What is stair?
A continuous whole set of steps to join the two floors of structure is called stair. There’s two basic stair parts, tread and riser. The room or area where stair is constructed is called stair case. The rectangular shape unit is called step.
The continuity of steps is called flight. A flight length usually consist of 3 to 15 steps. If there’s more than 15 steps, there’s more flight provided. There’s a space provided b/w two flights to stay, which is usually bigger than step is called landing.
The horizontal surface of step is called going, while the its distance is called tread. The size/length of tread should be between 25cm to 30cm (10 to 12 inches).
The vertical surface of step is called riser. The size/height of riser should be b/w 15cm to 22.5cm (6 to 9 inches). If the step is rectangular (which is common) it is called flier step.
Sometimes the triangular shape steps are provided on landing, which is called winder. How much should be width of stairs? The width of stair shouldn’t be less tha 3feet (36 inches) or 92cm.
Stairs according to material:
According to material stairs are made up with wood/timber, steel, brick masonry, stone masonry and concrete etc. According to shapes, That are designed as straight flight, quarter turn, half turn, geometrical, bifurcating and circular stairs.
Winder (triangular steps) are provided at turning point instead of landing. Nowadays escalators are being use in buildings to provide ease, which is shaped as steps and move up and down.
Stair parts list:
Following are the stair parts names, components and stair parts terminology.
- Pitch or Slope
- Newel Post
- Head Room
Part of set consist of more then two steps is called flight. For low height single flight is provided while for more height two or more flights are provided.
To support the flight and steps, there’s a inclined slab is provided below the flight is called waist.
A flat floor between two floor is provided to stay, which is called landing. Its purpose is to stay if you get tired.
steps of common stair which are rectangular in shape are called fliers.
When there is less stair case area, there’s triangular shape steps are provided instead of landing, these triangular shape steps are called winders.
Horizontal or upper surface of step is called going.
Width of horizontal surface of step is called tread.
Veritical surface of step is called riser.
Height of vertical surface (riser) is called rise.
Pitch or slope:
The angle formed between the floor level and stair is called Pitch or slope. pitch or slope of stair should be between 25 to 40 degree.
To keep the stair safe while going up and down, there’s a steel or wooden strip is provided which is called hand rail. It is provided parallel but opposite to wall.
To support the handrail, and join it with stairs step a vertical support is provided which is called stair baluster. Baluster can be of steel and wooden.
At the start or end of stairs, there’s a more thicker & stronger vertical support is provided which is called newel post. Handrail, baluster & newel post are parts of Stair railing.
The height from step of stair to the slab is called head room. Head room shouldn’t be less than 2.5 meter (8 feet).
A little grown up edge of tread is called nosing.
Characteristics of good stair:
Stairs is one of important part of building. A good stair should have following characteristics.
- Stairs should be in the center of building, so everyone can access it easily.
- All the steps of stairs should be constant & well constructed.
- Slope of stairs should be between 25 to 40 degree angle.
- Width of stairs should must not be less then 3 feet (85 cm), so the two people can move up & down easily at same time.
- Height of head room shouldn’t be less then 2.5 meter (8 feet).
- Height of hand rail from steps shouldn’t be less than 85 cm (3 feet).
- There shouldn’t be more than 15 steps, nor less than 3 steps in a single flight.
- Material used in stairs construction should be of good quality. e.g. R.C.C, steel etc.
- There should be proper ventilation for stairs.
Designing of stair:
Keep it in mind to provide ease for the users, while designing of stairs. Further the design make it more attractive. following are the principles of designing of stairs.
Tread and riser calculation formula:
Formula to calculate nos of riser = height of stair case/height of riser
- Let suppose height of floor is 10′ (3 m) = 120″ (304.8 cm)
- take a riser height 7″ (17.78 cm). (which is most commonly used).
- Nos of riser= 120″/7″ = 17 (in inches)
- Nos of riser= 304.8/17.78 = 17 (in cm)
- For tread simply deduct 1 from riser.
- Nos of tread = 17-1 = 16
Problem/error in stair design:
These 17 steps are provided in a single flight, but above we red that there shouldn’t be more than 15 steps in a flight. So what we do to counter this problem.
Simply increase a little in riser height can solve this issue. Like: take riser height= 8″, so the total steps will be 15, if you take riser height= 9″, total steps will be 13.
This simple thumb rule can be implemented, but if you dont want to inrease thr riser height, you can provide 2 flights. But if you have less space/stair room area then go with increment in riser height .
Types of stair according to material:
Following are the materials that can be used in stairs construction.
The wooden stairs made up with all timber. Before the use of concrete, wood were preffered for stairs casting. But there were demerit, it wasn’t fire resistant.
But nowadays wood is expensive, the places where wood is cheap there’s already wood is being used. This type of stairs are joined with the help of steel nails and wooden pins.
Metal and steel is being used in stairs casting which is called metal stair. These are made up with stringer and metal channels. In this type there aren’t riser provided but just treads.
Sometimes it fully metal stairs, but nowadays there’s a marble slab provided at tread. These stairs are usually used at places where wear and tear produced e.g. godowns, factories. They are strong+durable & fire resistant.
Stairs that are made up of concrete. These stairs are cheap, easy to construct, Stronger and durable. These are very popular in modern construction. Concrete stairs has two types.
Precast concrete stair:
It is manufactured with plain concrete sills or precast concrete in a controlled enviroment, which is then install on site.Sometime steel bars used in precast manufacturing while it doesn’t used in plain concrete.
R.C.C concrete stair:
R.C.C stairs are made up with reinforced concrete. On the exterior surface of stairs, tile and marble are placed. This make it more attractive, but make sure that tread shouldn’t be much slippery.
R.C.C & precast stairs are most commonly used nowadays.
Following are the advantages of R.C.C stairs:
- R.C.C stairs can be made up in any shape.
- R.C.C stairs are durable.
- Its fire resistant.
- It don’t produce more sound while walking upon.
- It looks more attractive, if constructed well.
- R.C.C stair is easy to clean, further low maintenance cost.