A client asks whether the hallway will feel too narrow. An architect does not stand in a field and wait for it to be built. She sketches the hallway in plan, then in section, then from eye level, and in thirty seconds she can see that the ceiling is the problem, not the width. The drawing was not a record of a decision. It was how the decision got made.
This is the difference between an architectural drawing and the engineering drawing in Engineering Drawing & CAD (34/18). An engineering drawing is mostly a contract: this part, to this tolerance. An architect's drawing is that too, in the final set, but most of the drawings an architect makes never reach a builder. They are thinking tools, test rigs and sales pitches. A student spends a year learning which drawing answers which question.
Who takes it: every architecture student, in the first or second year, usually alongside the first design studios; interior, landscape and urban design programmes teach versions of it. Schools of the studio tradition (the Bartlett, ETH Zurich, MIT) lean on hand drawing and model making; many professional programmes add digital modelling in the same year.
What it's for: choosing the right kind of drawing to explore, test or communicate a design, and reading the drawings other people make.
Comes after: Form, Space & Order (34/89).
Leads to: Building Technology (34/93) and the studio capstone The Design Studio (34/96); it is the architect's cousin of Engineering Drawing & CAD (34/18).
Honest line: you won't learn a drawing program, and you won't become a good draftsperson from reading. You will be able to read a plan, a section and an elevation of a real building, and know what each is for. Easier first reads: Perspective (08/07) and How to Read a Building (08/10).
Architects draw for three reasons, and mixing them up is a beginner's mistake. First, to explore: a fast, loose sketch to find out what you think. It should be cheap enough to throw away fifty of. Second, to test: a measured drawing in which you ask a specific question (does the stair fit? how high is the room?) and the drawing answers it, because the lines are to scale. Third, to tell: a presentation drawing, a render or a final construction set that explains the design to a client, a council or a builder.
A famous early case of drawing used as an instruction comes from China. The Song-dynasty building manual Yingzao Fashi, compiled by Li Jie and published by the Chinese court in 1103, standardised timber-frame construction with written rules and illustrations (the drawings we have come through later editions). Builders could work from it across the empire. That is the "tell" job of drawing, long before CAD.
The reason architects insist on drawing by hand while computers do it faster is the first job. A hand sketch is slow enough to think in and loose enough to leave room for a surprise. Not every architect agrees, and the research that would settle it is thin: many successful designers work almost wholly on screen. Whichever you prefer, the point stands: the drawing is the thinking.
Each kind of drawing is a different question put to a design.
Building drawings split into two families. The orthographic family projects every point straight onto a flat surface along parallel lines. The three members you need are the plan (a slice seen from above), the section (a slice seen from the side) and the elevation (the outside face, seen straight on). Because the lines are parallel, a length parallel to the page is drawn true, which is why you can measure it with a scale rule. The price is that nothing converges, so an orthographic view looks flat and a bit unreal.
The second family adds a third dimension. An axonometric drawing (isometric is the best-known kind) turns the object so you see three faces at once but keeps the lines parallel. You lose nothing in measurability, but all three directions are drawn short by the same amount (about 82% in true isometric). A perspective makes lines converge as they do in the eye. Try all four on one small house.
The house is 8 m wide, 6 m deep and 3 m to the eaves, with a gable roof 1.5 m high, a door and two windows. It is drawn as a wireframe (no hidden lines removed) and the drawing is rescaled to fill the frame each time, so measure the percentages in the readout, not the pixels.
Plan and elevation show exactly one face of reality, and that is their strength: each answers one question without distraction. The plan answers "what goes where?", the elevation "what does it look like from outside?", and the section "how tall, how thick, how do the floors meet?" Axonometrics are favourites for explaining a building in one image, and some architects have used them as an analytical tool: Auguste Choisy's "worm's-eye" axonometrics in his Histoire de l'architecture (1899) show structure from below, so you see how it holds up, not just how it looks.
Perspective is the drawing that shows what a person would see. The idea that makes it work is simple: parallel lines going away from you meet at a point on the horizon, and the horizon is always at the height of your eyes. That is why the line sits at your eye level whether you stand on a hill or lie on a floor, and why everyone who is as tall as your eyes is cut by the horizon at exactly eye height, whether they stand near or far.
In the early fifteenth century, according to his biographer, the Florentine architect Filippo Brunelleschi demonstrated this with a painted panel of the Baptistery and a mirror, and the theory was written down by Leon Battista Alberti in De pictura (1435). The Renaissance did not invent seeing in perspective; it invented a rule for drawing it. Other traditions chose other rules: Chinese and Japanese scroll painting often used parallel or shifting viewpoints, which suit a picture you read across a table, not one you stand inside. Neither is wrong; they answer different questions. (The library's piece Perspective, 08/07, goes into the art side; here we use the geometry.)
A hall 6 m wide with 1 m floor tiles, seen with a pinhole camera. Three figures stand at 3, 4.5 and 7 m: a child 1.0 m tall, a man 1.7 m and a tall one 2.0 m. Their heads are drawn as dots.
Drag the eye down to 0.3 m, a dog's-eye view: the horizon drops and everyone towers above it. Raise it to 3 m and you look down on everyone. The practical use is bigger than it seems: to draw a believable room, choose the eye height first, and everything else follows from where the horizon is.
