PLATFORMS

Platforms, parellels, stairways and ramps:

Required whenever a variation in floor levels is needed.
Platforms: most common units for adjusting elevations.
Two types:
	* Rigid platform, a.k.a. platform
	* Parellel, a platform with a removable top and a folding frame.

Platform Tops: usually made of plywood.
   • 3/4" is the usual thickness.
   • 5/8" is sometimes preferred for a small weight savings.
A theatre should stick to one or the other, though, to simplify legging.

Platforms usually made in 4x8 units, or in some even division thereof.
Rigid platforms usually made with frames of either 2x4, or 1x6.

2x4s very commonly used.
	* Wood is readily available, cheap and can be assembled with a variety 
        of fasteners.
	* Finished platform is 4 1/4" thick, takes less storage space per platform 
        than any other material generally used.
	* Construction grade lumber is sufficient, although #2 is better.
As disadvantages:
	* 2x4 platforms must almost always be legged when used.
	* Must be faced with 1/4 ply to give a smooth face, even on the bottom 
        level.

1x6 platforms are another common alternative.
	* 1x6 weighs about a quarter less than 2x4, but almost identical in strength.
	* Need not be legged or faced when used for a 6" rise. 
        When legged, offers longer diagonal for the bolts.
On the minus side:
	* 1x6 costs more, needs better quality board than for 2x4.
#2 is the minimum, and Select is better.
	* Each unit takes more space to store.
	* 1x6 splits easier, more care must be taken with choice and placement of 
        fasteners when assembling. This tends to negate the longer bolt diagonal 
        of legs, so needs as much bracing as 2x4 platforms.

Warning: personal bias here!

For my money, 1x6 platforms are easier to use, but 2x4 platforms are cheaper to 
build and store, so I usually build 2x4.

For greater stength and semi-permantent installation, platforms may be made with 
2x6 instead of 2x4.

Too heavy for stock use.

Platforms are built with the frame lumber on edge, with bracing added in the middle.
Number of braces varies with personal taste.

Plywood platforms
	* Sides are cut to the desired height.
	* Holes are cut out to reduce weight, and the pieces are fitted together.
	* Glue-blocks must be used to hold joints together.
	* These platforms are strong, fairly light, and already built to the height 
        desired.
	* Very quick to set up, easy to face.
However:
	* Very bulky to store, do not lend themselves to legging to other heights.

Legging platforms

Greatest advantage of standard platforms is ability to leg to varying heights. 
Three common methods for wooden platforms.

Simple bolted leg
A leg, usually 2x4, bolted in place with two 3/8" carriage bolts.
System is simple, direct, and reasonably strong.
*however*
Weight is carried only on the bolts and bolt holes, and if there is too much 
weight, the platform frame may split or the bolts might shift, causing lid to pop.

Compression or step legs:
Attached with 1/4" bolts rather than 3/8" bolts, often flathead rather than 
carriage bolts. On platforms a foot or less high,  drywall screws may be used to 
secure the legs.
WARNING: these may strip out or snap off if the platform is used hard.
On the minus side: takes more time and materials to make these legs, but the 
extra strength and ease assembly makes it worth it.  As you can tell, they are my 
preferred leg.

Leg Placement
Be sure legs placed  no further apart than 4 ft.
Otherwise, may be bouncy, and platform may break under heavy or synchronous loading.

Tressles
Built like stud walls in a house:
   Top and bottom plate and a verical "stud" legs on two to four foot centers.
The stud frame overall is the height of the deck minus the thickness of the 
platforms.
Is a decking system rather than individually legged platforms fastened together.

Tressles may be built as stock and stored for future use.

Tressles slower to built, bulky to store, but allow extremely fast assembly of 
large decks (once tressles are built.)

Are very strong and stable.

Particularly suitable for raked decks. Miss Saigon deck built this way 
(of aluminum).

Cross Bracing

Whatever leg system is used, if legs are taller than a foot or so, need to add 
cross bracing.

Up to two feet: you probably need brace only the narrow side of the leg.

Above two feet: crossbrace both directions.  The taller the leg, the more bracing 
is needed.

Parallels
An alternative to the rigid platform.

A series of tressles built of 1x stock set flat rather than on edge like tressles. 
Hinged together to make a folding platform frame rather than a rigid one.

Frames built like standard flats with cornerblocks and keystones, then are 
hinged together to fold when lid is removed, but are held rigidly open when the 
lid is in place.

Parallels come in two flavors, Standard and Continental.

Standard Parellel
Frames hinged together so frame folds like a big parellelogram.
Standard parallels can be almost any size so long as the ends and sides are 
parallel.
	* Can be square, rectilinear, or even a skewed parellelogram.
	* Requires fewer parts than equivilent continental parallel.
	* The major drawback is storage space.

Continental Parallel

Ends and center frames still all identical in size, and fit inside full 
length side frames

                            *but*

Short frames made of two identical individual frames.

Instead of five frames, you need eight frames for the same 4x8 parallel.

Biggest advantage: the frame when folded is the same length as the opened 
platform.

When folded, they are thicker but shorter than standard parellels, so are much 
easier to store.

More restrictions on the size of continental parellels.

Ends cannot be longer than 1/2 the length of the sides.  Otherwise, frames 
cannot fold completely. Extra care must be taken with placing center frame. 
When width is 1/2 the length, the center frame must be slightly off center, 
so that the edge, not the center, of the center frame is center on the parellel.
Thus, it can fold completely without hitting the folded end frame.

Plywood Parellels
Also possible to make parellels out of plywood, by hinging rather than gluing 
them together. Easier to get the parts of the frame same size and square than 
with traditional parellels, but are inherantly weaker as the hinge screws are 
more likely to rip out of the plywood.

Platform lids
	* Usually made of 3/4 plywood.
	* CDX is usually sufficient
	* AC or BC may be used instead if appearance matters.
	* 5/8" plywood OK for a small weight reduction, but don't go any lower, 
or the platform will be bouncy.

Metal Platforms and parellels
Common in professional theatre to use steel or aluminum tubing in place of wood.

Metal thinner and lighter in same strength platforms
*but*

Requires metal working equipment to build.

Construction principles similar, but use welding rather tan mechanical fasteners.

Especially suitable for road shows due to durability.