Design of Staircase Calculation
Stairs is a set of numbers of the stair which provide easy traveling from floor to floor. The room or space between which a stair is located is known as the staircase. The staircase provides access & communication between floors in multi-story buildings. They are the path by which fire can spread from one floor to another.
Therefore it must be enclosed by fire-resisting walls,¢ floors, ceilings, and doors. It must be designed to carry certain loads, which are similar to those used for the design of the floors. For the construction of stair various materials can be used like Timber, Bricks, Stone, Steel or Reinforced Cement Concrete.
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Design of Staircase Calculation – Technical Terms:
STEP: – It is a portion of the stair which provides upward or downloads movement. A stair is composed of a set of steps.
TREAD: – It is a top portion or surface of step on which foot of ascender or descender comes when going up or download by stair.
RISER: – It is a vertical portion of a step providing support to the tread.
LANDING: – It is a level platform at the top or¢ bottom of a flight between the floors.
RISE:– A vertical Space between the top of lower tread and bottom of upper tread faces.
GOING:- It is a horizontal distance between two successive riser faces.
NOSING:- It is the projected portion of a tread beyond the face of the riser.
SCOTIA:- It is a moulding provided under the nosing to provide strength to the nosing.
SOFFIT:- it is a portion which is the underside of stair.
PITCH OR SLOPE:- It is the angle which the line of the nosing of the stair makes with the horizontal.
FLIGHT:- This is an unbroken series of steps between landings.
STRINGS OR STRINGERS: – These are the slopping members who support the steps in a stair.
NEWEL POST: – It is Vertical member of the stair which is located at end to each flight to connect the ends of strings and handrail.
BALUSTER: – It is a safety member of the stair which is made of wood or metal, supporting the handrail.
HEADROOM: – It is the clear vertical distances¢ between the tread and overload structure.
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An important point to Consider while calculating Rise and Tread:
Before starting please make the below assumptions
- The minimum height of the riser is 6” inches.
- The minimum tread width is 9” inches.
(Note – This is not a fixed rule, according to the type of building, use of the building and many other factors affect the size of the rise and tread for stair.)
For Example, in hospitals, the rise maybe 5″ because the staircase mostly utilized only by the ill or sick people where they have to climb without using their full energy. So the riser may be shortened for easy access. The tread also should be wider enough.
The reason we are providing 10” inches for tread is every person will wear a slipper which may be maximum 10” for an average adult person based on that we are making tread space as 10” inches minimum.
General Guidelines for Planning Staircase:
The following are some pointers to be considered while planning a staircase:
• The respective dimensions of tread and riser for all the parallel steps should be the same in the consecutive floor of a building.
• The minimum vertical space or headroom above any step or the stair should be 2 m.
• Generally, the number of risers in a flight should be restricted to 12.
• The width of the stair should not be less than 850 mm. The standard width of any stair may be between 1.1 to 1.6 m. In public use building like malls, cinema, shopping center larger width of stair can be used.
Design of Staircase Calculation – How to Calculate Rise and Tread Dimensions:
While planning any stair important dimension to find out first that is rise and tread of stair and their numbers.
Before finding out rise and thread fix following points,
Total Clear Distance Between two-floor (A) = 10’6” (3.20m)
Total Width of one flight or Distance between the first riser to last riser (B) = 1.80m
(For Better Understanding see fig. 1)
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First of all decide size of riser,
Riser Size = 7” (inch) (Range of riser = 6”to 8”)
Nos. of Riser = Clear Distance between two floors (A) / Size of Riser
= (10’6”/ 7”)
= 18 nos. (9 for first flight and 9 for second flight)
Now, we will calculate the size of tread,
(We know that for any stair numbers of tread for any single flight are one less than several rises.)
Number of threads on single flight = Nos. of Rising of single flight – 1
= 9 – 1
= 8 nos.
So, Size of Tread = Total width of Stair / Nos. of Thread
= 6’ (72”) / 8
Size of Tread = 9”
(This dimension can be changed as per types of the stair)
1) Size of Rise = 7”
2) Number of Riser on single flight = 9 nos.
3) Width of Tread = 9”
4) Number of Tread = 8 nos.