Introduction When building strong, durable structures, one factor that makes…
Type of foundations
In construction, the foundation is where it all begins; it’s the backbone of a home or building. Proper foundation construction involves selecting the right type, preventing settlement issues, and preparing the subgrade correctly for the final curing stages.
What is Foundation in Construction?
In construction, a foundation is the lowest load-bearing part of a building or structure that allows the transfer of the structure’s weight safely to the ground. A foundation that is not constructed correctly can lead to cracks and shifts in the walls and floors, resulting in structural issues. Therefore, constructing an appropriate foundation for a residential home requires thorough planning, the right choice of materials and diligent execution at every stage. With the right techniques and materials, you can build a robust, long-lasting foundation that will support the house for decades.
Types of Foundation
The building foundation is the most crucial structural component in any house or building, as it bears the entire load of the structure and transfers it safely into the ground below. It forms the base that supports the overall weight of the walls, roof, floors, utilities and inhabitants of the home. Here are the two primary types of foundations:
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Shallow Foundations
Shallow foundations extend down to a depth of around 1.5 meters or less and are suitable for single-family homes and low-rise buildings. Here are some examples:
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Raft or Mat Foundations:
Shallow foundations that cover the entire building footprint. It is used when the soil is weak, or the building is too heavy for strip foundations.
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Strip Footings:
Long strips that support the entire weight of a wall. It is used in load-bearing masonry construction.
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Isolated Footings:
A common foundation type for residential structures, providing support to columns. It is used to distribute building loads to the soil.
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Combined Footings:
A combined footing is a single concrete slab designed to support two or more columns placed in a row. Instead of using separate isolated footings for each column, a combined footing distributes the loads from multiple columns into one unified structural element.
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Deep Foundations
Deep foundations go beyond 1.5 meters into bedrock or deeper soil. They are needed for multi-storied homes and buildings on weak or unstable soils. Deep foundations include:
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Pile Foundations:
Deep foundations that use columns (piles) driven deep into the ground. Piles can be standing or hanging, depending on how they interact with the soil.
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Caisson Foundations:
Large, watertight structures placed deep into the ground to support bridges and heavy structures.
The type of construction foundation depends on soil conditions, building loads and construction budget.
Foundation Construction Steps
Constructing a strong foundation ensures the durability of the building. For building a strong foundation, seven important steps are involved:
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Site Selection:
Ensure the ground condition is stable and not prone to frequent waterlogging. Consult with a structural engineer if necessary.
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Excavation:
Survey the land and mark pillar and trench locations before excavation to ensure accurate alignment and depth.
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Anti-Termite Treatment:
Protect the foundation from termite attack by treating the soil up to the plinth level.
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Compaction and Soling:
Compact the soil and add a layer of brick flat soling and lean concrete to create a firm base.
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Formwork Construction:
Set up a sturdy formwork to hold the foundation structure in place.
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Reinforcement Steel Work:
Use high-quality TMT rebar to reinforce the foundation, preventing cracks and weaknesses.
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Concrete Pouring and Curing:
Pour high-quality concrete, ensuring proper workability, compaction and curing to achieve maximum strength.
What Makes a Good Foundation?
A strong foundation is crucial for a long-lasting structure. A well-built foundation:
- Transfers structural loads evenly into the ground
- Withstands the effects of ground movement
- Made of high-quality concrete and proper rebar reinforcement
- Prevents cracks and settlement of the building
- Provides a strong, stable base for the superstructure
- Extends below the frost line to prevent damage from freezing
Required Tools for Foundation Construction
Having the right tools is essential for a smooth house foundation construction process. Some of the most commonly used tools in construction foundation include:
- Excavators and backhoes for digging and site preparation.
- Shovels and trowels for precise excavation and levelling.
- Concrete mixers to prepare uniform and high-quality concrete.
- Rebar cutters and benders for reinforcement preparation.
- Vibrators to remove air pockets and ensure proper concrete compaction.
- Measuring tape and levels to ensure accuracy in foundation depth and alignment.
Different Types of Foundation Tests
Ensuring the stability and load-bearing capacity of a foundation is important for the overall safety and longevity of any structure. Various tests are performed to evaluate foundations, which can be broadly categorised as follows:
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Soil Investigation Tests (Crucial Before Foundation Design)
These tests help characterise the soil properties to determine the appropriate type of foundation and its design parameters. Common soil tests include:
- Standard Penetration Test (SPT)
- Cone Penetration Test (CPT)
- Plate Load Test
- Shear Strength Tests (Direct Shear, Triaxial, Vane Shear)
- Compaction Tests (Proctor Test)
- Permeability Tests
- Moisture Content Tests
- Atterberg Limits Tests
- Chemical Tests: These identify corrosive elements in the soil that could impact foundation materials.
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Foundation Integrity Tests (Performed During or After Construction of Deep Foundations like Piles)
These tests assess the quality, strength, and structural soundness of the constructed foundation elements. Common foundation integrity tests include:
- Pile Load Tests: Static Load Test (SLT) and Dynamic Load Test (DLT)
- Pile Integrity Test (PIT) / Low Strain Integrity Test
- Crosshole Sonic Logging (CSL)
- Thermal Integrity Profiling (TIP)
- Parallel Seismic Testing
Note: The specific tests required vary based on the structure type, soil conditions, and foundation system being used. Hence, it is essential to consult a geotechnical engineer to define an appropriate testing program for any construction project.
Choosing the Right Cement for Foundations
Choosing the right cement is crucial for the strength and durability of your foundation. Here are some factors to consider:
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Bureau of Indian Standards (BIS) Certification:
Always look for BIS certification on the cement bags to ensure quality standards.
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ISI Certification:
Check for the ISI certification issued by BIS for quality assurance.
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Environmental Conditions:
Consider the environmental conditions the foundation will be exposed to.
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Cost-Effectiveness:
Choose a cement that balances strength and durability with your budget.
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Setting Time and Strength:
Consider the project timeline and choose a cement with appropriate setting time and early strength development.
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Compatibility with Admixtures:
If using admixtures, ensure the cement is compatible with them.
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Durability:
Choose from a wide range of cement types from JK Cement that offer longevity characteristics suitable for these conditions.
Besides the above foundation-specific tests, several tests on concrete and construction materials are also performed
Silt Test (Sand)
pH Test (Water)
Concrete Temperature Test
Sieve Test - Basic (Sand)
Slump Cone Test (Workability of Concrete)
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Frequently Asked Questions
The main function of a building foundation is to support and stabilise a structure by distributing its weight evenly to the ground, preventing uneven settlement and ensuring long-term stability.
JK Cement offers high-strength, corrosion-resistant and water-resistant cement solutions to build strong foundations.
Common testing methods include slump tests, compressive strength tests, rebound hammer tests, ultrasonic pulse velocity tests and ground-penetrating radar (GPR) to assess quality and integrity.
Foundation strength can be evaluated using visual inspection, soil tests, and concrete strength tests, such as the rebound hammer test or the ultrasonic pulse velocity (UPV) test.
