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Encyclopedia Britannica - Main :: SOU-STE |
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STAIRCASE , the term usually applied (Fr. cage d'escalier, Ger. Treppenhaus) to the stairs leading to the upper floors in a building, including the enclosure walls. In the ordinary house a single staircase only is provided; in larger ones a second or service staircase; in those of more importance, especially where the principal reception rooms are on the first floor, a grand staircase leading to the latter, and other subsidiary stairs or staircases. Architecture.Among the earliest examples are those found in Egypt, generally built in the thickness of the walls, as in the pylons and temples; a remarkable example was found by Dr Arthur Evans in Cnossus, in Crete, consisting of a staircase in stone, 6 ft. wide, with return flights of stairs, rising through two floors; the staircase in the temple of Zeus at Olympia leading to the gallery, is supposed to have been in wood, but in some of the Greek temples have been found stairs in stone with return flights. In the Tabularium at Rome there is a long flight of 67 steps leading up from the Forum to a hall
hall
Construction.The primary object of stairs, in house-building, is to afford a safe and easy communication between floors at different levels. To make the communication easy the " rise " and width (or " tread ") of the steps should be regular and suitably proportioned to each other with convenient landings; there should be no winding steps, and the rail which is fixed to render the use of the staircase safe should be strongly fixed with its top at a convenient height for the hand. The first person that attempted to fix the relation between the height and width of a step upon correct principles was, we believe, Blondel, in his Cours d'architecture. His formula is applicable to very large buildings but not to ordinary dwellings. Ashpitel, who investigated the subject at length (in Handrails and Staircases), gives the following rules for different proportions of treads and risers Width of tread Height of rise in inches. in inches. 12 51 III 5: II 6 101 6; lo 61 9I 6s 9 These dimensions give angles of ascent varying from 24 to 37. The projection of the nosings is not reckoned in the width of the treads and must be added to determine the full width of the treads. It will be seen upon examination that these proportions may be expressed in the following simple formula: 23 = twice the rise in inches + the tread in inches. An American rule is to make the sum of the rise and tread equal to 17 or 171 in. The forms of staircases are various, the simplest being a straight flight, which type should only be used to a low storey. In towns, where space cannot be allowed for convenient forms, they are often made angular, circular or elliptical, with winding steps, or are constructed of composite form partly straight and partly circular. In large buildings, where convenience and beauty are the chief
Besides the straight flight of stairs, stairs may be designed in almost numberless different ways to suit the position which they are to' occupy or with a view to architectural effect, but whatever position or form they are made to take their chief
dog-legged or newel stair, open newel stair, geometrical stair, circular newel stairs (see fig. I). rWW '' +ti .;a Straight Goa FIG. I. The newel or dog-legged stair is so termed from its supposed resemblance to a dog's hind leg. In this form the staircase is divided in width into two equal parts and the outer string
Open newel stairs, as in the previous example, have newels placed at the angles, but are so arranged as to enclose a well. This is more convenient for the distribution of light than the dog-legged stairs, especially when the lighting is effected by means of a lantern sky-light placed at the top of the staircase. Geometrical Stairs usually enclose a well, which may vary very much in size and shape from merely a narrow slit between the flights to a square opening admitting of ample ventilation and lighting. This form has continuous strings and handrail, and may be rectangular, circular or elliptical in plan, although it is especially adapted for the curved forms and most satisfactory when so treated. Such stairs are more difficult to construct than the newel stairs already mentioned and lack their strength, as in the absence of the strong framed newel posts the handrail depends for support entirely upon the balusters, which must therefore be very securely fastened to the treads. When wood balusters for the most part are used bars of iron are often introduced at intervals to afford additional stiffness. Circular geometrical stairs are built on a circular plan around a well. Each step is necessarily a winder radiating from the outer string
wall
wall
