Comparative Analysis of Mat Foundation and Spread Footing in Construction

Introduction of Mat Foundation Vs Spread Footing

Mat foundation is also called a raft foundation. Generally, it is a continuous slab laying on the soil on which all the columns and beams of the structure are constructed.

By the mat foundation, all load of the building or structure is transferred to the soil. Where the soil condition is very weak there the mat foundation is used.

It is distributed all the load simultaneously to the soil that’s coming from the superstructure. For the basement, a mat foundation is very good.

On the other hand in the spread footing is provides for walls and masonry walls and the soil is removed from the trenches of the required size and the required depth.

After that in spread footing, 150 to 200 mm a bed concrete of mix 1:4:8 is provided. Over this bed of concrete, a stone masonry footing is built. In a suitable number of courses, the spread footing is built, projecting each course 50 to 75 mm from the top.

What Is Mat Footing?

The mat foundation is a continuous slab laying on the soil on which all the columns and beam of the structure are constructed. When the soil conditions under the foundation have not adequate strength to bear the load of the superstructure then the mat footing is provided.

It provides a perfect grip on the structure of the soil and prevents the tendency of overturning the building. It is provided when a large number of the floor are exited.

The mat footing prevents the sudden settlement of the structure. There are two types of mat footing – one is to a square shape and another is a rectangular shape.

The square mat footing is constructed to provide stability to the building. When a column is too close to the building or structure where mat footing is required. When two columns are so close to each other or they overlap each other where mat footing is necessary to provide.

The mat footing is constructed where there the strip footing or spread footing is not enough to bear the load that’s coming from the superstructure.

To distribute a uniform load from the superstructure to the subsoil mat footing is constructed.

What Is Spread Footing?

The spread footing is that footing in which it is provided for walls and masonry walls and the soil is removed from the trenches of required size and the required depth.

After that in spread footing, 150 to 200 mm a bed concrete of mix 1:4:8 is provided. Over this bed of concrete, a stone masonry footing is built. In a suitable number of courses, the spread footing is built, projecting each course 50 to 75 mm from the top.

Mat Foundation Vs Spread Footing

Different types of mat foundation vs spread footing that’s are below.

1. Mat Foundation and Spread Footing: Definition

Mat Foundation: A mat or raft foundation is a large slab supporting a number of columns and walls under the entire structure or a large part of the structure.

Spread Footing:  A spread footing (or isolated or pad) footing is provided to support an individual column. A spread footing is a circular, square, or rectangular slab of uniform thickness.

2. Mat Foundation Vs Spread Footing: Types

Both have many types that are follows.

Types of Mat Foundation.

There are six types of mat foundation that are-

1. Flat Plate Mat: A flat plate mat is used where the structure is lightweight and small. When the soil is not compressible where this type is suitable. In the form of the cage, the reinforcement bar is provided on both the top and bottom sides. At least 6 inches of RCC thick slab is provided in this type of foundation.
2. Plate Thickened Under Columns: When the upcoming column load is very heavy the slab thickness should be increased. Where the flat plate mat foundation is not enough to carry the heavy load that comes from the superstructure then the thickened plate foundation is connected. The heavy load creates a negative bending moment on the column and diagonal shear in the slab. So the thickness of the RCC slab under the column should be thickened.
3. Tow Way Slab and Beam: In a two-way beam and slab foundation, all beams are placed in a perpendicular direction, and each beam is connected to the slab foundation. And the intersection of the beam all columns are placed. This type of foundation suitable when the column is carrying an unequal load and between the column, the spacing is more.
4. Rigid Frame Mat: When the column has a heavy load then the mat foundation is used. In this type of foundation design, the basement RCC wall acts as a deep beam. When the foundation depth is required more than 90 cm then the rigid frame mat foundation is used.
5. Piled Mat Foundation: This type of foundation constructs in the soil by piles. Where the water table is near the ground level and the soil compressibility is high the piled mat foundation is suitable for those places. Where the high-rise building is constructed the piled mat foundation is used.
6. Cellular Mat Foundation: The cellular mat foundation has also termed a box mat foundation. A box type of structure is formed whose wall acts as a beam. The walls are both sides top and bottom are connected by the slabs.

Types of Spread Footing

There are six types of spread foundation that are

1. Wall Footing: The wall footing are two types one is simple and another is steeped. The steeped is used for heavy load and simple is a light load.
2. Isolated Footing or Column Footing: To supported individual columns the spread footing is constructed. The isolated footing can be a slab, slope, or stepped type.
3. Combined footing: The combined footing is constructed when two or more column is supported in a row. The shape of the combined column is either rectangular or trapezoidal.
4. Strap footing or cantilever footing: When connected by a beam two or more individual footing is called strap footing. The other name of this footing is cantilever footing.
5. Continuous footing: To required supported two or more columns in a row a single RCC slab is provided that is called continuous footing. In the earth quick area, this type of footing is suitable.
6. Grillage footing: Where the soil has low bearing capacity the grillage footing is used to transfer a heavy load from the steel structure. This type of footing is very economical for construction.

3. Mat Foundation Vs Spread Footing: Construction

 Mat Foundation Construction

The mat construction process is very important in which extra care should be needed. The few processes of mat foundation are described below.

