STAIR DESIGN FOR RESIDENTIAL BUILDING

INTRODUCTION

One of the important components of the building especially for those with more than one floor levels or building constructed at height is stairs.

Stairs are building components which allow building users or households to move from one floor level to the other, so it is connector or communication path between floors or levels.

Stairs are composed with series of steps at certain inclination angle to allow vertical movements inside and outside the building.

Types of Stairs 

Stairs can be classified into number of types as depending on its architectural design inside the building, the followings are some types of stairs that can be found in different buildings.

Main parts of stairs.

The following are standard requirements for each stair component, so as to have comfort and serviceable stair.

Landing, this is horizontal slab between two or more  flights, which  is used as resting or changing in direction point.

Riser, t is the vertical portion of step, where for comfortability it should not exceed 190mm.

Going, this is the horizontal portion of step, where by for comfortability it should not be less than 225mm.

Flight, is the series of steps between landings, where by maximum and minimum number of steps for one  flight is 11 and 3 respectively.

Handrail, is the part of staircase that people hold onto for support when going up or down.

Newel, this is the handrail support, which hold handrails in their position and make them able to support staircase users. 

Balusters, these are vertical members that provide support to handrails between newels.

How to design a stair?

Example

If you are required to design a stair that meet the standard requirements for residential building with height allowance of 3200mm between floors.

Step 1. Choose your riser height

The choice of rise height is dependent of the use of the building, for residential building we have, let’s take riser height= 160mm

Step 2. Calculate number of risers and treads

            Number of risers    =   

                                 = 3200/160

                                             =  20

            Number of treads    =  Number of Risers – 1

                                             = 20 -1

                                             =  19   

Step 3. Determine your tread

            From Riser + Tread should neither be less than 400mm nor greater than 550mmm

            Lets choose 250mm as our tread, then 160 + 250 = 410 OK

Step 4. Check your stair inclination angle

         Stair inclination angle tan α = 

                                          α   = tan ^-1( ^Rise/Tread )

                                         α  =  tan ^-1 (Rise/Tread )

                                          α  = 32.6⁰ checked OK since it is less than 38⁰

Step 5. Possibility of landing usage.

In our stair we have 20 steps, since for a one flight maximum number  of steps is 11, then we will needed to provide landing to separate flights, so we will have two flights.

Number of steps in each flight = 20/ 2

                                                                          = 10

Finally we will have a stair of 20 steps inclined at 32.6⁰, composed by two flights separated by one landing; each flight will have 10 steps.