What are Fill Soils (Fill Dirt, Fill, & Foundation Settlement)

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We find many of our customers have issues with their foundation, specifically foundation settlement, due to improperly compacted fill soils.

We address foundation settlement via push pier installationhelical pier installation, and polyurethane foam injectionBut, the question remains – why do fill soils cause foundation issues?

Fills soils, otherwise known as fill dirt or fill, artificially change the grade and elevation of a property (typically where the foundation is laid).

We use the term “artificially” to specify this is not the original elevation or grade level.

Fill soils are utilized in new home developmentsconstruction sitesconstruction projects, and landscaping projects.

Fill soil is the reason we encourage buyers of new homes (built by companies such as KB Home and Lennar) to look for symptoms of foundation settlement:

Click on the link below to download our FREE printable checklist for foundation settlement symptoms –

Fill dirt is usually subsoil, aka the soil immediately underneath topsoil. Subsoil is comprised of a variable amalgamation of small particles like claysilt, and sand in addition to small rocks.

Clay is an expansive soil. Sand provides little in the way of strength and stabilization, which is why Jesus said build your house on rock. And silt, well, silt is just silty.

Fill should be free of organic matter as much as possible. Why? Organic matter decomposes, creating pockets of empty space within the fill.

Foundation Settlement 101 – empty spaces want to be filled and gravity is more than happy to oblige.

Empty spaces within the fill soilfill dirt, or fill cause settlement. Uneven or excessive settling can and will result in damage to whatever structure the foundation is supporting.

The great irony is fill soils can create spaces that need to be filled, which is where the magical properties of polyurethane can come in handy.

The irony is further compounded by the fact that any project that requires dirt to fill a hole or cavity (or raise/level the earth) is a good candidate for fill dirt.

Some of the most common projects that this soil is utilized for include:

  • Filling Voids/Holes
  • Leveling off embankments
  • Raising/Leveling Grade

To get even more specific, fill soil is also used for filling cavities or dips that cause flooding concerns and preparing grade for large paving projects (such as roadwayssidewalks, or even airport runways).

Smaller projects may include anything from prepping a backyard for a landscaping project, such as raised plant beds (upon which the final layer will be covered with a layer of more nutrient-rich soil to aid in proper growing) to

  • Leveling off land around pools
  • Leveling off land around patios
  • Leveling off land for home additions
  • Building up the ground, creating artificial height to prevent water drainage issues or securing the ground around retaining walls

What to do When the Fill Needs a Refill?

The primary issue with foundation settlement caused by fill soils is that the foundation is not sitting on competent load-bearing soil.

Once the foundation has been laid, it’s been laid – you can’t exactly dig the house up and throw more dirt under it. So, engineers rely on mudjacking and or polyurethane.

We’re pro poly and we cover why in our articlePolyurethane VS Mudjacking (weight, application, & cure time)

However, we also utilize steel pier systems that are covered by a lifelong warranty.

In this scenario, we put metal piers underneath the home, jack up the home to maximum practical recovery, and then fill the void.

We might not be able to fill the void in your heart, but we got the deep dark hole underneath your foundation.

Choose Dalinghaus for Foundation Repair 

We do foundation repair the right way. We believe in our process so much we have a lifetime warranty on all steel pier systems.

With over 100 years of combined experience and 4.9 stars out of 303 reviews – we are here to ensure that you never settle

If you live in SoCal or Arizona and would like a FREE foundation inspection, click the link below –


Brian Dalinghaus

Brian is one of the Co-Founders of Dalinghaus Construction. He has been in the foundation repair industry since 2005. During his career, he has been associated with helping over 4,000 homes and structures throughout California and Arizona.

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One Response

  1. A senior homeowner here. I had rainwater enter my unfinished basement where the wall meets the concrete floor. I need to grade around the foundation in the back and one side of the house. Is fill dirt the right material to use? What should I be asking for when buying the fill dirt? The topsoil sold at Home Depot and Lowes have other (organic) materials that will decompose through the years. I believe that is the cause of my problem now. I’m in NJ.

    Thanks in advance for answering this question.

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