What is column size for 21 feet span for residential building, size of column depend on total load applied on the column, alignment of column and span between two column, There are axial loads and lateral loads. It also depends on various factors like number of floors, span between two column, is it short or slender.

The appropriate column size for a 21-foot span in a residential building depends on various factors, including the type of load the column will support, the material used for the column, and local building codes and regulations. Both wood and steel columns are common choices in residential construction, and the specific size will vary based on these factors. Here’s a general guideline: Wood Columns: For a 21-foot span, wood columns are typically constructed from engineered wood products like laminated veneer lumber (LVL) or glulam beams. Standard dimensional lumber is generally not suitable for such long spans. The size of the wood column will depend on the load-bearing requirements and local building codes. Common sizes for wood columns in spans like this might include 8×8, 10×10, or larger, depending on the specific design and load requirements. Consult with a structural engineer or architect to calculate the precise size and type of wood column needed for your residential building.

Steel Columns: Steel columns are a suitable option for longer spans or when higher load-bearing capacity is required.

The size and type of steel column will depend on factors such as the type of steel used, the load it needs to support, and local building code requirements. Consult a structural engineer to determine the appropriate size and type of steel column for your specific application.

You cannot fix the beam depth based solely on these parameters. How high is the column?, What is the load?, Are these steel beams and columns or are they reinforced concrete columns?, If so what grade of steel, or what grade of Concrete?, Without knowing all this no definite answer is possible.

When we go through the column design we should mention following point: 1) the possible distance or span and depth it all depend on load to which the beam is subjected, 2) column size depend on amount of load on the column acting on it by beam and RCC slab, 3) many axial and Lateral load acting on column, 4) large span greatly influence the bending moment not only on beam, but it also affect the column due to stress acting on it, 5) Thumb Rule for column design are appropriate for very small project like G+1,G+2 & G+3 Building and 6) column design for building construction it depend on many factors like topography, whether and size of building.

**What is column size for 21 feet span for residential building **

In this article, we will go through the essential thumb rules to be followed for giving a column layout. Ofcourse columns have to be designed in accordance to the total forces acting on the structure, but apart from that, it is essential for every Civil engineer and Architect to remember a few thumb rules so that they are prevented from making mistakes.

Minimum size of RCC column:-for residential building minimum size of an RCC column should not be less than 9”x 9” (225mm x 225mm) with 4 bars of 12mm Fe500 Steel with m20 grade of concrete and stirrups of T8@6″C/C.

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**Column size for 21 feet span g+1 **

For 21 feet span between two column, this general thumb rule, we will assume a structure of 1 storey/ground floor/1st floor/G+0 residential building, using standard 5″ walls, size of an RCC column should be 9”x 9” (230mm x 230mm) with 4 bars of 12mm Fe500 Steel with m20 grade of concrete and stirrups of T8@6″C/C.

**Column size for 21 feet span g+2**

For 21 feet span between two column, this general thumb rule, we will assume a structure of two floor/G+1/2 storey residential building, using standard 5″ walls, size of an RCC column should be 12”x 12” (300mm x 300mm) with 6 bars of 12mm Fe500 Steel with m20 grade of concrete and stirrups of T8@6″C/C.

**Column size for 21 feet span g+3**

For 21 feet span between two column, this general thumb rule, we will assume a structure of G+2/3 storey/three floor residential building, using standard 5″ walls, size of an RCC column should be 12”x 15” (300mm x 380mm) with 6 bars of 12mm Fe500 Steel with m20 grade of concrete and stirrups of T8@6″C/C.

**Column size for 21 feet span g+4**

For 21 feet span between two column, this general thumb rule, we will assume a structure of G+3/4 storey/four floor residential building, using standard 5″ walls, size of an RCC column should be 15”x 18” (380mm x 450mm) with 4 bars of 16mm and 2 bars of 12mm Fe500 Steel with m25 grade of concrete and stirrups of T10@6″C/C.

**Column size for 21 feet span g+5**

For 21 feet span between two column, this general thumb rule, we will assume a structure of G+4/5 storey /five floor residential building, using standard 5″ walls, size of an RCC column should be 15”x 21” (380mm x 530mm) with minimum 4 bars of 16mm and 2 bars of 12mm Fe500 Steel with m25 grade of concrete and stirrups of T10@6″C/C.

**What is column size for 30 feet span for residential building**

**What is column size for 25 feet span for residential building**

**What is column size for 20 feet span for residential building**

**What is column size for 15 feet span for residential building**

**What is column size for 10 feet span for residential building**

**CONCLUSIONS:- **

For 21 feet span between two column, this general thumb rule, we will assume a structure of G+2/3 storey/three floor residential building, using standard 5″ walls, size of an RCC column should be 12”x 15” (300mm x 380mm) with 6 bars of 12mm Fe500 Steel with m20 grade of concrete and stirrups of T8@6″C/C.