# Dog legged Staircase and its design

Dog legged Stair Case:

Stairs provide access for the various floors of the building. The stair consists of series of steps(flight) with landings at appropriate intervals. Stairways are made up of individual steps. Each step consists of a tread and a riser. The tread is the flat part that you step on. The riser is the vertical(up and down) part between each tread in the stairway.
Dog legged stair case is the most economical staircase.  These stairs are arranged with two adjacent flights running parallel with a mid landing. Where space is less, dog legged staircase is generally provided resulting in economical utilization of available space.  In this type of staircase landing is provided corresponding to the level at which the direction of the flight changes.

## 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 lass than width of the stair flight at 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.

## Dog legged Staircase Design:

Designing a Dog legged staircase for a residential building where space provided is 2.5m x 4.5m and floor to floor height is 3.3m
Solution:
Generally for residential buildings we adopt Rise and tread of each step is 150mm and 225mm.
Dimensions of Stair hall
l = 2.5m x 4.5m
Height of Floor = 3.3m Total No. of flights = 2 . So, height of one flight = 3.3/2 = 1.65m
Rise = 150mm, Tread = 225mm
No. of risers = 1650/150 =11
Hence, Number of treads = 11-1 = 10
Adopting width of stair = 1.2m
For 10 treads , the length required = 10 x0.0225 = 2.25m
Width of landing = (4.5-2.25)/2 = 1.125m