Determining the exact column footing size for a building requires a detailed structural analysis, taking into account factors like the building’s design, materials, and local soil conditions. Generally, as the number of storeys increases, the loads on the columns and footings also increase.
Size of footing depends on various factor bearing capacity of soil, number of columns, total dead and live load and other loading and structural aspects of construction. Without knowing bearing capacity of soil and load coming over it, we can only predicting the size of footing.
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Depth of foundation depends on soil condition, type of soil, hard starta beneath the ground level and safe bearing capacity of soil, type of construction like wall, live load and dead load. When all coming load on footing will be 300KN/floor and safe bearing capacity (SBC) is 250KN/m2, generally footing size 1.5m×1.5m to 2m×2m is applicable.
Depth of footing ranging between 3 feet to 9 feet deep beneath the ground level, depending on soil types and load calculation. Footing size for residential building depth should be not less than 3 feet on strong bearing capacity of soil like gravel and sand.
Width and depth of foundation calculated on the basis of safe bearing capacity of soil, type of soil and all the live and dead load coming on it,without knowing bearing capacity of soil and load coming over it, we can only predicting the size of footing. Actual size is calculated by structural engineer by measuring the safe bearing capacity of soil and all the load coming on it. In this article we use various Thumb Rule for column footing size for 1 to 5 storey building.
Footings are an important part of foundation construction. They are typically made of concrete with rebar reinforcement that has been poured into an excavated trench. The purpose of footings is to support the foundation and prevent settling and it safely transfer the all coming load to bed of soil.
In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the footing. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil.
For the stability of your building concrete structure, you would like to have soil that has good bearing capacity. Gravel and sand are the soils with higher bearing capacity while silts and clays typically have lower capacities.
Column footing size for 1, 2, 3, 4 and 5 storey building
Size of footing depends on various factor bearing capacity of soil, number of columns, total dead and live load and other loading and structural aspects of construction. Without knowing bearing capacity of soil and load coming over it, we can only predicting the size of footing by thumb rule.
Column footing size for 1 storey (G+0) building
In general, the standard column footing size for a G+0/1-storey residential building is (L × H × W): 3.5 × 3.5 × 3.5 feet (1 × 1 × 1 meter). So the standard size of the column footing for a one storey building is 3.5 feet long, 3.5 feet high, and 3.5 feet thick.
For 1 storey (G+0) house or in simple ground floor building, general thumb rule, using standard 9″ thick walls, we recommended size of column footing should be 3.5’×3.5’×3.5′ (1m x 1m×1m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity in which width dimensions is 3.5’×3.5′ and depth of footing should be minimum 3.5′ provided with Mesh bar of T10@6″C/C of Fe500 Steel with m20 grade of concrete and minimum column size 9″×9″.
Column footing size for 2 storey (G+1) building
In general, the standard column footing size for a G+1/2-storey residential building is (L × H × W): 4 × 4 × 4 feet (1.2 × 1.2 × 1.2 meters). So the standard size of the column footing for a two storey building is 4 feet long, 4 feet high, and 4 feet thick.
For 2 storey (G+1) house or in simple 2 floor building, general thumb rule, using standard 9″ thick walls, we recommended size of column footing should be 4’×4’×4′ (1.2m x 1.2m×1.2m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity in which width dimensions is 4’×4′ and depth of footing should be minimum 4′ provided with Mesh bar of T10@6″C/C of Fe500 Steel with m20 grade of concrete and minimum column size 9″×12″.
Column footing size for 3 storey (G+2) building
In general, the standard column footing size for a G+2/3-storey residential building is (L × H × W): 5 × 5 × 5 feet (1.5 × 1.5 × 1.5 meters). So the standard size of the column footing for a three storey building is 5 feet long, 5 feet high, and 5 feet thick.
For 3 storey (G+2) house or in simple 3 floor building, general thumb rule, using standard 9″ thick walls, we recommended size of column footing should be 5’×5’×5′ (1.5m x 1.5m×1.5m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity in which width dimensions is 5’×5′ and depth of footing should be minimum 5′ provided with Mesh bar of T12@6″C/C of Fe500 Steel with m20 grade of concrete and minimum column size 12″×12″.
Column footing size for 4 storey (G+3) building
In general, the standard column footing size for a G+3/4-storey residential building is (L × H × W): 6 × 6 × 6 feet (1.8 × 1.8 × 1.8 meters). So the standard size of the column footing for a four storey building is 6 feet long, 6 feet high, and 6 feet thick.
For 4 storey (G+3) house or in simple 4 floor building, general thumb rule, using standard 9″ thick walls, we recommended size of column footing should be 6’×6’×6′ (1.8m x 1.8m×1.8m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity in which width dimensions is 6’×6′ and depth of footing should be minimum 6′ provided with Mesh bar of T16@6″C/C of Fe500 Steel with m20 grade of concrete and minimum column size 12″×16″.
Column footing size for 5 storey (G+4) building
In general, the standard column footing size for a G+4/5-storey residential building is (L × H × W): 7 × 7 × 7 feet (2.1 × 2.1 × 2.1 meters). So the standard size of the column footing for a five storey building is 7 feet long, 7 feet high, and 7 feet thick.
For 5 storey (G+4) house or in simple 5 floor building, general thumb rule, using standard 9″ thick walls, we recommended size of column footing should be 7’×7’×7′ (2.1m x 2.1m × 2.2m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity in which width dimensions is 7’×7′ and depth of footing should be minimum 7′ provided with Mesh bar of T16@6″C/C of Fe500 Steel with m20 grade of concrete and minimum column size 12″×18″.
Conclusions:-
In general, the standard column footing size for a G+2/3-storey residential building is (L × H × W): 5 × 5 × 5 feet (1.5 × 1.5 × 1.5 meters).