Types of Footing: Wall, Combined, Isolated & various Footings

Types of Footing

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Different types of footing are most commonly used in building construction.

They can be both deep as well as shallow depending upon their depth.

Basically it is the enlargement of the base of a column or wall for the purpose of distributing the load on the supporting soil under pressure that suits its properties.

Different types of footing used in buildings:

Wall Footing:

Wall footing is of two types i.e., simple and step wall footing.

For light structures or temporary structures, simple footings are provided, they have a solid base under the walls with no steps on the wall.

In the case of load-bearing structures, the wall area is stretched step by step until the level of the foundation is reached, with a layer of concrete 15 cm to 20 cm thick also provided under the wall.

Simple Wall Footing:

Wall Footing

When a certain load, carried by a column, is supported on a subsoil whose bearing strength is estimated at some definite figure.

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Stepped Wall Footing or Spanning Wall Footing:

Stepped Wall Footing

The area of the wall is increased so as to transmit the load over a large area of soil.

The footing depth is generally limited to 1 meter, but in the case of black cotton soil, the foot should be moved below the area without cracks.

 The simple footing is used under compound walls and light structures while stepping footing is used under load-bearing structures.

Column Footing or Separate Footings or Pad Footings:

Pad

These types of footing are used to support individual columns; they can either of phased type or approximate on a solid basis.

Generally, 15 cm offset is provided on all sides of the concrete bed, it is the most common footing.

These are used to support individual columns.

In frame structures, it is customary to have separate legs for each column.

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They can be square, rectangular, circular, or sloping, depending on the distribution of load required.

Isolated Sloped Column Footing is used in RCC Buildings.

Combined Footing:

Combined Footings

Sometimes two columns are located very close to each other in a structure.

If separate footings are provided under these columns, they may interfere with each other.

Therefore, it is necessary to provide a combined footing, they are made of reinforced concrete.

The essential condition in this type of footing is the centre of gravity of the column load and the centroid of the footing should match.

Types of Combined footings:

Rectangular footings are provided under two columns where the column is equal at arc load

Trapezoidal footings are provided when the two columns are unevenly loaded.

Inverted Arch Footing:

Inverted Arch Footing

This types of footing are old foundation, suitable for building bridges, tanks, underground sewers and reservoirs.

This type of foundation can be used for structures where loads are concentrated on columns or where a load is distributed over a large area or where the bearing capacity of the soil is poor.

An inverted sectional arch is constructed below the columns; the rise of the arch is from 1 / 10th to 115th of the period.

Cantilever Footing or Strap Footing:

Cantilever Footing

This types of footing are also called strap footing, which is used when a column is near the plot boundary and column footing is not allowed to extend beyond the plot boundary.

In this footing, the load of the column near the boundary is supported on the strap beam.

The strap beam originates from a column which is in the interior of the plot.

Grillage Foundation:

Grillage Foundation

Grillage foundations are used to convey heavy loads from steel columns to low bearing capacity soils.

Such foundations are lighter and economical as they avoid deep digging.

Footing consists of steel beams in one or two levels.

Beams in each tier are held in place by spacer bars with a diameter of 20 to 25 mm.

The space between the beams is filled with concrete to protect the steel beam front corrosion.

Raft or Mat Foundation:

Mat Foundation

The types of footing consist of thick reinforced concrete slabs that cover the entire area below the structure on sub-soil.

The slabs are reinforced with right-sided straps at each other and the stiffness of the slab bridges over loose patches in the soil.

It is suitable where the ground is soft; soils or marshes with low bearing capacity, and where sub-water conditions are uncertain.

In the built-up ground, softer soils or marshy sites have a lower value of its bearing strength, heavier concentrated structure loads are usually supported by providing a raft foundation.

Also, read 1.Deep Foundation 2. Deep Foundation 3. Types of Aggregates

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Types of Footing FAQ:

What are footings in construction?

Footing aims to support the foundation and prevent settling.
The footing is particularly important in areas with troublesome soils.

What are the 3 types of foundations?

1.Strip footing.
2.Raft or Mat footing.
3.Isolated or pad footing.

What is the cheapest type of foundation?

slab foundations.

What is a ribbon footing?

A ribbon footing is another term for a continuous strip footing or a long discrete footing.

Conclusion for types of footing:

This types of footing is a foundation unit constructed in concrete under the base of a wall or column for the purpose of distributing the load over a large area.

In cold areas, the footing is placed below the frost line to prevent movement.

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