A drawing of a building is far smaller than the building, so every drawing has a scale, a ratio of drawn length to real length. In countries that use the metric system, architects work in 1:20, 1:50, 1:100, 1:200 and 1:500; in the US, imperial equivalents such as 1/4 inch to the foot (1:48) are common. At 1:100, one millimetre on paper is 100 mm, one tenth of a metre, in reality, so a 3.6 m room is 36 mm. Small scales (1:500) show a site and big scales (1:20) show a window detail. Using the wrong scale is a classic way to fail a first-year drawing: draw a 1:20 detail on a 1:500 site plan and it disappears into a dot.
Paper sizes follow the same logic. The ISO A series (A4, A3, A2, A1, A0) is built so that each sheet is half the one before it and every sheet is the same 1 : √2 shape, which means a drawing enlarges or shrinks neatly from one size to the next. A0 has an area of one square metre. Try fitting a building on a sheet.
Standard scales used: 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000, 1:2000; the sheet has a 20 mm margin all round and is used in landscape or portrait, whichever fits better.
The last slider is a lesson. Shrink a drawing marked "1:100" on a photocopier to 70% and the label is a lie: the real scale is now 1:143. This is why professional drawings carry a graphic scale, a ruler printed on the sheet, which shrinks with the drawing and stays true. The numbers on the page are a promise; the bar is a measurement.
A plan hides height completely, and height is where most trouble lives: head-bumping stairs, ceilings that press down, floors that do not meet. A section answers these, and the best single example is a staircase. A stair is a repeated step of rise (the height of each step) and going (its depth), and your body prefers a narrow range. In the seventeenth century the French architect François Blondel published a rule that survives in textbooks: twice the rise plus the going should come to roughly 600 to 650 mm, the length of a comfortable stride. Steep stairs are cheap and compact; shallow ones are gentle and cost floor area.
The calculation links the section to the plan. Divide the floor-to-floor height by the rise to get the number of risers, and the plan needs one fewer treads than risers, times the going, in run. Building codes cap the rise and set a minimum going, at limits that differ by country (the caps are of the order of 18 to 22 cm for the rise and 22 to 25 cm for the going; check your own code, these are not design values).
A drawing is a language, and like any language it has conventions so that a stranger can read it. Learn five and most plans open up.
| You see | It means |
|---|---|
| Thick solid line or solid fill | Something cut by the slice, usually a wall (the filled shape is called poché) |
| Thinner line | Something seen below the cut, such as a floor edge or a step |
| Dashed line | Something above or hidden, such as a beam or an overhang |
| A thin arc from a gap | A door and the way it swings |
| A line of rungs with an arrow | A stair, and the arrow points up |
| A dimension string with ticks | Measured lengths, to a wall face or a centre line |
| A north arrow and a scale bar | Which way is up, and how big it is |
This is the same grammar you saw in Form, Space & Order (34/89), where you moved a plan cut up and down and watched windows and doors appear. Line weight is the most useful single habit: heavy for what is cut, medium for what is beyond, light for everything else. A drawing with one thickness of line is hard to read in the same way that a page with one size of type is.
Ivan Sutherland's Sketchpad (1963) let a person draw on a screen with a light pen, and every later CAD program descends from it. For buildings the large step was building information modelling (BIM): instead of a stack of separate drawings that have to be kept consistent by hand, you build one three-dimensional model of walls, doors and floors, each carrying data (material, fire rating, cost), and the plans, sections and schedules are views cut from it. Change a wall's position and every drawing updates. The open file format IFC is standardised as ISO 16739 so that different programs can share such a model.
Two cautions. First, drawings still matter, because the construction documents (not the model) are what a contract refers to in many places, and a model is only as good as the person who put things in it. Second, a rendering, the glossy image from the model, is persuasion, not evidence: it shows the best light, the best day and no wires. An architect learns to ask of every image what the camera and the choices left out. That habit applies to the news and to advertising, too.
Architects draw to think, to test and to tell. Plans, sections and elevations are parallel projections that answer one question each and keep lengths true; axonometrics and perspectives trade measurability for a picture. Scale is a ratio that a graphic bar keeps honest, the section is where height is decided, and a model is a database that drawings are cut from.
Try this: draw the plan of your own room, to scale, on a sheet of paper at 1:50 (every metre becomes 20 mm). Then draw a section through the room's tallest wall. Which one found a problem the other hid?
Sources. Yingzao Fashi (Li Jie, published 1103; second edition 1145): Wikipedia and Cambridge Architectural History summaries. Brunelleschi's perspective demonstration (c. 1415, via Manetti's biography) and Alberti, De pictura (1435): standard art-history accounts. Choisy, Histoire de l'architecture (1899). Blondel's stair formula (Cours d'architecture, 1675 onwards): standard architectural handbooks. Sutherland, Sketchpad (MIT, 1963). IFC is ISO 16739 (buildingSMART). ISO 216 paper sizes. Ching, Architectural Graphics 7th edition (Wiley, 2023; ISBN 9781394206247). Stair limits vary by national code; the ranges here are illustrative. Numbers computed in node: the projections and foreshortening factors (isometric 0.8165), the perspective lengths, the scale-fit table and the stair geometry.