage. Ascending or descending irregular steps requires full concentration and the lack of it, can be disastrous.    By extension, I have found that it is best that all steps on an entire set (including escape stairs) conform to the same ratio.

That’s enough for now! Have fun!  Be safe!

SJM

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