Solid newel or spiral stairs are circular or polygonal on plan and built around a central pillar or newel, which may be square, polygonal or circular in section. This also is a form of stair-building especially suitable for erection in stone, the central newel being formed on the step itself, and the other end well pinned into the masonry of the wall. Each succeeding step should be dowelled at the newel to the one below and should lap for a matter of two or three inches at least for its entire length over the one below and in this way obtain extra support. The newel stair was at its best in Elizabethan and later Renaissance times. The older form of staircase with circular newel and narrow winding steps was found ill adapted to the altered conditions when convenience and elegance were becoming more sought after. The designers of this period found in the open newel stair a construction capable of being developed into a dignified and beautiful feature of domestic architecture, and they certainly brought out its possibilities in a remarkable manner. This is evidenced by the many fine examples, handed down to us by the architects of the Tudor period, to be found in the great mansions which date back to the time of the early Renaissance. Steps were arranged in broad short flights with wide treads and easy rise. Landings were freely used, and in many cases were large enough to be used as galleries for the display of pictures. The work was generally solidly executed in oak, and carved and moulded decoration was lavished upon every detail. The newels, much enriched, were frequently carried up to the ceiling and formed a portion of the arcading which was often a prominent feature around the well. In the period of the later Renaissance the newel principle of construction was still retained and the main features were the same, but they were planned with longer flights and the manner of decoration partook of a more severely classic nature. One of the first examples is that of the Chateau de Blois, and of modern treatment that of the Grand Opera House, Paris. In the period of the Georgian era the geometrical staircase was much'favoured and very generally used in domestic buildings. Although more difficult to build it must be admitted that this type of stair is not so satisfactory in a number of ways as the newel form. With its continuous curving strings and handrail it has a certain elegance of its own, but in principle of construction it is not so good, nor can it compete with the open newel stair in regard to the ease with which the latter lends itself to schemes of artistic decoration. As before remarked, however, it is well adapted for stairs circular and elliptical in plan. Experience has proved concrete to have fire-resisting properties of the most effective character, and it does not possess the propensi- o,,d ties for splitting concrete and flying under and stone the action of stairs. heat that belong to stone. Steel or iron is often employed as an additional support for stone and concrete stairs. In the case of concrete work iron bars are frequently embedded in the steps for their full length, and are in this way hidden from sight while at the same time serving the purposes of support. When a more ornate appearance is desired than is obtained by the use of plain concrete the steps may be encased in other material to secure a richer effect. Marbles
Dogiegged hole ,paw Open Newel Carder Geometrical None stirs - epnciril aedan ' 'STAIRCASE 765 step may be divided into several different parts such as the tread, the riser and the nosing. The tread is the horizontal
Rise, the vertical distance between the surface of one tread and that of the next. Going, the horizontal
Newels, strong posts occurring at intervals in a newel staircase. They are placed at the ends of flights where junction is made to landings, at turnings, and at the top and bottom of the staircase. They should be strongly framed in the stair construction, and have the string and handrail housed into them. Newels are sometimes of iron, and in large stone staircases of stone. They are sometimes of elaborate form and often designed as a pedestal carrying a lamp or statuette, or they may be carried up to form part of some ornamental framing around the staircase. In America the newel is the main post where the stairs begin, and the remainder of the posts used in the framing are termed angle posts. Handrail.This is a rail commonly of hard wood which runs up at the same slope as the stairs at a height above the nosing line of about 2 ft. 8 in. (that is 3 ft. minus half a rise) to the upper surface of the rail. On the level, such as on landings, it is usually fixed 3 ft. above the surface. These are the heights at which a handrail is found to give most assistance to persons going up or down stairs. Handrails are made in other materials such as iron and bronze. A handrail is generally upheld by balusters, which are vertical bars or posts filling in the space between the handrail and the string or the treads. They are made in many shapes and in many different materials such as wood, iron, bronze, stone and marble. Sometimes in the place of balusters the space usually occupied by them is filled in with scrollwork of wrought or cast iron or bronze, or with panels of wood perforated, perhaps, and richly carved. Core-rail.An iron band is frequently used in geometrical stairs to give extra strength and stiffness to the handrail. It is generally about ; in. thick, being screwed into a groove formed in the under-side of the handrail. It is especially necessary for the curved portions of the handrail, where the grain of the wood is often cut across. String.Strings are the members that carry the treads and risers which in wood stairs are housed into them or else fitted into notches cut in the strings to receive them. In the former case the supporting member is termed a close string, but if notched out for the steps it is known as a cut string (see details, fig. 4). A cut and mitred string is similar to this last, but has the vertical cut of each notch splayed and the riser is mitred to it so as not to show the joint. Strings are either wall strings or outer strings; the former are fixed against the wall, the latter run up from newel to newel or in geometrical stairs ramp and curve according to the nosing line. Rough strings or rough carriages are placed between the inner and outer 