Knowing the different types of dirt in the ground and how to use each type is critical for the success of any construction project. While it might not seem like a big deal to the uninitiated, using the wrong type of dirt could cause a structure to crumble because it doesn’t have the support it needs.

Understanding how to differentiate fill dirt (or clean dirt) from topsoil is especially important.

Various Types of Fill or “Clean” Dirt

The term fill dirt refers to dirt that covers holes or helps to build elevation at construction sites. Subsoil is a type of fill dirt found 12 inches below the earth. Fill dirt can contain various substances when it originates from a woodland or farm. Some types of fill dirt contain organic materials, but most do not.

This makes fill dirt ideal because it doesn’t settle or decompose quickly as dirt containing organic materials often does. Another benefit of fill dirt is that it’s inexpensive. Here are the most common subcategories of fill dirt:

  • Clean fill dirt: The word clean doesn’t refer to the dirt but the fact that it contains no contaminants such as combustibles or corrosives. Clean fill dirt also doesn’t have glass, wood, or other types of debris mixed into it. Typical uses for clean fill dirt include leveling a construction area, improve drainage, or changing the elevation of the land.
  • Certified fill dirt: Any individual or company can sell clean fill dirt, but that doesn’t guarantee the customer will bring clean fill dirt home. Unfortunately, organic dirt can cause a significant safety issue when it starts sinking into the earth during a construction or landscape project. Finding a reputable supplier that labels bags as certified fill dirt is the best way to avoid this problem.
  • Septic fill dirt: Made exclusively to fill in the open area around a septic tank, septic fill dirt typically contains concrete or manufactured sand. Septic fill dirt doesn’t retain moisture, which means the land around it won’t settle or clump. It can be especially effective to use septic fill dirt on property that sits at a high groundwater level or to help a water tank drain more efficiently. Construction workers often use this type of dirt to level out areas they will later pave.

The Role of Topsoil

Topsoil differs considerably from fill dirt. First, it contains organic materials and healthy nutrients taken from the soil’s top layer. People use topsoil to support vegetation rather than use it to fill holes in the ground. Topsoil is easy to differentiate from fill dirt because it’s darker and lighter.

Most topsoil has a mixture of organic materials. It should not contain any lumps, sticks, roots, or rocks for maximum effectiveness. Any of these materials can affect the purity of the dirt.

It might seem like all dirt looks the same, but that’s just not true upon closer inspection. Choosing the right type of dirt and using it as intended can make all the difference between a successful construction project and one that fails.