Chapter 5 Stair

Building Technology (EG 626 CE)

Er. Suraj Bhattarai 1

Stair Stair is mechanical structure having series of steps

suitably arranged for the purpose of connecting different levels in the building.

It may also be called as the means of vertical transportation in the building.

It is made of various materials, such as; timber, stone, brick, steel concrete etc.

The function of stair is to provide a suitable means for the movement of people from one floor to another and also a way for escape in case of fire and other emergency.


Elements of stair Stairwell/staircase: The space in which the stairs and landings are housed. Tread : The upper surface of a step on which the foot is placed. Riser : The vertical member between two consecutive risers. Step : Riser + Tread Nosing : The exposed edge of the tread. Going : The horizontal distance between two consecutive risers. Rise : The vertical height between consecutive tread. Flight : A series of steps with out a landing. Newel-post: A post forming the juncture of flights of stair with landing or

carrying the lower end of strings. Strings : The member receiving the ends of steps or providing support for

the steps. Strings are usually provided one at the outside and other adjacent to the wall.


Elements of stair Landing : A platform or resting place provided between two flights. It may be

half, quarter or full depending on the span. Scotia : Molding provided under nosing to beautify the elevation of the step. Winders : Tapering steps, which are provided for changing the direction of a stair. Soffit : Under-surface of a stair. Line of nosing: Imaginary line touching the nosing of each step. Slope or pitch: Angle between horizontal line and the line of nosing. Hand rail : Member of stair at the top of baluster and acts as the support of hand of

passerby. Baluster : Vertical member that supports handrail. Balustrade : Frame consisting of balusters and acts as fence or guard to the users of

stair. Head room : Clear vertical distance between the tread of a step and soffit of flight or

ceiling of a landing immediately above. Spandrel : Triangular framing under the outside string of an open string stair.


Typical stair


Newel post

Baluster

Handrail

LandingTread

Rise

String

wall

Details of Stair


Riser

Nosing

Scotia

Going (Tread)

Step

Hand Rails

Ideal requirements of stair Location

easily accessible and well ventilated. For residential building, it should be centrally located. For public building, this should be near to the entrance. For apartment building, stair should be one in the central location and

other by the side of the building for easy escape in case of emergency. Width of stair

Wide enough to carry the users with out much crowd or inconvenience. Minimum width for public and residential building is -150 cm & 100 cm

respectively. Length of flight

Maximum & minimum numbers of steps in a flight be 12 & 3 respectively.


Ideal requirements of stair Slope of stair

It should be just enough to be comfortable to the users. In general, it is taken between 25-40.

Head room Clear space between tread and the soffit of the stair above may be

more than 7ft. or 2.10 m. Material - should be strong & safe. Landing

More than or equal to the width of the flight. Winders

These are the tapering steps to change the direction & avoided as far as possible.


Ideal requirements of stair Step proportions

T + 2R = 60-64 cmT * R = 400-426 cm2T + R = 40-45 cm

Standard values For residential building: T = 22-27 cm, R = 15-17 cm For public building: T = 25-30 cm, R = 10-15 cm

Usual sizes of steps: (RxT) For public buildings ranges from 10x30 cm to15x25 cm For residential building ranges from15x27 to 17x22cm.


Types of staircase Straight stairs

Steps in one direction only, may have one or more flight, access to porch etc.

Quarter-turned L-shaped stair having landing at the corner.

Doglegged Two straight flights running in opposite direction, no space

between flights. Open well (open newel)

Opening is left between two flights of doglegged stair.


Types of staircase Geometrical

Similar to open well, but the space left between flights is curved. Circular

Stair takes the shape of segment of circle. Bifurcated

Wide common flight is bifurcated to two flights with quarter turned landing.

Spiral All steps are radiated from a common newel post.

Helical Spiral stair having well or open space in the middle.


Types of staircase


Straight stair Open-well stairDog-legged stair

Types of staircase


Circular stair Spiral stairBifurcated stair

Geometrical stair

Types of staircase


Helical stair

Plan And elevations


Plan and elevations


Dimension for Stair (IS Code)

Types of bldg. Riser (mm) Tread (mm) Slope Unobstructed width of

stairMin. Opt. Max. Min. Opt

.Max Opt. Max Min. (mm)

Residential 100 175 190 225 250 350 350 400 800

Semi-public(Factory, office,

school, shop)

100 165 190 250 275 350 310 380 1000

Public(cinema, theatre,

stadium, hospitals)

100 150 280 280 300 350 270 330 10001200 for hospitals


Design of stair It is the calculation of number of steps with the

presumption of comfortable access to desired floor. The size of the steps should be assumed in such a way

that the stair can be accommodated in the given space with highest level of comfort.

Stair is the center of focus in building & attention should be given for comfort and aesthetic beauty.


Procedure of design of Stair Given the level difference between two floors (ceiling height plus thickness of floor slab).

Assume the types of building and stair and accordingly the size of riser(R).

Find the number of risers by NR = (level difference/size of riser).

Find the number of treads by NT = (NR - 1). Assume the size of tread (T). Assume the width of the stair. Consider the size of landing (L) equal to width of stair. Assume the entry space (E), generally equal to landing). Find the total length of stair = (NT * T) + L +E. Adjust the size of riser and tread if required.