1. Soil Excavation for Mat Foundation: The excavation of soil for the foundation is more important because it provides a plane surface for the foundation. The excavation depth depends on the bearing capacity of the soil.
2. Waterproofing:  All the mat foundations are generally waterproofed. When it is construed at the ground level waterproof, the membrane is added. That makes it waterproof. For this, the foundation is always protected from wetness or dampness.
3. Mat Foundation Reinforcement: Generally, there are two types of reinforcement is provided in the mat foundation one is bending reinforcement and another is shear reinforcement. The shear reinforcement is provided in the column and bending reinforcement provides as usual.

Spread Footing Construction

In spread footing to the required depth, excavation is done. After that, the bottom of the excavation is compacted and leveled. The arches to be constructed under the piers to finished according to the layout. At last, to take the outward thrust caused by arch action, the end piers should be designed and constructed.

4. Mat Foundation Vs Spread Footing: Uses

Uses of Mat Foundation

The uses of a mat foundation.

1. Where the soil bearing is very poor and the soil does not bear the load of the structure then mat foundation is used.
2. When a column is near the building or property line then mat foundation is used.
3. When the distance of the two columns is very less than the mat foundation used.
4. When the depth foundation cost is more than that of the shallow foundation then the mat foundation is used to reduce the cost of the structure.

Uses of Spread Footing:

1. The uses of spread footing are to reduce the cracking caused by settlement.
2. The advantage of spread footing is by this footing around the base makes the soil stabilized.
3. The most important use of the spread footing is that by this we can make a stabilized structure.
4. In the spread footing, the basement can easily construct.
5. In this spread footing the design of the structure and the quality of the structure can be easily controlled for this it is widely used in construction.

5. Mat Foundation and Spread Footing: Advantages

This both have many advantages that are follows

Advantage of Mat Foundation:

1. It has good resistance for this the building can not slide during the flood.
2. The mat slab foundation can help transfer the load of the building to a verse area.
3. To make an economical structure like when the cost of depth foundation is more than from the shallow foundation then we constructed a mat slab foundation.
4. In this mat slab foundation, we can reduce the materials cost because when we construct the foundation at the same time the ground floor slab is poured for this reason the time and materials both are safe.
5. The mat slab is a shallow foundation for this the depth of the foundation is less so the excavation for the foundation is less.
6. The mat slab foundation can take more than load from the other type of foundation.
7. In another advantage is that the mat slab foundation can construct in poor soil.

Advantages of Spread Footing:

1. The advantage of spread footing is to reduce cracking that caused by settlement.
2. In the spread footing, the basement can easily construct.
3. The advantage of spread footing is by this footing around the base it makes the soil stabilized.
4. The most important advantage of the spread footing is that by this we can make a stabilized structure.

6. Mat Foundation and Spread Footing: Disadvantages

Both have many advantages that are follows.

Disadvantage of Mat Foundation:

1. It has some disadvantages that are –
2. The number of quantity materials like steel or concrete required more for the mat foundation.
3. The mat slab foundation is not suitable for domestic uses.
4. In the case of concentrated loads, sometimes a special measurement is needed.

Disadvantage of Spread Foundation:

1. The common disadvantage of spread footing is it is not suitable for all types of soils.
2. The disadvantage of spread footing is that it should be a built-in number of courses and each course should be projected 50 to 75 mm from the top course.
3. Another disadvantage of spread footing is the construction area is required more for this footing.

FAQ: Mat Foundation vs. Spread Footing

What is a mat foundation?

A mat foundation, also known as a raft foundation, is a large continuous slab that supports multiple columns and walls under an entire structure or a significant part of it. It distributes the building load uniformly across the soil.

When is a mat foundation used?

Mat foundations are used when soil conditions are weak and cannot bear the load of the superstructure, when columns are closely spaced, when a basement is required, or when the depth of a traditional foundation is too costly.

What are the types of mat foundations?

The six types of mat foundations include:

1. 1. Flat Plate Mat
   2. Plate Thickened Under Columns
   3. Two-Way Slab and Beam
   4. Rigid Frame Mat
   5. Piled Mat Foundation
   6. Cellular Mat Foundation

What is spread footing?

Spread footing, also known as isolated or pad footing, supports individual columns. It consists of a circular, square, or rectangular slab of uniform thickness that spreads the load over a larger area of soil.

When is spread footing used?

Spread footing is used for supporting walls and masonry walls, stabilizing soil around the base, reducing cracking caused by settlement, and facilitating basement construction.

What are the types of spread footings?

The six types of spread footings include:

1. 1. Wall Footing
   2. Isolated Footing or Column Footing
   3. Combined Footing
   4. Strap Footing or Cantilever Footing
   5. Continuous Footing
   6. Grillage Footing

What are the construction steps for a mat foundation?

The key steps include soil excavation to provide a plane surface, waterproofing the foundation, and reinforcing with bending and shear reinforcements.

What are the construction steps for spread footing?

The construction involves excavating to the required depth, compacting and leveling the excavation bottom, constructing arches under piers, and designing end piers to handle outward thrust.

What are the advantages of a mat foundation?

Mat foundations provide good resistance against sliding during floods, efficiently transfer loads over a large area, are economical when depth foundations are costly, reduce material costs, and can be constructed on poor soil.

What are the advantages of spread footing?

Spread footing reduces settlement cracking, stabilizes soil, facilitates easy basement construction, and ensures a stable structure.

What are the disadvantages of a mat foundation?

Mat foundations require a large quantity of materials, may not be suitable for domestic use, and might need special measures for concentrated loads.

What are the disadvantages of spread footing?

Spread footing is not suitable for all soil types, requires multiple construction courses with specific projections, and demands more construction area.