Stairs

Most of architecture can be looked at; a stair has to be used. Every step is a small contract between the building and the body: the height it asks us to lift the foot, the depth it offers to put it down, and the rhythm those two measures impose when repeated twenty times. Get them wrong by two or three centimetres and a stair becomes tiring, unsafe or absurd, however fine its balusters. That is why stairs have attracted some of the most precise and durable rules in the whole of architecture. Unlike most rules in this book, they are still enforced by law.

The vocabulary is simple. The vertical face of a step, and its height, is the riser; the horizontal distance from the edge of one step to the edge of the next is the going (the tread is the board you stand on, which may overhang the step below by a nosing). A sequence of steps without a break is a flight, and the level platform between flights is a landing. The ratio of riser to going fixes the pitch of the stair, the angle of the line joining the nosings.

Two risers and a going

The fundamental rule was stated by François Blondel, first director of the French Royal Academy of Architecture, in his Cours d’architecture (1675–83). Blondel observed that a man walking on the level takes a pace of about two French feet (24 pouces, about 65 cm) and that lifting the foot costs roughly twice the effort of carrying it forward. It follows that a comfortable step should satisfy a simple equation: twice the riser plus the going equals one pace (Two risers and a going make a pace).

℟Two risers and a going make a pace

Proportion every step so that twice its height plus its depth equals the length of a natural pace on the level: two feet, or 24 pouces.

2 r + g = 24 pouces ≈ 65 cm (modern practice: 60–66 cm)

The equation does not fix a single stair but a family of them. A garden flight with low risers must have deep treads; a service stair with high risers must have shallow ones. The table gives some pairs that satisfy the rule, and the figure at the head of the chapter will test any other pair. The same idea, with the pace set between about 55 and 70 cm and limits on the riser and pitch, appears in the building regulations of most European countries today; a comfortable domestic stair usually has a riser of 16–18 cm and a going of 27–30 cm.

Ancient and Renaissance rules

Blondel was not the first to give numbers. Vitruvius, describing the steps in front of a temple, asks that their risers be no more than ten inches and no less than nine, and their treads between a foot and a half and two feet; and he adds that the number of steps should be odd, so that one who begins with the right foot will also set the right foot first on the top (An odd number of steps). The first rule describes a rather steep and ceremonious flight, suited to a raised podium; the second is augury, but it records the sense that a flight is walked as a rhythm with a beginning and an end.

℟An odd number of steps

Give the flight of steps before a temple an odd number, so that one who starts with the right foot will also set the right foot first on the top.

Palladio devotes a chapter of his first book to stairs (Palladio on stairs). He asks for three things: a clear and handsome opening at the foot, so that the stair is easily found; windows along its length, so that it is well lit; and a landing at the top from which the principal rooms open. His limits for the steps (risers of four to six Vicentine inches, treads of one to one and a half feet) give, in modern terms, risers of about 12 to 17 cm and goings of 35 cm or more: easy stairs by any standard. Palladio also warns that stairs must be placed so as not to spoil the rooms, a problem he solved in his villas by tucking narrow stairs into the thickness between rooms, leaving the great external flights to carry the ceremony.

℟Palladio on stairs

Place the stair where it does not spoil the rooms and yet is easily found; light it well; and make the steps no higher than half a foot and the treads at least a foot deep.

riser ≤ ½ ft (≈ 17 cm); going ≥ 1 ft (≈ 35 cm) in Vicentine feet

Straight, returning and winding

Palladio classifies stairs by their plan. A straight stair rises in one or more flights in the same direction; it is the simplest to build and to use, but needs a long run of space. A dog-leg stair turns back on itself at a half landing, so that it fits in a compact rectangle and brings the traveller back above the starting point. A winding stair (Palladio calls it a lumaca, “like a snail”) turns round a central post, the newel, or round an open well, and may be circular or oval.

