What Is Select Fill? (And When to Use It)
Select fill is an engineered, low-plasticity granular soil placed in compacted lifts to build stable, load-bearing grade under slabs, pads, and pavements. On structural work it is the fill you order when ordinary dirt is not good enough.
Key takeaways
- Select fill is a specified material with controlled gradation and low plasticity, not generic dirt. It is sourced to a written standard such as TxDOT Item 132 embankment (Type A granular) and screened against the IBC expansive-soil threshold.
- It differs from fill dirt and common fill mainly in plasticity, gradation, and how predictably it compacts. Select fill is the structural option.
- Use it where the soil carries a structure or pavement: building pads, foundation subgrade, and load-bearing grade. Verify it with lab testing (Atterberg limits, Proctor, compaction).
A clear definition of select fill
Select fill is imported soil chosen for its engineering behavior rather than convenience. The goal is a fill that compacts to a high, repeatable density and does not shrink and swell with moisture. In practice that means a granular material with a low plasticity index and a clean gradation, placed in thin lifts and compacted to a target density. We supply it as a commercial material for contractors, civil and site-work crews, and developers across DFW, Austin, San Antonio, and Houston. You can see specs and order it on our select fill page.
The word “select” is the key. The material is selected against criteria. That is what separates it from soil that is simply moved off a different part of the site.
Select fill vs fill dirt vs common fill
These terms get used loosely, but on a structural job the differences matter. The table below frames how the three materials are typically specified and used.
| Material | Plasticity and gradation | Typical use |
|---|---|---|
| Select fill | Low plasticity, controlled granular gradation, spec-driven (e.g. TxDOT Item 132 Type A) | Building pads, structural subgrade, load-bearing grade |
| Common fill | General-purpose fill, looser tolerances, compactable but less controlled | Bulk grade raising, backfill, non-structural areas |
| Fill dirt | Native subsoil, often higher clay content and higher plasticity, variable | Rough grading, filling holes, landscape volume |
The shorthand: fill dirt is whatever earth fills a void, common fill is reasonable general-purpose fill, and select fill is the engineered material you put under something that has to stay put.
What standards select fill is sourced to
Reputable select fill traces back to a written specification. In Texas the common reference is TxDOT Item 132, Embankment, which defines Type A as a granular material that meets a short list of testing requirements. The caps below exist because plasticity drives shrink-swell movement, and low-plasticity material moves far less, which is exactly what you want under a structure built on Texas expansive clay.
| Item 132 Type A property | Test method | Specification limit |
|---|---|---|
| Liquid limit (LL) | Tex-104-E | 45 or less |
| Plasticity index (PI) | Tex-106-E | 15 or less |
| Bar linear shrinkage | Tex-107-E | 2 or greater |
Those are the published Type A limits, verified by standard Texas test methods. The liquid-limit and plasticity-index caps keep the material from shrinking and swelling; the minimum bar linear shrinkage keeps just enough fine content for the fill to bind and compact rather than ravel. Many project specs reference these numbers directly or tighten them in the geotechnical report.
We source select fill to these documented standards rather than to a single number we promise. Plasticity, gradation, and compaction targets are set by the project geotechnical report and the specifying engineer, and the material is tested to confirm it meets them. Because Soil Depot is a young company, we earn trust through spec compliance and test data, not tenure claims.
Where select fill is used
- Building pads: a compacted select fill pad gives a slab a uniform, low-movement base.
- Foundation and slab subgrade: structural fill replaces unsuitable native soil beneath footings and grade beams.
- Load-bearing grade and pavement subgrade: stable support for drives, parking, and equipment areas.
- Structural backfill: behind walls and around structures where settlement must be controlled.
How select fill is tested and verified
Verification happens in the lab and in the field. Atterberg limits (ASTM D4318) measure liquid limit and plasticity index to confirm the material is low-plasticity. Classification (ASTM D2487, USCS) confirms it falls in an acceptable soil group. A Proctor test establishes the maximum dry density and optimum moisture, using standard effort (ASTM D698) or modified effort (ASTM D1557) per the spec. In the field, crews place the fill in lifts and a technician confirms each lift reaches the required percent of that Proctor density before the next lift goes down. On TxDOT-referenced work, Item 132 places embankment in lifts no thicker than 12 inches compacted, and for low-plasticity material (PI of 15 or less) it requires a field density of at least 98 percent of the maximum dry density established by Tex-114-E, checked in place with Tex-115-E. That is the difference between fill that is simply dumped and fill that is engineered: a documented density on every lift.
How to order select fill
Have your plans, the geotechnical report, and any required spec on hand so the material matches what the engineer called for. Size the order with our soil calculator, or walk through the math in our guide on how much fill dirt you need, confirm delivery to your metro on the service areas page, and send the details to our team. We will match the right material to the spec and schedule delivery.
Select fill FAQ
Need select fill on a job site?
Tell us your spec and volume and we will match the material and schedule delivery across DFW, Austin, San Antonio, and Houston.