'strings to afford additional support to the treads and risers, and rough brackets about in. thick are fitted into the steps and spiked to the carriages. Ramp.This is a concave curve formed in one plane when changing the direction of the handrail or string. In America it is known as an easing. Knee.This is a convex curve in one direction. When used in conjunction with a ramp it forms a swan-neck, which is a combination of ramp and knee. WreathThis is a curve formed both horizontally and vertically in the handrail or string. It is often necessary in geometrical stairs where a change of direction takes place. Although more in the nature of a mechanical lift or elevator than a stair, moving stairways may perhaps find a place in this article owing to their resemblance and to the fact that their Mving object is to convey the passenger quickly and easily in oclines. to a higher level without the necessity of a tedious climb up stairs, or of a wait such as is often entailed with a vertical lift. The contrivance consists of an endless inclined platform formed of links bolted together, which allow it to travel round wheels fixed at the top and bottom of the stairway and hidden within its framing. This is kept in continual motion by mechanical means, usually by an electric motor, which causes it to travel at the rate of about too ft. a minute. The handrail also moves at the same rate, so that a passenger merely stepson to the lower portion of the stair, places his hand upon the handrail, and is carried swiftly and safely up to the next floor, where he is deposited without any effort on his part. The process of stepping on and getting off the stairway is amazingly simple and without any element of danger pttrpose. Stairs of fine concrete to which is given the name of obtain a regular sweep up from the bottom to the top step. Each artificial stone " have largely superseded those constructed of genuine stone. It is very strong and capable of being further fortified by the introduction of steel core bars without detriment to its appearance; it is consistent in quality and special shapes are readily moulded; it is very hard-wearing, especially when the aggregate consists of a hard nature such as granite chippings. The stairs are built by pinning each step in the wall either at one or at both ends. In the first case they are termed cantilever or hanging steps, and it is advisable to use steel reinforcement and pin the end of the step at least 9 in. into the wall. When fixed at both ends the pinning need not be so deep, and unless the stairs are very wide the steel core may be omitted. The steps are either rectangular or spandrel-shaped in section (figs. 2 and 3); the former are stronger and easier to fix than the latter, which, however, give a better appearance and can be finished with a plain smooth soffitt. Iron balusters are generally used for stone and concrete staircases, and are fitted with lug terminations which are let into dovetailed mortices formed in the top or side of the stair tread and held fast by molten lead, neat Portland cement, or a mixture of sulphur and sand. The construction of wood staircases forms a special branch of the joinery craft, and many books have been written on the subject. Numerous methods of setting out the handrails have Staireasing been put forward by different authors, among them and Hand- being the tangent system, which gives excellent results ratting. at perhaps the smallest cost compatible with good work. It is noteworthy that the common practice in England with regard to wood stairs is to frame and form the finished work in the workshop and fix it bodily in the position it has to occupy. In America, especially in the eastern states, the finished staircase is built up piece by piece upon a rough framework which has been used by the workmen during the erection of the carcase of the building. In many instances the strings consist of easings and panellings nailed upon the rough skeleton work. Stairs are built in many kinds of materials, such as wood, stone, concrete, iron and brick. Often two or more kinds of materials are used in the same staircase, as when constructions of concrete or stone are reinforced with iron or steel. It is common also to fit to a staircase handrails, balusters and newels of a different nature from the steps themselves. The spandrel or triangular-shaped space between a flight of stairs and the floor is frequently enclosed with wood-panelled framing and fitted with a door so that it may be made use of for cupboard accommodation. There are a number of technical terms connected with staircases which require some explanation to enable the drawings to be easily understood: Staircase.This comprises the whole of the stair construction and is the name given to the space or enclosure which contains the stairs. Well-hole, the open space enclosed by the stairs. Flight, a continuous series of steps between two landings. Landing, a platform forming a kind of halting-place between two flights of stairs. A quarter-space landing forms a space, usually a rectangle, equal in width and length to the breadth of the two flights which it separates. A half-space landing extends the total width of the staircase. Flier.Fliers are steps that have the nosings of the treads parallel one to another. Winder.This is an angular-shaped step. A winder fitted into a wall angle is often termed a kite winder, from the fact that it resembles a kite. In planning stairs the width of the winder tread at a distance of i8 or 20 in. from the handrail should equal the width of a flier. Curtail Step.This may be either a flier or a winder. One