A groundplan is the stage seen from directly above, drawn to a stated scale. It is the drawing every other document in a production hangs off: the lighting plot is a groundplan with the rig over it, the section is the same room seen from the side, and a shift plot is a list of movements between positions that only mean anything because the plan defines them.
Reading one is a small skill and worth an afternoon. Almost every convention on the page exists to answer a question a crew will otherwise ask at a load-in, and once you know where the answers live, an unfamiliar plan for an unfamiliar building becomes readable in about a minute.
The view: a plan, not a picture
A plan is a horizontal cut. Imagine slicing the room through at about waist height, lifting the top half away, and looking straight down at what is left. Anything cut through is drawn as a solid line: walls, flats, rostrum edges, the proscenium. Anything below the cut is drawn as it is seen from above, which is why a chair reads as its seat and a table as its top.
Anything above the cut is drawn with a broken line, because it is not really there at the height of the drawing. That single convention carries a lot: fly bars, borders, ceiling pieces, the edge of a balcony, an archway over a doorway. If a line is dashed on a groundplan, the honest reading is "something is up there", and the section drawing is where you find out how high.
There is no perspective and no attempt at realism. It is a measured document, and the whole point of it is that a scale rule recovers the real dimension from the paper.
The two lines everything is measured from
Every position on a theatre plan is described relative to two lines, and both are drawn on the page.
The centre line runs upstage to downstage through the middle of the stage, usually as a long chain-dashed line marked CL. It is the zero of the left and right axis, so a flat set 2.4 meters stage left of centre is described that way, and the same flat mirrored to the other side is the same distance the other way. Symmetry is legible instantly on a plan with a centre line and nearly invisible on one without.
The plaster line runs across the stage along the upstage face of the proscenium arch, marked PL. It is the zero of the upstage and downstage axis, so a rostrum 3 meters upstage of the plaster line is at 3 meters, and something 1.2 meters downstage of it, on the apron, is at minus 1.2. The name is old and literal: the plaster of the proscenium.
Some houses draw a third line, the setting line, parallel to the plaster line and a fixed distance downstage or upstage of it, and set the design from that instead. It is a working convenience rather than a competing standard, and a plan that uses one will say so in or near the title block. When you are handed a drawing, check which line the numbers are measured from before you measure anything. The two lines, the setting line and the marking-out that follows from them have a fuller article of their own.
Stage left and stage right
Directions are given from the performer's point of view, facing the audience. Stage left is therefore the audience's right, and downstage is toward the audience. A plan is drawn with the audience at the bottom of the page, so downstage is down the sheet and stage left is on the right of it, which is briefly confusing for everybody and then never again.
What is on the page
The exact contents vary with the venue and with what the drawing is for, but a working groundplan carries most of the following:
| On the plan | What it tells you |
|---|---|
| Proscenium opening | The width and height of the frame the audience sees through |
| Apron or forestage | Stage in front of the proscenium, often where sightlines get difficult |
| Wings | The offstage space each side, which is where set changes actually happen |
| Masking: legs, borders, tabs | What hides the wings and the rig, and where the sightline is cut |
| Fly bars and LX bars | Broken lines across the stage, numbered from the plaster line upstage |
| Traps, lifts, revolves | Openings and machinery in the deck |
| Get-in, doors, fire exits | How a set arrives, and what cannot be blocked |
| Seating and sightlines | Where the audience is, and lines drawn from the extreme seats |
| Scale, title block | What the drawing is, and what ratio it is drawn at |
Hatching usually means a solid built element cut through by the plan: a wall, a flat, the proscenium walls themselves. Furniture is drawn in outline. Anything drawn in a lighter line weight is usually existing architecture rather than part of the design, which is how a designer's drawing of a set stays distinguishable from the house plan it sits on.
The title block
The title block is the panel in a corner, usually bottom right, and it is not decoration. It carries the production, the venue, the scale, the date, the person who drew it, and a revision letter or number. Two of those matter more than the rest.
The scale matters because a drawing without a stated ratio cannot be measured, only guessed at. The revision matters because the most expensive mistake in scenic production is a workshop building from a superseded drawing. When a plan is reissued, the revision changes, and the drawing that has been on the workshop wall for two weeks is now wrong in ways that are not visible from across the room.
Reading a plan you did not draw
A short order of operations that works on any plan, in any building:
- Find the title block. Note the scale and the revision, and check the date against whatever email brought it to you.
- Find the centre line and the plaster line, and confirm which one the dimensions are measured from.
- Find the proscenium and the apron, so you know which way is downstage without having to work it out from the seating.
- Read the solid lines: that is the set as it will be built.
- Read the broken lines: that is what is over your head, and the section drawing will tell you at what height.
- Look at the wings last, and honestly. Most plans are drawn with attention to the visible stage and optimism about the space either side of it, and a set change is only as good as the room it happens in.
None of this changes when the drawing is made on a screen rather than on a board. The conventions predate the software by a century and outlive every file format, because they were built around the person holding the paper at a fit-up rather than around the tool that produced it.