STAIRS

A stair is a set of steps leading from one floor to other. It is provided to afford the means of ascent and descent between the various floors of a building .

The room or enclosure of the building in which the stair is located is known as staircase.

The opening or space occupied by the stair is known as stairway.

Stairs may be constructed of timber ,bricks , stone or reinforced cement concrete.

It must be designed to carry certain loads , which are similar to those used for the design of floor.

TECHNICAL TERMS

STEP- It is a portion of stair which permits ascent or descent. It is comprised of a tread and a riser.

THREAD- It is the upper horizontal portion of a step upon which the foot is placed while ascending or descending .

RISER-It is the vertical portion of a step providing a support to the tread.

FLIGHT-It is the unbroken series of steps between landings.

LANDING- It is the level platform at the top or bottom of a flight between the floors. A landing facilitates change of direction and provides an opportunity for taking rest during the use of the stair.

RISE-It is the vertical distance between two successive tread faces.GOING- It is the horizontal distance between two successive riser faces.NOSING- It is the projecting part of the tread beyond the face of the riser .It is usually rounded off from architectural considerations.SCOTIA-It is moulding provided under the nosing to improve the elevation of the step, and to provide strength to nosing.SOFFIT-It is the underside of a stair.PITCH OR SLOPE-It is angle which the line of nosing of the stair makes with the horizontal.STRINGS OR STRINGERS-These are the sloping members which support the steps in a stair .They run along the slope of the stair.NEWEL POST-Newel post is a vertical member which is placed at the ends of flights to connect the ends of strings and hand rails.BALUSTER-It is a vertical member of wood or metal, supporting the hand railBALUSTRADE-It consists of a row of balusters surmounted by a hand rail, to provide protection for the users of the stairs .HAND RAIL-It is a rounded or moulded member of wood or metal following generally the contour of the nosing line, and fixed on the top of balusterHEAD ROOM-It is the minimum clear vertical distance between the tread and overhead structure .RUN-It is the total length of stairs in a horizontal plane,including landings.

REQUIREMENTS OF GOOD STAIRS

LOCATION:It should be so located as to provide easy access to the occupants of the building .It should be so located that it is well lighted and ventilated directly from the exterior.It should be so located as to have approaches convenient and spacious .

WIDTH OF STAIR:It should be wide enough to carry the user without much crowd or inconvenience. In a domestic building , a 90 cm wide stair is sufficient while in public building 1.5 to 1.8 m width may be required.

LENGTH OF FLIGHT:From comfort point view, the number of steps are not more than 12 and not less then 3 .

HEAD ROOM:The clear distance between the tread and soffit of the flight immediately above it should not be less than 2.1 to 2.3 m ,so even that a tall person can use the stair with some luggage on his head .

BALUSTRAD:Open well stair should always be provided with balustrade, to provide safety to the users.

STEP DIMENSION:The rise and going should be of such dimensions as to provide comfort to the users .The going should not be less than 25 cm , though 30cm going is quite comfortable. The rise should be between 10cm to 15cm.The width of landing should not be less than the width of stair.

CLASSIFICATION OF STAIRS

STAIRS

STRAIGHT STAIRS

TURNING STAIRS

QUARTER TURN

STAIRS

HALF TURN

THREE-QUARTER

TURN

BIFURCATED

CONTINIOUS

Each of turning stairs are classified into 3 types,1.Newel stairs2.Well or open newel stairs3.Geometrical stairs

Newel stairs- It is the one which has a newel at the foot and head of each flight of the stair.

Well or open stairs- Lateral space is left between the turning flights. Open newel stairs give best appearances and are strong.

Geometrical stairs- They have continuous strings and hand rails and are set out in accordance with geometrical principles.

STRAIGHT STAIRS

In this type, this stair runs straight between the two floors. It is used for small houses where there are restrictions in available width. The stair may consist of either one single flight or more than one flight with a landing.

TURNING STAIRS

QUARTER TURN STAIRS-

A quarter turn stair is the one which changes its direction either to the left or to the right, the turn being affected either by introducing a quarter space landing or by providing winders.

There are two types-

1-Newel quarter turn stairs-These stairs have the conspicuous newel posts at the beginning and end of each flight. At the quarter turn there may either be quarter space landing or there may be winders.

2-Geometrical quarter turn stairs- Here the stringer as well as the hand rail is continuous, with no newel post at the landing.

HALF TURN STAIRS- Half turn stairs is the one which has its direction

reversed or changed for 180˚.

There are 3 types here-

1-DOG LEGGED STAIRS-

This name is given because of its appearance in sectional elevation. Newel posts are provided at the beginning and end of each flight.

2- Open newel half turn stairs-

Open well or open newel half turn stair has a space or well between the outer strings .The space between the two strings may vary from 15cm to 100cm

3-Geometrical half turn stairs-

The essential features of such stairs are that the stringers and hand rails are continuous, without any intervening newel post .This may be either with half space landing or without landing

THREE QUARTER TURN STAIRS - A three quarter turn stairs has its direction changed three times with its upper flight crossing the bottom one . It may be either newel type or open newel type.Such type of stair is used when the length of the stair room is limited and when the distance between the two floors is quite large.BIFURCATED STAIRS - This type of stair has a wider flight at the bottom which bifurcates into two narrower flights, one turning to the left and the other to the right at the landing.

CONTINIOUS STAIRS- Continuous stairs are those which don’t have any landing nor any intermediate newel post .They are geometrical in shape. They are of 3 types -

1) CIRCULAR STAIRS-

Circular stairs don’t have a central pole and there are hand rails on both sides.

2) SPIRAL STAIRS-

These stairs are usually employed at locations where there are space limitations. They are also used as emergency stairs, and are provided at backside of a building. These stairs are not comfortable to use.

3) HELICAL STAIRS-

These looks very fine but its structural design and construction is very complicated .It is made of RCC in which a large portion of steel is required to resist bending, shear and torsion .

STAIRS OF DIFFERENT MATERIALS

Stairs may be constructed of following materials:-

1)Timber

2)Stone

3) Bricks

4)Steel

5)R.C.C

1) Timber stairs-

These stairs are light in weight and easy to construct, but they have very poor fire resistance.They are used only for small rise residential buildings.The timber used for the construction should be free from fungal decay and insect attack, and should be well treated before use.Mostly mahogany or oak is used.

2) Stone stairs-

Stone stairs are widely used at places where ashlar stone is readily available.Stone stairs are quite strong and rigid, though they are very heavy .Stone used for the construction of stairs should be hard , strong and resistant to wear . Stones are fire resistant also .

3) Brick stairs-

Brick stairs not very common, except at the entrance.The stair consists of solid wall or arched openings for obtaining storage spaceBrick steps need frequent maintenance.

4) Metal stairs-

Stairs of mild steel or cast iron are used only as emergency stairs .They are not common in residential and public buildings, though they are strong and fire resistant .This is because they are not good looking and they make lot of noise when used by users.

5) R.C.C stairs-

R.C.C. Stairs are the one which are widely used for residential, public and industrial building.They are strong, hard wearing and fire resistant.Steel reinforcement is used to resist bending moments, shear force and torsional moment.

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