Winding stairs pose a special problem because their steps taper. Near the newel the treads are too short to stand on; near the outer wall they are unnecessarily deep. The comfortable going is found only along the walking line, the path that people naturally take, a little outside the middle of the flight, and it is there that Blondel’s rule should be applied (The winding stair). Tapering steps used to turn a corner in an otherwise straight stair are called winders, and codes limit them for the same reason.

℟The winding stair

Where space is short, wind the stair round a newel or an open well; measure the going on the walking line, about halfway along the tread, where it should be as generous as on a straight flight.

Palladio admired one winding stair above all: the double spiral at the château of Chambord in the Loire valley (begun 1519), two interlaced flights round a hollow core, so arranged that one person can go up and another come down without meeting. It is often attributed to the influence of Leonardo da Vinci, who spent his last years nearby and drew double spirals, though there is no document to prove it.

Balusters, rails and safety

A stair also needs something to hold. The baluster, a short turned post swelling like a vase, was a Renaissance invention, first used in the late fifteenth century and soon standard on stairs, terraces and roofs; a row of them carrying a rail is a balustrade. Its height and spacing have been fixed by experience and then by regulation: a handrail at about 90 cm above the nosings, gaps too narrow for a child’s head. The figures in this chapter draw balusters at every step, as grand classical stairs usually did.

The other safety rules are just as bodily. Every step in a flight should be the same, because the foot learns the rhythm after two or three steps and stumbles if it changes; a variation of a centimetre is enough to trip people, as studies of accidents confirm. There should be headroom of about two metres everywhere above the pitch line, and landings where a flight turns or grows long. None of this is new: medieval masons set out newel stairs with templates so that every step was identical, and the rhythm of equal steps is what Blondel’s rule is ultimately about.

The grand stair

For most of the Middle Ages the stair was a necessity to be hidden: a spiral in a turret, a steep flight against a wall. The Renaissance began to change this. Michelangelo’s stair in the vestibule of the Laurentian Library in Florence (designed 1520s, built 1559) fills a tall, narrow room with three flights whose central steps curve outward and seem to flow down from the reading room above; it is less a way up than a piece of sculpture about going up. In the villas of the Veneto the external flight to the portico became part of the architecture of arrival, lifting the owner’s rooms onto their basement (The principal floor raised on a basement).

The Baroque turned the stair into the principal room of the palace. A visitor of rank was met at its foot or its head according to status, and the ascent itself became a ceremony staged in a lofty hall lit from above. The imperial stair (one broad flight rising to a landing, then dividing into two flights that return on either side) gave a symmetrical, processional climb with a dramatic turn in the middle (The imperial stair). It appeared at the Escorial in Spain in the 1570s and reached its climax in the German palaces of the eighteenth century, above all Balthasar Neumann’s stair hall at the Würzburg Residenz, covered by a single vast vault painted by Giambattista Tiepolo in 1752–53 with the four continents paying homage to the prince-bishop.

℟The imperial stair

Make the stair of a palace a processional space: one broad flight rising to a landing, then turning back in two flights either side to arrive at the principal floor beneath a single great vault.

Grand stairs almost always use low risers and deep goings: the pace is kept, but it is slowed, and the body is made to rise with dignity rather than climb. The nineteenth century inherited the idea and gave it to the public. Charles Garnier’s grand staircase in the Paris Opéra (1861–75) is a theatre in its own right, with balconies from which the audience could watch itself arrive; the Beaux-Arts museums and railway stations of Europe and America made the perron, the broad flight of steps, the threshold of civic life.

Measure and meaning

Stairs show, perhaps better than any other element, how a rule can be both practical and expressive. Blondel’s equation is a piece of ergonomics three centuries before the word existed, and it is honoured every time a building inspector measures a flight. Yet within its limits the designer has great freedom: a shallow, wide stair speaks of leisure and ceremony, a steep narrow one of service and haste, a spiral of economy or of mystery. The same numbers that keep us from tripping also tell us, as we climb, what kind of building we are in.