Number of standard sized steps required to build a stairway that reaches the top of a 5 storey building?

Question

If I had to construct a stairway that lead directly to the top of a 5 storey building, how many standard sized steps would the stairway comprise of?

Standard sized in the sense, the size of steps used inside a building which people can climb, unlike HUGE egyptian pyramid type steps.

Answer 1

Ergonomically and for safety reasons, stairs have to have certain measurements in order for people to comfortably use them. Building codes will typically specify certain measurements so that the stairs are not too steep or narrow. Building codes will specify:

- Maximum riser height, typically 8.25 inches (210 mm). Note that by specifying the maximum riser height and minimum tread length, a maximum slope is established. Residential building codes will typically allow for steeper stairs than public building codes.

- Minimum riser height: Some building codes also specify a minimum riser height, often 5 inches (125 mm).

- Minimum tread length, typically 9 inches (229 mm) including the nosing. However, most human feet are longer than 9 inches (229 mm), thus people's feet don't actually fit on the tread of the step.


The remaining piece of information is the height of each storey. (in the US spelled "story"). This dimension can range from 8' to 12' or more depending the type of strucuture and the intended use. A reasonable estimate might be 10 feet.

5 floors means four flights of stairs. If you wanted to get to the roof of a 5 story building, then you need five flights of stairs.

4 flights of stairs x 10 feet = 40 feet.
40 feet x 12 inches per ft = 480 inches

480 inches ÷ 8 inches per step = 60 steps.

When building a stairway, it is very important that every step be exactly the same height. When you take that first step, your brain instantly calibrates itself for the dimensions of the steps. If one step is off by even 1/4 inch, you will see many people stumble at that location.

The exact height of each riser (step) is dependent on the actual height of the stairway and the desired number of steps. Stairway height divided by riser height must equal an integer number. You can't build a fraction of a step.

480 inches ÷ 8.25 inches per step = 58.1818 steps. You can't build 0.1818 steps, so you'd have to install a 59th step that is only 1.5" tall. (Remember that 8.25" is the maximum allowed by the building code). Cheating and making step #58 an extra 1.5" tall will create a dangerous stumbling point.


In case you wanted to get to the roof of the five story building:
5 flights of stairs = 50 feet = 600 inches = 72 steps.


The second link below states the average riser height is 7.5".

600 inches ÷ 7.5 inches per step = 80 steps

Answer 2

It would depend on how high the building is, different occupancies may well have different story heights, for example high end offices may have higher ceilings and thicker floors than low income residential. I'd guess that between 75 and 100 steps would be a reasonable estimate.

[EDIT] She said the top of the building, so I took that literally. Also a 8 inch riser makes a very steep stairway. If one wants to use a 8" riser, they had better be going to an unoccupied roof or it won't meet the UBC (at least not the old version I have a copy of)(often used in the US, but not universal)

Section 3306 UBC 1985 ( I said it was old)
(c) rise and run, ... the rise of every step in a stairway shall not be not less than 4 inches nor greater than 7 inches...
EXCEPTIONS: 1. Private stairways serving an occupant load of less than 10 and stairways to unoccupied roofs may be constructed with an 8-inch maximum rise...

At a 12' story (storey) height the "top" of a five story building is 720", I consider a 7.2' riser reasonable (since I only build private residences) , but the story height could be less thus my answer of 75 to 100

Answer 3

5 storey building would require 4 stretches up (assiming the start is the ground floor). Four metres each level, 20 cm standard step gives you 4 x 4m / 0.2m = 80 steps!

Answer 4

cat has "9 lives" and it will take 2 seconds to figure out what it will do. " Obvious Man says: That cat will die if it jumps off a 10 storey building " my science teach always uses Obvious Man for stuff that is so easy to say