planning and designing a stair cases
The various principles to be observed while planning and designing a stair cases are:
1. Step proportions: The riser and tread of each should be a uniform dimensions throughout the length of the stair. The proportion between going and rise of a stop should carefully work out so as to provide comfort and ease to the users.
It should be noted that the rules given above only act as guide but the actual dimensions of going and rise depend upon the space available, height of the building and layout of the stair.
2. Pitch of the stair: The pitch or slope of the stair should neither be more than 40° nor less than 25° for comfortable ascend and descend by the users.
3. Width of the stair: The width of a stair should be such that a person going up can pass a person coming down without any difficulty. The minimum width of stair in a residential building should be 1m, whereas in case of a public building a minimum width of 1.5m is desirable.
4. Length of flight: The number of steps in a flight should not be more than 12 otherwise it becomes difficult to move up and down the flight. The minimum number of steps in flight should be 3.
5. Width of landing: The width of landing should not be less than the minimum recommended width of the stair.
6. Head room: An adequate head room must be provided. It should not be less than 2.13m vertically or 1.5m at right angles to the line of nosing.
7. Winders: They should be avoided as far as possible because they are liable to dangerous and involve extra expenditure in construction. Winders are difficult to be carpeted and are especially unsuitable for public buildings. However they are to be provided when the area of the staircase is limited. In such cases, winders should be placed at the lower end of a flight. In a quarter spaces i.e. 90° turn, only three winders should be provided.
8. Hand rails and balustrades: A stair should be provided with a hand rail along with balustrade to provide assistance, comfort and safety to the users. The height of the hand rail should neither be more than 0.85m and nor less than 0.75m.
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9. Materials: The stairs should be constructed of sound materials of fire-resisting quality. It should be constructed of R.C.C according to building bye-laws being followed in the locality.
10. Location: The stair case should be located in such a position that it can be easily and quickly approachable. A central position in a building would be ideal. It should be so located that sufficient light and ventilation is ensured specially at turning points in the stair case. In a residential building, the stair should be located near the main entrance and screened from outside for privacy. In public buildings, it should be preferably be located near the main entrance.
Classify the stairs according to their layout? Also discuss their suitability?
According to the layout, the stairs are classified as:
1. Straight flight stairs: The stairs which rises from one floor to another in one direction is known as straight flight stair or simply straight stair. This type of stair may be constructed with or without landing.
Suitability: This type of stair is only suitable for a long and narrow stair case.
2. Quarter turn stairs: The stair which turns through 90° either to the left or to the right is known as quarter turn stairs. This type of stairs may be provided either with winders or quarter space landing.
Suitability: This type of stair is suitable where the width of stair case is not more but it has got limited length.
3. Half turn stair: The stair which turns through 180° is known as half turn stair. In such stairs the adjacent flights are in opposite directions separately by half-space landings, two sets of winders or two quarter space landings, according to the space available.
i. Dog-legged stair: A half turn stair with no space between its flights is known as dog-legged stair.
Suitability: This type of stair is suitable where the width of the stair case is limited and is commonly used for single or double storeyed modern buildings.
ii. Open well stair: A half turn stair with a space between its flights is known as open well stair. This stair is also known as an open newel stair when the well left between the flights is of rectangular shape. If the space for this type of stair is limited, a short flight is introduced on the narrow side of the well with two quarter space landings.
Suitability: This type of stair is suitable for multi-storeyed buildings the well allows natural lighting from the top opening.
4. Geometrical stair: A half turn stair in which the well is of curved shape between the forward and backward flights is called geometrical stair. In this type of stair, the change in direction is obtained by winders. It provides easy turning but is tiresome as it is generally without landing.
Suitability: This type of stair is suitable for single or double storeyed buildings.
5. Circular stair: The stair provided in circular stair case is called circular stair. In this type of stair, the strings and the hand rails are continuous and the change in the direction is obtained by winders. All the steps may be supported by a newel at the centre or there may be a circular well hole.
Suitability: This type of stair is suitable when a limited space is available for the stair case. Iron spiral stairs are very suitable for back door entrance as they occupy very little space.
6. Bifurcating stair: The stair having its bottom flight wide which is divided into two narrow flights at the landing at right angles in the opposite directions is called bifurcating stairs.
Suitability: This type of stair is suitable for public buildings, assembly halls, railway foot bridges etc.