What Is the Staircase?
A staircase is a series of steps that allow ascent and descent from one level to another in any building or structure. There are many types of staircases on the basis of design. A straight staircase is the simplest one. Other types include spiral, circular, open newel, and many others. One of the common types is the Dog-Legged Staircase, which is discussed in detail here.
What Is Dog-Legged Staircase?
The dog-legged staircase consists of two flights running opposite to each other with a landing at the point where the direction of flight is changed. It is the simplest form of the staircase after the straight staircase and it is widely adopted too. Construction of the dog-legged staircase is economical because of its compact design. The staircase utilizes the space provided. It just requires space that is twice the width of steps.
The fact behind its Name
A dog-legged staircase looks like a dog in elevation. The slope of the staircase is similar to the angle between the legs of a dog. That is why it is named the dog-legged staircase.
Is the Length of Flight Equal?
No, the length of both the flights is not needed to be equal. In most of the cases, it is kept unequal. This staircase is provided in residential, commercial, institutional, and public buildings.
Suitability of Dog-Legged Staircase
When much space is not available, the dog-legged staircase is most suitable. The space required for the dog-legged staircase is equal to twice the width of the treads.
Components of the Dog-Legged Staircase
1- Tread: The portion of the staircase on which the foot is stepped on is called tread.
2- Riser: The part of the staircase between two treads is called a riser.
3- Newel post: The vertical post at the start and end of the flight is called a newel post.
4- Baluster: The vertical support installed throughout the length of a flight on which a handrail is supported to prevent the fall is called a baluster.
5- Handrail: An inclined rail provided at an optimum height so that it can support the person while ascent or descent is called a handrail.
6- Landing: A platform provided to break the continuity of flight for providing rest to the user is called landing.
7- Pitch: The angle the line of nosing makes with horizontal is called pitch.
8- Line of nosing: An imaginary line parallel to the slope of the staircase that joins the nosing of the staircase is called the line of going.
Advantages of Dog-Legged Staircase
1- Efficient use of space: This type of staircase covers much less area than straight They allow for a more compact stair arrangement.
2- Privacy: These stairs are great if you want to separate one floor from another for any reason. As the top floor cannot be seen and vice versa, these stairs offer ample privacy to users.
Disadvantages of Dog-Legged Staircase
1- Difficult to build: These stairs are not very easy to build.
2- Handrails on these stairs also need careful planning.
Requirements of a good staircase
Any well-planned stair should meet the following criteria for easy, quick and safe ascent/descent.
1- Location: It should be located so as to get sufficient light and ventilation with easy access from all the rooms.
2- Length of flight: A flight should have not lesser than three risers and not more than 16 risers.
3- Pitch of stair: Stairs are pitched (Angle of staircase) from 15 degrees to 55 degrees; however recommended angle is between 25 to 40 degrees. Pitch of long should be flattened by using landings.
4- Landing: Width of the landing should not be less than the width of the stair flight in any case.
5- Step Proportions: The rise/going of each step in one flight and in flights and landing between floors should be equal. Any variations may spoil rhythm. The rise/going are proportioned so as to ensure comfortable access.
Example 1: Dog-Legged Staircase Design
Design a dog-legged staircase for a residential building. The space available for the stairwell is 2.5 * 4 m. The floor to floor height is provided at 3.1 m.
- For residential a building, normally the riser height is taken from 150-190 mm.
- So, let us provide the riser of a height of 160 mm.
- Also, tread depth is taken as 225 mm.
- Stairwell dimensions = 2500 * 4000 mm
- Floor height = 3100 mm
- Total number of flight to be provided = 2
Therefore, height of 1 flight = 3100/2 = 1550 mm
- Rise = 160 mm
Therefore, Number of risers in a flight = 1550/160 = 9.6 Say 10 risers
- Number of treads = Number of riser – 1 = 10 – 1 = 9
- Let Tread width = 1.2 m
- Length for 9 treads = 9 * 0.0225 = 0.2025 mm = 2.025 m.
- Width of landing = (4 – 2.025)/2 = 0.9875 m which is approximately 1.0 m
Example 2: Dog-Legged Staircase Design