TUTORIALS

How to Design & Compute the Volume of Concrete for U shaped stairs

There’re two analogous flights in U shaped stairs. 180 degree is required.
Riser dimension maximum = 7”
Riser dimension minimum = 4”
Tread dimension minimum = 10’’
Tread dimension maximum = 12’’
Step length must be at least 3’

Breadth is equal to 5’ [First floor]
Floor to floor height is required, from ground floor to first floor.
One step height, riser height is equal to 0.5 feet
Landing is equal to 10’ 6” [Gap should be at least 6”]

Waist slab should be at least 6”
Floor height is equal to 10 feet
1 flight height is equal to 10/2 = 5 feet
Number of risers is equal to flight height/riser = 5/0.5 = 10 numbers
Tread length is equal to 10” is equal to 0.8 feet
Number of treads is equal to [Number of risers – 1] = 10 – 1 = 9 numbers
Waist slab thickness is equal to 6” is equal to 0.5 feet
Step length is equal to 5 feet

CONCRETE VOLUME FOR STEPS:

One step volume is equal to ½ x tread x riser x step length =
One step volume = ½ x 0.8 x 0.5 x 5 = 1.03 ft³
There’re 9 steps in a flight, then volume of steps for the initial flight = 9 x 1.03 = 9.27 ft³

CONCRETE VOLUME FOR WAIST SLAB:

Determine the inclined length of the waist slab
Waist slab inclined length = square root (horizontal length)² + (height)²
Waist slab horizontal length is equal to tread x Number of steps = 0.8333’ x 9 = 7.4 feet
Determine the height of the top of the landing from floor
= risers numbers x riser height = 10 x 0.5 = 5 feet

Waist slab inclined length = square root (horizontal length)² + (height)²
Waist slab inclined length = square root (7.4)² + (5)²
Waist slab inclined length = square root (79.76) = 8.93 feet

Waist slab volume = Waist Slab inclined length x Waist Slab width x Waist Slab thickness
Waist slab volume = 8.93’ x 5’ x 0.5 = 22.32 ft³
Initial flight volume = Waist Slab volume + Steps volume = 22.32 + 9.27 = 31.59 ft³

LANDING VOLUME

Landing length = 10.5 feet
Landing width = 5 feet
Landing thickness = 0.5 feet
Landing volume is equal to 10.5 x 5 x 0.5 = 26 ft³

2nd FLIGHT VOLUME

1st and 2nd flight are same, therefore the volume will be same , i.e., 31.59 ft³
Stair Overall volume = 31.59 + 31.59 + 26 = 89.19 ft³

MATERIALS AMOUNT FOR STAIRCASE

Wet volume = 90.4 ft³
Dry volume = 90.4 x 1.54 = 139.21 ft³
Computation for 1:2:4 concrete mix:
Cement volume = 1/7 x dry volume = 1/7 x 139.21 = 19.88 ft³
Number of bags = 19.88/1.25 = 15.90, approx 16 bags
Sand volume = 2/7 x dry volume = 2/7 x 139.21 = 39.77 ft³
Aggregate volume = 4/7 x dry volume = 4/7 x 139.21 = 79.54 ft³

Lecturer: Civil Study