Skip to Main Content

Soil Layers

When building or remodeling your home, it’s essential to understand the kinds of soil beneath its foundation. Here’s what you need to know.

Get a Free Estimate

The process of constructing a building is a long and complex one. No matter if you’re building a modest family home or a multi-floor commercial building, you will be doing lots of planning and preparation to reach your desired result. And since we build our structures from the ground up, the first thing the construction crew needs to do is lay down the foundation. 

However, building your substructure requires previous knowledge about the soil that will be beneath it. If you don’t give it much thought, chances are that you’ll face foundation problems even before the building process is over. 

Read on as we provide you with information about the most common soil layers. We’ll also cover their pros and cons, as well as their physical attributes.  

soil layers under homes

What Are Soil Layers? 

Before we start describing each soil layer, it’s important to explain what soil layers actually are. That said, soil layers are deposits that form over a long period of time. They consist of various materials such as rocks, clay, and sand. A soil’s load-bearing capacity and potential for stability are rooted in these soil layers and their constitution at a particular site. 

Several factors affect soil layers and their physical properties. They include wind, water, glaciers, and even human activities such as construction. As soil layers form over time, they gain in strength and capacity to bear weight. Beneath these layers are inert types of soil — bedrock — that consists of hard rocks that don’t compress or shift. 

Types of Soil Layers 

Fill Soil 

Frankly, there’s a lot of construction going on these days. As such, quality soil to build on is harder to find in urban areas. This means that builders sometimes need to move new soil to the construction site before they can begin construction. 

This is what we refer to as fill soil. Some people call it man-moved soil, which is very self-explanatory. Either way, it is used to fill the holes and depressions in the ground. It is then flattened out and made ready for the foundation. 

You can differentiate three types of fill soil: 

  • Engineered fill soil: Consists of granular materials or select subgrade soils and can provide enough support for a foundation. 
  • Dumped fills: This fill soil is not perfect, but it can still do a good job if you use it properly. Dumped fills will provide support since they have less gravel and stones in them. 
  • Hydraulic fills: Using water streams, builders can move soil from one area to another. Hydraulic fills include select particles of heterogeneous soil and deleterious materials. 


Bedrock or load-bearing strata, as some call it, is a layer beneath some other type of soil. It consists of hard rocks and other sturdy materials. It is perfect for carrying huge loads because it doesn’t shift or compress. Also, it doesn’t settle, sink, or even crack, making it ideal for heavy buildings with numerous floors. 

Experts call it “non-active soil”, which means that bedrock is inert. Unlike silty sand or clay soil, it doesn’t expand or contract. These rocks are usually limestones or sandstones, as well as some other types. Bedrock is stable no matter what kind of weather affects it. But before you can begin construction on it, builders must level it. 

If the layer over the bedrock is soft, you’ll need deep foundations. In this case, the bedrock needs to be at a reasonable depth, between 60 and 200 feet. These deep foundations support heavy loads of large structures. They come in different types such as pile, caisson, basement, hollow box, and shaft foundations. Their capabilities vary, meaning the process of installing them does too. 

Glacial Deposits 

Glacial deposits form from particles of minute clay and large boulders in areas where there is a glacial mass. Sometimes, builders also call these deposit drifts. 

Glacial deposits consist of rock fragments that come along icy paths. Frozen, icy formations such as glaciers move, and when they stop, things they picked up along the way begin to decay. The remains of these glaciers end up on the land surface. Running water picks them, and they find themselves alongside lakes and rivers. 

The deposits usually come in the form of gravel, clay, or other organic materials. Either way, they vary in size. And if you’re looking to lay down a foundation over it, it’s essential to determine which type of glacial deposit soil it is before construction begins. 

Erosion Soil 

Unfortunately, soil is prone to erosion. Flowing water, wind, and ice will constantly disrupt it by removing the top layer from the profile. By disrupting the soil on the horizon, erosion will cause weathering. The soil will lose essential nutrients, particles, and organisms that keep the layers together. 

Erosion is pretty detrimental to your home’s stability. It will disrupt your foundation, causing numerous problems such as cracks and fractures across the whole structure. But what makes it so dangerous is the fact that it can occur over a long chunk of time, leaving you without a clue about what’s going on. 

There’s no need to say that erosion soil is bad for construction. Without its nutrients and microorganisms, it is unstable and weak. You can’t even use it as fill because its properties will remain the same no matter where you move it. It’s frail and won’t hold a structure in place. 

Foundation Repair 

If you’re having problems with your foundation due to the soil underneath it, we suggest that you immediately contact professionals. Our crew at AFS will provide you with a free inspection of the situation. Afterward, they’ll provide you with solutions that will make your home stable once again, as well as a free estimate regarding the cost of repairs.

Publish Date:

Last Modified Date:

AFS Coverage Map


Birmingham, AL

130 Interstate Commerce Crt. Bldg. 100 & 200
Alabaster, AL 35007

Chattanooga, TN

214 Industrial Park Dr.
Soddy-Daisy, TN 37379

Columbus, GA

2701 Opelika Road
Phenix City, AL 36870

Huntsville, AL

2415 Jordan Road
Huntsville, AL 35811

Knoxville, TN

3028 E Governor John Sevier Highway
Knoxville, TN 37914

Mobile, AL / Biloxi, MS

3131 Hamilton Blvd.
Theodore, AL 36582

Montgomery, AL

445 Dexter Avenue, Suite 4050
Montgomery, AL 36104

Nashville, TN

1519 Heil Quaker Blvd.
LaVergne, TN 37086