Foundation Soil Guide – Know About Types of Soil for Building Foundation

Choosing locations with the ideal soil is an essential engineering decision in the construction process in both urban and rural areas. Your residence, duplex, or apartment is all associated with the soil. Your school, workplace, malls, and stores are all built on land. Hence, the soil,

 its type, and its qualities become very important. Let us explore various soil types for building foundations in this blog while also exploring the best-suited foundation for different soil types.

Why Is It Essential to Know Foundation Soil Types Before Construction?

Various kinds of soil will have varying effects on the foundation of your building. The type of soil on which a building stands impacts the project’s construction and long-term repairs. Knowing soil types will help you find the best soil for building foundations. It is important to lay foundations on solid and stable ground. The strength of soil varies; hence, some soils can support a skyscraper, whereas others cannot even support the weight of a person. If the soil beneath a building is unstable, the foundation may crack, sink, or even the building may collapse!

There are several well-documented research papers showing the evidence of structural damage resulting from a lack of soil knowledge. According to  (Sindelar, 2015), “One of the most famous is the Leaning Tower of Pisa. The land underneath seemed stable during the dry season when building began, but the soil became unstable during the wet season and sank under the weight of the building. Even worse, it sank unevenly, resulting in a leaning tower.” Additionally, (Muckel, 2004) says, “Information about soil properties provides a basis for assessing risks and hazards to buildings and other structures of human populations.”

     Popular Types of Soil for Construction

(1) Clay Soil

Clay soil is commonly found where rivers and streams once flowed, as well as where water seems to settle after heavy rainfall. Clay has smooth mineral materials and very little organic matter.

When wet, it is sticky, and it does not drain well. Because it is unstable, it is not the ideal soil for building a foundation.

Because of its tiny particles, it continues to expand and pushes against the foundation’s wall when wet. And as it dries, it shrinks, causing the foundation to shift. If not modified, it can cause cracks and uneven floors in a building.

To construct a foundation on clay soil, one must dig the field deeper to increase stability. A borehole bridge or a slab-on-grade foundation technique will make this the best soil for the foundation of a home.

A slab-on-grade foundation controls the soil’s tendency to expand and contract after construction, whereas a drilled pier foundation tends to increase structural firmness or stability.

Advantages of Clay Soil:

• Suitable for tropical environments
• Durable clay bricks add value as well as style to any home.
• Insulation properties help to reduce energy costs.

Disadvantages of Clay Soil:

• Awful foundation choice
• Extremely susceptible to dampness
• For proper use, clay soil requires skilled craftsmen

Recommended Best Foundation for Expansive Clay Soil:

1. Drilled pier foundation: Deeper anchors will provide more stability.
2. A slab-on-grade foundation: It can withstand the tendency of clay soil to shrink or expand.

(2) Peat Soil

Peat, or organic soil, is found in wetlands. It is dark brown or black in colour, has a strong odour, has a low bulk density, and is made up of decaying or organic materials.

It can support a few crops, but it is wet and vinegary, making it unsuitable for agricultural activities. During a dry period, peat soil can absorb a significant amount of moisture and become very dry.

It also has a high carbon content and when dry it feels like dry wood. This makes it highly flammable; once a fire starts, it is immensely difficult to put out. 

Due to its unstable nature, peat soil is one of the most challenging soils to build a structure or foundation on. This is because any structure built on it is prone to cracking, and other forms of damage in the long run.

Advantages of Peat soil:

• Environment Friendly.
• When used in walls, peat blocks act like an air cleaner.
• Peat blocks in the walls provide sound and thermal insulation.

Disadvantages of Peat soil:

• Poor selection for supporting structures
• Using peat correctly requires a high level of technical expertise.
• It can be difficult to find peat blocks.

Recommended Best Foundation for Peat Soil:

1. Replacing soil: When the peat layer is shallow, you can remove and replace it with engineered fills. This allows you to build over stronger soil while avoiding toxic gases during decomposition.
2. Concrete piles: Pad and beam foundations extend to a firm soil layer beneath. Learn about Pile Foundation.
3. Raft foundation: the absence of firm subsoil, you can support the structure with a raft foundation that extends beyond the peat soil.

(3) Silty Soil

This kind of soil can be spotted near rivers, lakes, and other bodies of water. It is composed of stones and other minerals.

When felt well with the hands, silt soil is very smooth and fine. It also has fine particles and can store moisture for an extended period. It contains significantly fewer particles than sandy soil, so moving currents can smoothly transport it.

Likewise, it has high fertility and is, therefore, suitable for farming. Nonetheless, because it stresses the structure, it isn’t good soil for constructing a foundation. Silt doesn’t really dehydrate quickly or easily when it holds water. As an outcome, it drains badly and expands, causing it to press up against the foundation. As a result, it offers only a minimal amount of structural support.

Advantages of Silty Soil:

• Fruitful soil
• Better water retention capacity
• It’s less difficult to work with that than clay.

Disadvantages of Silty Soil:

• It expands and weakens the foundation.
• Unsuitable for the majority of construction

Types of foundations recommended for Silty Soil:

1. Concrete piers: They can go down to the solid earth’s crust and the silt to support the structure without jeopardising its structural integrity.

(4) Loam Soil

This soil is ideal for building foundations. Loam soil, also known as agricultural soil, is ideal for planting. Most agriculturally successful areas have this soil.

As it contains sand, silt, clay, and humus and can also continue to maintain moisture and nutrients, it is the ideal and richest soil for crop planting. When compared to other types of soil, it also has a significantly higher calcium and pH level.

