Let’s take an example:
The height of one floor = 12 feet.
Height to be acquired by one flight = 12/2 = 6 feet.
Risers = 6″ = 0.5 feet.
Number of risers = Height of flight / Riser = 6/0.5 = 12
Tread = 10″ = 0.8 feet.
Number of treads = (Numbers of risers -1) = 12 – 1
Thickness of waist slab = 6″ = 0.5 feet
Length of step = 5 feet
Volume Of Concrete For Steps:
Volume of one step = 1/2 x riser x tread x length of step
= 1/2 x 0.5 x 0.8 x 5 = 1.03 = 1 cubic feet.
As we have 11 steps in a flight the volume of steps for the first flight = 11 x 1 = 11 cubic feet.
Concrete Volume For Waist Slab:
To calculate the volume of concrete for the waist slab we need to know the inclined length of the waist slab.
The horizontal length of waist slab = Tread x Number of steps
=0.8333′ x 11 = 9.2 feet.
The height of the top of the landing from floor = Number of riser x Height of riser
= 12 x 0.5 = 6 feet.
The volume of concrete for waist slab = Inclined length of waist slab x Width of waist slab x Thickness of waist slab
= 11′ x 5′ x 0.5′
= 27.5 cubic feet
∴ The volume of concrete for first flight = Volume of waist slab + Volume of steps
= 27.5+11 = 38.5 cubic feet
Volume Of Concrete For Landing Of Staircase:
Length of landing = 10.5 feet
Width of landing = 5 feet
The thickness of landing = 0.5 feet
∴ Concrete volume for landing = 10.5′ x 5′ x 0.5′ = 26 cubic feet.
Concrete Volume for 2nd Flight Of The Staircase:
As the 1st light and 2nd flight are the same in our staircase so the volume of concrete will be the same.
Concrete volume for 2nd flight of the staircase = 38.5 cubic feet.
∴ Total volume of concrete for staircase = Volume of first flight + Volume of second flight + Volume of landing
= 38.5 + 38.5 + 26
= 103 cubic feet.
Well, this is the wet volume of concrete. To convert wet volume into dry volume we need to multiply with 1.54
∴ Dry volume of concrete = 103 x 1.54 = 159 cubic feet.
Quantity Of Materials For Staircase:
We will calculate for 1:2:4 Concrete mix.
1. Volume of cement = 1/7 x Dry volume = 1/7 x 159 = 22.66 cubic feet.
∴ Number of Cement bags = volume of cement / Volume of cement bag = 22.66 / 1.25 = 18 No’s of bag. (The volume of one bag of cement of 50 kg = 1.25 cubic feet)
2. Volume of Sand = 2/7 x Dry volume = 2/7 x 159 = 45 cubic feet.
3. Volume of Aggregate = 4/7 x Dry volume = 4/7 x 159 = 91 cubic feet.
Note: Here, I have used cubic feet unit and 1:2:4 mix ratio, you can use cubic meter unit and any other mix ratio of concrete.