When do you need a soil test?

March, 31 2020

Construction projects take a great deal of time, planning and effort. One of the most important steps in the early stages of a new construction project is having the soil tested. Keep reading for more information about what soil testing is, when it needs to be done, and why it is important.

What is a soil test?

Simply stated, it checks to see what the soil is made up of at a given site. A geotechnical engineer will extract samples from different spots and at different depths on the site, then analyze them to determine the soil’s composition and classification.

Materials are not the only factors used to decide how the soil in certain places is classified. Other factors include proximity to sources of vibration (like roads with heavy traffic), how recently the site has been disturbed, and signs of water seeping into the ground.

OSHA classifies soil composition into three categories:

• Type A (most stable): cohesive materials like clay, sandy clay, silty clay, and clay loam. They stick together and can withstand heavier loads placed on top of them.

• Type B: cohesive materials like angular gravel, silt, and soils that are fissured or located near sources of vibration (and would be Type A otherwise). They can hold up moderate loads.

• Type C (least stable): granular materials like gravel, sand and soil with water seeping through it (regardless of other characteristics). These materials do not stick together very well and can only withstand lighter loads placed on them.

When it needs to be done

In construction, soil testing is completed in the preliminary planning stages of a project. The sooner it is done, the better.

Why is it important?

There are three reasons why this is important as part of the construction process.

One – before anyone considers doing something with a specific location, they need to be aware of what will be underneath whatever is built. The results can help determine the feasibility of the site in question early on.

Two – soil composition is important information for the architects and engineers who design the building to have. They should know how reactive the soil is (meaning how likely it is to move, expand, or contract) and what the conditions are on-site. If they have been made aware, they can account for some of the conditions on the materials and methods they incorporate into the plans they propose.

Three – depending on where the site is, you may find it necessary to submit the results as part of the approval process. It is usually included with the initial submittals to city or county officials.


Soil testing is an integral part of starting work at a new location. Choosing the right soil consultant will help your project get off on the right foot. Contact us and maximize the productivity and profitability of your projects in Southern California by supporting it with our geotechnical and geological experience.

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G3SoilWorks – a full service geotechnical / engineering geologic consulting firm, is pleased to reach our third year. It has come with many interesting clients, assignments and obstacles.

350 Fischer Avenue Costa Mesa, CA 92626

Tel. 714-707-3155
E. info@g3soilworks.com