How to create the design of a single flat stair

In this exclusive construction video tutorial, the renowned engineer S.L. Khan provides some useful tips for civil engineering students. In this video, he teaches you how to make the design of a single flat stair.

The dimension of the stair is given as follow :-

18 x 3.5 x 10, here run is 18 feet and height is 10 feet.

Now, the process will be shown to determine the tread, rise, pitch and number of steps for the stair.

The process is divided in step 1 and step 2.

Step 1 : In this step, the following points are included :-

1) Assume proper rise for one step.

2) Determine no. of rise.
No. of rise = Total height/height of step

3) Calculate no. of treads
No. of treads = No. of Rise - 1 (as there is no tread in the upper top of the stair i.e. may be a landing or slab)

4) Work out the size of tread.

5) Check for pitch

The slope of the stair is taken as 25 degree or 35 degree.
Assume rise as 6 inches. (i.e. height of one step)
No. of rise = total height/height of step = 10/0.5 (as 6 inches = 0.5 feet) = 20 Nos

N.B. In concrete, the sizes of aggregates come in very large size and lots of air is included in it.

Therefore, number of rise = 20 Nos.
Number of treads = Number of rise - 1 = 20-1 = 19
Therefore, number of treads = 19
Size of one tread = Run/no. of treads = 18 feet/19 x 12 (convert to inches) = 11.37 inches.
Therefore, tread's size = 11.37 inches.

The slope of the stair will be determined as follow :-
The slope is taken as α = tan-¹ (Rise/Run) = tan-¹ (6/11.37) [as tread = 11.37] = 27.82 Deg.

To learn the process for step 2, go through the following video tutorial.

Video Source: SL Khan