Example 1.0 Design a dog-legged staircase for a residential

building in a stairwell of 4.5 mX3.0m and vertical span between two floors is 3.0m. Assume the necessary data. Draw a neat sketch to support your desi

Floor height=3000mm (Given) Assuming the ht of rise=150mm No of rise= floor ht/ht of rise=3000/150=20 nos. No of flights in dog-legged stair= 2 nos. No of riser in a flight= total nos. of rise/2=10 nos. Nos. of tread in a flight= nos. of rise in a flight-1=9

nos. Er. Suraj Bhattarai 21

Width of tread= 600-2R=600-2X150=300mm Width of stair=space given as

stairwell/2=3000/2=1500mm Width of landing=width of stair=1500mm Length of stair = tread X nos. of tread in a flight+

width of landing = (300X9+1500) mm = 4200mm, this eventually fits in the space (4.5m) Design conclusion could be illustrated as: As desired it is a dog-legged staircase Width of the staircase is 1.5 m


Width of landing is 1.5 m Rise=150mm and total nos. of R=10X2=20 Tread=300mm and total nos. of T=9X2=18 Total length of staircase is 4.2 m.


2.0 design a dog-legged stair for a building in which floor height is 3.6 m. the stair hall measures 2.5m * 5m. (refer solved example of B.C Punima)

3.0 design a suitable staircase for public building in a hall of size 4.25m * 5.25m. The vertical distance between floor is 3.9m. (soln refer B.C punima)

4.0 a suitable stair has to be located in a staircase 7.62m long, 4.57m wide and 4.57m height with a door 1.22m wide in each of the longitudinal wall. The doors face each other and are located with their centres at a distance of 1m from the respective corners of the staircase. Assuming that it is a public building, design a stair and draw dimensional sketches.


5.3 Ladders, Ramps, Lifts and Escalators Lifts/Elevator For most people residing in urban cities, elevators have

become an integral part of their daily life. Simply stated, an elevator is a hoisting or lowering mechanism, designed to carry passengers or freight, and is equipped with a car and platform that typically moves in fixed guides and serves two or more landings. The elevators can be broadly classified as either electric traction type or hydraulic type


Traction elevators have an elevator car and counterweight attached to opposite ends of hoist ropes. The hoist ropes pass over a driving machine that raises and lowers the car. Traction elevators run on load-bearing rails in the elevator hoistway. Traction elevators are most often used in mid-rise and high-rise buildings with five or more floors.

Hydraulic elevators, on the other hand, are raised by forcing pressurized oil through a valve into a steel cylinder located above ground or underground. The pressure forces a piston to rise, lifting the elevator platform and car enclosure mounted on it. The car is lowered by opening the valve and allowing the weight of the car to force oil from the cylinder in a controlled manner. When the valve is closed the car is stopped. Since the weight of hydraulic elevator cars is borne by the piston, there is no need for a structural framework or load-bearing rails. Hydraulic elevators are commonly found in low-rise buildings with two to five floors.


Types of lifts Passenger lift Goods or service lift Open lift Terminology used in lift Call indicator, Car body work, Suspension ropes, Lift

well, Machine room


A lift shall be provided in all buildings as prescribed hereunder. (i) In case of Building having height more than 13.0 Mts. lift shall be

provided. (ii) Lift shall be provided at the rate of one lift for 20 tenements of all the

floors. or part thereof for residential buildings and at the rate of one lift per 1000.00 sq.mts. or part thereof of built-up area for non-residential buildings. The tenement and built-up area on ground floor and two upper floors shall be excluded in computing the above requirement. Lift shall be provided from ground floor and shall have minimum capacity of six persons. On the basis of detailed calculations based on the relevant provisions of National Building Code, the number of lifts can be varied.

(iii) Not withstanding anything contained in the Development Control Regulations in case of building with 21 meters or more in height at least two lifts shall be provided.



Fig Traction elevator/lift

Hydraulic Elevator


Escalators The other mode of vertical building transportation is Escalator. It can be

described as moving stairs typically used to carry large number of people at high volumes through a limited no of floors. These are commonly used in high density areas or where sudden traffic surges are expected at times; for example at discharge times from offices, railways underground stations, airport terminals, theaters, shopping malls and departmental stores. In such applications, escalators will provide shorter travel time than elevators because elevator cars are limited in size and passengers have to wait longer for the service.

Ramps Ramps both external and internal connect different levels and are essential for

wheelchair users and useful for others such as parents with pushchairs, shoppers with trolleys and some older people. They need to be designed and detailed with care if they are to have real practical value.

Disabled people who are not wheelchair users, and some older people, find ramps particularly long ones inconvenient or difficult, and prefer to use steps. Therefore a ramp should always be associated with steps in close proximity, which should also be carefully designed.


(1) Ramps for pedestrians : (a) General :- The provisions applicable to stairway shall generally apply to

ramps.A ramp in a hospital shall not be less than 2.25 Mts. wide in addition to satisfythe firefighting requirements.

(b) Slope :- A ramp shall have slope of not more than 1:10. itshall be of non-slippery material.

(c) Handrail :- A handrail shall be provided on both the sides of the ramp. (2) Ramps for handicapped people :- The provision of the ramp with a

handrail to every public building on ground floor only as compulsory for handicapped people as per the revised National Building Code.

(3) Ramp for basement or storied parking :- For parking spaces in a basement and upper at least two ramps of adequate width and slope shall be provided preferably at the opposite and such ramps may be permitted in the side and rear marginal open spaces after leaving sufficient space for movement of firefighting equipment.


5.0 StairStairElements of stair Elements of stairTypical stairDetails of StairIdeal requirements of stairIdeal requirements of stairIdeal requirements of stairTypes of staircase Types of staircaseTypes of staircaseTypes of staircaseTypes of staircasePlan And elevationsPlan And elevationsPlan and elevationsDimension for Stair (IS Code)Design of stairProcedure of design of StairExampleSlide Number 22Slide Number 232.0 design a dog-legged stair for a building in which floor height is 3.6 m. the stair hall measures 2.5m * 5m. (refer solved example of B.C Punima)5.3 Ladders, Ramps, Lifts and EscalatorsSlide Number 26Slide Number 27Slide Number 28 Slide Number 30Hydraulic Elevator

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Chapter 5 Stair