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Size of column depend upon several factors like load on the **structure, height of the building and distance between the two column**. In this post we will discuss standard size of Column for building construction.

**Size of the column **also depends upon the material used in column construction. Column based on material are classified as RCC column, timber column, short column, tied column and many more.

## Standard Size Of Column

As stated above **standard size of column** depends upon many factors. But for rough idea of column size refer the table below. Detailed information about standard size of column is discussed in the later part of this post.

Height of Structure | Different Levels | Size of Column in mm |

Upto 10 storey | 1 – 10 floors | 700 mm X 700 mm |

Upto 20 storey | 1 – 7 floors | 750 mm X 750 mm |

8 – 14 floors | 600 mm X 600 mm | |

15 – 20 floors | 450 mm X 450 mm | |

Upto 30 storey | 1 – 10 floors | 800 mm X 800 mm |

11 – 20 floors | 650 mm X 650 mm | |

21 – 30 floors | 470 mm X 470 mm |

### Standard minimum size of column and details

Details of minimum size of column that is necessary for any structure based on its height along with other details for column are given below.

**Column details for 1 storey (ground floor) building**

Minimum size of column | 9″ X 9″ (225mm X225mm) |

Main Bars (Main Steel bar dia) | 4 bars of 12mm dia |

Stirrups for shear reinforcement | 8mm dia bars @ 6″ spacing |

Preferred grade of concrete | M20 Concrete (1 : 1.5 : 3) |

**Column details for 2 storey (G+1) building**

Minimum size of column | 9″ X 12″ (225mm X300mm) |

Main Bars (Main Steel bar dia) | 6 bars of 12mm dia |

Stirrups for shear reinforcement | 8mm dia bars @ 6″ spacing |

Preferred grade of concrete | M20 Concrete (1 : 1.5 : 3) |

**Read: Standard Room Sizes and Dimension**

**Column details for 3 storey (G+2) building**

Minimum size of column | 12″ X 12″ (300mm X300mm) |

Main Bars (Main Steel bar dia) | 6 bars of 12mm dia |

Stirrups for shear reinforcement | 8mm dia bar @ 6″ spacing |

Preferred grade of concrete | M20 Concrete (1 : 1.5 : 3) |

**Column details for 4 storey (G+3) building**

Minimum size of column | 12″ X 14″ (300mm X350mm) |

Main Bars (Main Steel bar dia) | 4 bars of 16mm dia + 2 bars of 12mm dia |

Stirrups for shear reinforcement | 10mm dia bar @ 6″ spacing |

Preferred grade of concrete | M25 Concrete (1 : 1 : 2) |

### Standard Thumb Rule Used In Construction

Nowadays minimum size of column used in construction irrespective of small building is 9″ X 12″ (225mm X300mm). Recommended grade of concrete for building construction is M20 grade, that is in the ratio of 1 : 1.5 : 3 (1 part of cement and 1.5 part of sand and 3 parts of coarse aggregate with 0.5 parts of water).

**Below is the summary of the standard size of column used in 2021.**

- Column Size – 9″ X 12″ (225mm X300mm)
- Main reinforcement – 6 bars of 12mm dia Fe 500 Steel
- Stirrup rings – T8mm dia bars @ 6″ (150mm) spacing
- Concrete – M20 Grade of concrete (1 : 1.5 : 3)

### Quick Formula For Dimension of Column

A quick method top find the size of column based on the strength of the material and maximum load to be applied on column is given below.

N_{max }= A * f * Reduction Factor

Where,

- N
_{max}= Maximum load that can be applied on column - A = Area of Column in m
^{2} - f = Strength of material in KN/m
^{2} - Reduction Factor = Coefficient for taking into account risk and material variation

## Factors Affecting Column Size

There are many factors that affects the size of column but most important ones are height of the building or structure, distance between columns, alignment of column and many other factors.

**Factors affecting column size are given below:**

- Height of the building or structure
- Distance between adjacent columns
- Load of the structure
- Architectural consideration

Let us look in detail how column size is affected by each factors and what size should be preferred for such situations.

### Height of the structure

As height of the building increases the dead load and live load on the building also increases. To compensate for the increase in load we need to increase the strength of the RCC structure.

As we know that column transfer load from beams and slab to the foundation of the structure of the building. Thus size of column and reinforcement in column is needed to be increased.

### Space Between Adjacent column

Distance between the each column in a building should be preferably kept same between centres of 2 column. If column are placed closer to each other then the size of column can be reduced and vice versa. Thus space between column is directly proportional to the size of the column.

Distance between column is directly proportional to column size

For a 9″ X 9″ Column, the maximum distance between the column should not be more then 4 meters. If due to architectural or any other condition distance is needed to be more then size of the column is needed to be increased.

### Load on the structure

No standard size can be fixed for similar height building as each structure has different function. As we know to counter the increase in height and dead load of structure, size of column is increased. Similarly for balancing live load, wind load and other loads the size of column is needed to be selected accordingly.

Thus before deciding the size of the column proper load that is going to come on the building should be worked out.

## Why No Standard Size Of Column

As you have seen above that the size of column depends upon many factors, thus it would be hard to fixed the size based on these factors.

Size of column depend upon the load to be supported, type of column, distance between column, architectural design, and many other factors affect the size of column. By varying the percentage of steel the size of column can be reduced or increased.

Based on these factors we have to assume the size of column and check for safety of the structure.