or both ends of the step are projected to form a base for the newel and are shaped to a scroll which often follows the line of the curve terminating the handrail. It is usually the step or steps at the base of a staircase that are formed in this way. Bull-nosed step, one having a blunt rounded end. It may be shaped to a quarter or half circle. Dancing Stairs.The introduction of winders in geometrical staircases brings about awkward complications in the curve of the handrail and strings, for the width of the winding steps at the hand-rail being much less than that of the fliers, while at the same time the rise is necessarily equal, causes an unsightly knee in the handrail and in the strings. To obviate this the whole of the steps are made to dance, that is, they are all shaped as winders in order to divide the going equally between them and thus obtain a regular slope for the strings and handrail. Often the first and last three or four steps of a flight are made ordinary fliers. In a polygonal or elliptical staircase the whole of the flight is constructed in this way so as to to the passenger. For high buildings, underground railways and similar positions, a spiral form is used which winds round in a circular shaft to the highest level and returns in the opposite direction in a similar manner, taking up and setting down passengers as it revolves. Although this type of elevator is probably not so rapid as the vertical lift working in a straight line to the point it is desired to reach, its great advantage is that it does away with the waiting which often causes so much annoyance with ordinary lifts. The by-laws of the London County Council contain many stipulations regulating the construction of staircases, and these are summar-Lew. ized below. In every public or other building of more than 125,000 cub. ft. constructed to be used as a dwelling for separate families the floors of lobbies, corridors, passages, landings, and also the flights of stairs, shall be of fire-resisting materials. The principal staircase of every dwelling-house shall be ventilated by means of a window or skylight opening directly into the external air. In buildings occupied in separate tenements by more than two families the common staircase shall be ventilated upon each storey above the ground storey by windows or skylights, or otherwise adequately ventilated. Staircases in churches, chapels, public halls, lecture rooms, exhibition rooms and buildings for similar purposes are subject to the following conditions: Stairs shall be supported and enclosed by brick walls at least 9 in. thick. The treads of each flight shall be of uniform width, and stairs, corridors or passages shall be 4 ft. 6 in. wide unless the building is for the accommodation of less than two hundred persons, when it may be 3 ft. 6 in. wide. If for more than four hundred persons the width must increase by 6 in. for each additional hundred persons up to a maximum of 9 ft. Staircases 6 ft. wide and upwards shall be divided by a hand-rail. Two staircases may be substituted for one large one, each to be two-thirds the width required for the single stair, but not less than 3 ft. 6 in. Accommodation upon different levels must be provided with separate stairs leading directly to the street or open. Exit doors must open outwards. Under the theatre regulations dated 1892 the same widths hold good, but the minimum width is increased to 4 ft. 6 in. Every staircase for the use of the audience shall have solid square section steps of approved stone or concrete with treads of uniform width not less than 11 in. wide or rise greater than 6 in. Winders are prohibited, and the flights must have not more than twelve steps nor less than three steps each. Both ends of each step shall be pinned into the wall. The several flights shall be supported and enclosed on all sides by brick walls not less than 9 in. thick carried down to the level of the footings. Not more than two flights of twelve steps each shall be constructed without a turn. Landings to be 6 in. thick, square on plan and supported under the middle by 9 in. brick arches. A continuous handrail supported on strong metal brackets to be fixed on both sides of steps and landings, and if possible chased into the wall to avoid projection. The roof over the staircase shall be of fire-resisting materials. Separate exits are required for different parts of the theatre or hall. The Factory and Workshop Act 1901 contains somewhat similar conditions, but in this case the staircases communicate with each floor and the roof. The minimum width of tread shall be to in. and the maximum rise 7; in. Steps of spandrel section may be used having a thickness of 3 in. at the smallest part for staircases 3 ft. 6 in. wide, and not less than 41 in. thick for staircases 4 ft. 6 in. wide. External fire escape stairs must be constructed with dead bearings and without cantilever work. They must comply with the requirements for enclosed staircases as regards width, going, width of treads, height of risers, doors, handrails, &c. They must deliver at the ground-level into a public way or some large space. Where in general use the treads must be of non-slippery material as distinguished from perforated iron or chequered iron plates. The second schedule of the London Building Act 1894 sets forth the materials that are deemed fire-resisting under the act, and specific in the case of staircases " oak or teak or other hard timber with treads and risers not less than 2 in. thick." The law regulating the construction of buildings in the city of New York
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