How to calculate the number of risers & treads in a staircase?/ Design of risers & treads in a staircase.

 Let us calculate the number of risers & treads for the below-given drawing.

Given data:

Landing slab thickness = 200mm.

Top to bottom surface landing height = 1.3m. = 1300mm.

The inner span between the landings = 2m. = 2000mm.

First, let us assume the riser depth as =160mm.

So, the number of risers

                                       = landing height ÷ riser height.

   Top-to-top landing height 

                                       = Top to bottom height of landing + landing thickness

                                      = 1300mm + 200mm.

                                      = 1500mm.

The no. of risers 

                 = [1500mm ÷ 160mm]

                 = 9.375 nos.

   As the risers should be the whole number, let us provide 9 nos. of risers & we will divide the landing height by the number of rises to get the corrected riser depth.

The actual height of the riser

                                         = landing height ÷ no. of risers

                                        = 1500mm ÷ 9nos.

                                        = 166.66mm.                   

Now, the number of treads

                 = [number of risers - 1]

From the above drawing, you can observe that the total no. of treads is always less by one from the given no. of risers.

So, the number of treads 

            = [9 nos. - 1]

            = 8 nos.

The tread width 

          = [horizontal clear span between landings ÷ the no. of treads.]

          = 2000mm ÷ 8nos.

          = 250mm.

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