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What is Fill Dirt?

Fill dirt is the unsung hero of landscaping and construction, providing a stable base for projects. It's earthy material, typically subsoil, free from organic matter that could decompose and cause settling. Ideal for creating foundations or leveling ground, fill dirt ensures your structures stand firm. Wondering how it can transform your outdoor space? Let's examine its potential together.
Rhonda Rivera
Rhonda Rivera

Fill dirt is used to fill holes or build up ground in construction projects. This type of dirt is usually subsoil, also known as substrata, which is a material found under topsoil. It is basically partially broken down soil that contains clay, sand, and other materials. Fill dirt is typically obtained when a construction project requires the workers to dig a deep hole and begin the construction there. The subsoil is removed from the site and kept for later use or sold or given away to another individual or company who can use it.

A popular use of fill dirt is to build up ground before constructing a building to reduce the chances of flooding. This is normally done when the construction site is low-lying, and the area receives enough rainwater to potentially flood the to-be-constructed building. Fill dirt has been used in this manner before the construction of everything from airports to homes. This type of dirt has even been used to help create man-made islands. Other smaller-scale construction projects that use fill dirt are usually performed by a landscaper to build waterfalls, pools, or just provide a more interesting texture to the landscape.

Fill dirt is found under topsoil and contains clay, sand, and other materials.
Fill dirt is found under topsoil and contains clay, sand, and other materials.

Another common use of subsoil is highway maintenance. The area surrounding a road can gradually erode due to rainwater, people parking on the roadside because of car trouble, and other factors. When this happens, the roadway maintenance authority might pay for the sides of the road to be built up in order to make it safer for drivers to pull over.

There is generally an abundance of fill dirt no matter the region, so the material is inexpensive. If the buyer cannot pick up the dirt, however, the costs of delivery can significantly increase the price. For example, it is not unusual for delivery alone to be three to five times the cost of the dirt. This does not factor in the cost of spreading the dirt, however; most companies that sell fill dirt do not spread it, only sell and possibly deliver.

Fill dirt is not only used for large construction projects; individuals building up their backyard for various reasons sometimes use the dirt. In some cases, the individual can simply call a few construction companies to ask for free dirt. This can sometimes save a lot of money, but it is necessary to have a vehicle capable of moving the dirt. The construction company is doing the individual a favor by giving him or her the dirt; they likely will not deliver it too.

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Discussion Comments


@Cageybird, I know what you mean about the importance of "clean" fill dirt. One of my college theater professors decided he wanted to use real dirt on a backyard set. He called a local company that provided fill dirt for construction sites. A truck delivered two tons of fill dirt to the theater and we spread it over the set. Two days before the play opened, I walked into the theater and smelled insecticide everywhere. It turned out that the fill dirt was not as "clean" as advertised, and it still had a fire ant nest.

The next time he staged a play using real dirt, he invested a lot more money in genuine topsoil from a plant nursery. Fill dirt was just too risky around people.


One thing to keep in mind is that all fill dirt is not alike. Some providers offer "clean" fill dirt, meaning elements like rocks, insect nests and plant roots have been removed. This might not make much of a difference when filling in a deep construction hole, but if the fill dirt will be spread out on the surface of a park or farmland, then these things could become hazards. Clean fill dirt may cost more than the unfiltered kind, but it might be necessary for certain projects.

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    • Fill dirt is found under topsoil and contains clay, sand, and other materials.
      By: godunk13
      Fill dirt is found under topsoil and contains clay, sand, and other materials.