It provides suitable land for building a foundation due to its sand, silt, and clay constituents. It is the best combination for construction. As it absorbs and dries at a constant rate, loam soil handles humidity well. It also promotes proper airflow and drainage. However, cleansing it of decomposed organic particles or materials before establishing a structure on it is a must. This prevents future disasters.

Advantages of Loam Soil:

• It is ideal for construction because it holds water at a consistent rate.
• When used as a layer on the inside walls, it regulates air humidity.
• When combined with straw, it is ideal for building walls.

Disadvantages of Loam Soil:

• Only works in construction if organic or mixed soils are not used.
• Better than clay, but not as good as sand.

Recommended Best Foundation for Sandy Loam Soil:

1. Isolated pad footings: Based on the depth of the groundwater level, it would be ideal for loamy soil.

(5) Rock or Bedrock

Due to its high load-bearing capacity, river rock is an outstanding product for the construction of larger buildings such as skyscrapers, duplexes, and multistorey buildings. Rocks have a minimal risk of cracking or fracture formation in a building due to their high bearing capacity.

Granite, hard chalk, limestone, shale, and sandstone are examples of rocks. They have a lot of depth and stability. You can build your structure on any rock you want, but make sure it’s well-levelled before you start.

A bedrock layer refers to the layer of rock beneath the soil surface. It is composed of either igneous, sedimentary, or metamorphic rock. It is strong and resistant to water damage. This makes it an excellent choice for building.

Advantages of Rock or Bedrock:

• High load-bearing capacity
• Ideal for strengthening foundations
• Practical, affordable, non-toxic, and dependable

Disadvantages of Rock or Bedrock:

• Effective material only if levelled
• The right grain size does not naturally occur.

Types of foundations recommended:

1. Strip foundation
2. Pad foundation
3. Raft foundation

(6) Sand and Gravel

Sandy soil is created by the breakdown of rocks such as granite, quartz, and limestone. It lacks nutrients and is incapable of holding water. As a result, it is unsuitable for agricultural use.

Sand and gravel are good choices for building foundations because they contain large particles that help water drain quickly. This reduces the possibility of simply placing a building under stress.

Building stress results in both structural and non-structural cracks, which may also eventually lead to the building collapsing. To increase stability or support, one must compact both sand and gravel with some other better soil types, such as loam soil. For this soil type, screw piles or helical pliers are long-lasting foundation techniques. It keeps the soil from eroding and strengthens the foundation.

Advantages of Sand and Gravel:

• Supports heavy loads, making it ideal for construction.
• Provides adequate drainage
• It contains no organic or impure compounds.

Disadvantages of Sand and Gravel:

• Sand particles can wash away and leave gaps beneath the foundation.
• Quality sand is costly.

Recommended Best House Foundation for Sandy Soil:

1. Compact mix: Prior to pouring the foundation, the sand, and gravel mixture must be properly compacted.
2. Helical piers: While sand does not hold water, when water runs through it, it can lose its fraction and shift, leaving gaps beneath the foundation. Helical piers (also known as screw anchors) are an appropriate foundation for sandy soil in these cases.

Conclusion

Various types of soil to discover while constructing foundations are important to the construction of a house or other sort of infrastructure. There is no doubt that selecting an appropriate site for soil disposal is a significant technical decision during the construction stage in both cities and villages. Recognising several types of soil for building foundations enables us to determine whether they will have a significant impact on the project’s construction as well as long-term repairs. To experience the full benefits of various kinds of soil for house construction, make sure you select the correct soil characteristics for your home’s foundation. Consider the fact that different varieties of soil might have various impacts on the foundations of your project. This page discusses the most common types of soil used in foundation construction, as well as their benefits and drawbacks when paired with appropriate types of foundations. A multitude of elements influence the lifespan of a home, yet the type of soil in construction has an essential impact on the building’s life.

      Types of Soil for Building Foundation FAQs

01. Why is The Type of Soil Important When Building a House Foundation?

Knowing the type of soil is important because different soils require specific foundation types. For instance, peat soil often requires a raft foundation, while loam soil is well-suited for isolated pad footings. Choosing the correct foundation type ensures the strength, stability, and longevity of your house.

02. What Happens if The Soil Under a Foundation is Unstable?

Unstable soil beneath a building foundation causes foundation to sink, structural cracks in the building, or building may even collapse with time.

03. What is The Best Type of Soil for House Foundations?

Sandy soil is one of the best options for a house foundation. To increase its stability and support, sandy soil must be compacted with other soil types like loam soil.

04. Can Houses be Built on Clay Soil?

Clay soil has a property to expand when wet and shrink when dry, which makes it challenging for construction project. However, with proper treatment and foundation techniques, such as slab-on-grade or drilled pier foundations, it is possible to build stable houses on clay soil.

05. How do Engineers Decide Which Foundation is Best for a Specific Soil Type?

Engineers have knowledge of different types of foundation suitable for different types of soil. Hence, first know the soil type, then the loads to be transferred to soil, and lastly, recommend the best suited foundation.

Check out These Blogs Given Below for More Insights:

Importance of Topography & Soil Condition in Site Analysis

The Foundation in Black Cotton Soil/Expansive Soil Mystery Revealed

Soil Compaction: Ground Improvement Method Before House Construction!

Signs of Foundation Problems in Your House

References

Muckel, G. B. (2004). Understanding Soil Risks and Hazards. Retrieved from Natural Resources Conservation Services (.gov): https://www.nrcs.usda.gov/sites/default/files/2022-10/soil-risks-and-hazards.pdf

Sindelar, M. (2015, May). Soils Support Buildings/Infrastructure. Retrieved from Soils Support Buildings/Infrastructure: https://www.soils.org/files/sssa/iys/may-soils-overview.pdf