Dear Sir,For 17.6 ft span between two columns, what should be size of the column

Size of the columns

The size of the columns depends on the total load on the columns. Minimum size of the column should not be less than 9”x9”. 9”x9” columns are to be used for a single storey structure with M15 grade of concrete. In case, 9”x9” column size is to be used for 1 and half storey structure, then it is advised to use M20 grade concrete. A safe and structurally sound column size for a 1 and half storey structure should not be less than 12”x9” using M15 grade concrete. This should be in your most preferred and practical options list.

Distance between the columns

Try to maintain equal distance between the centres of two columns. Always plan a column layout on a grid. The distance between two columns of size 9”x9” should not be more than 4m centre to centre of column. If larger barrier free distances are required then going for larger column size is to be used.