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Why You’ll Want to Get a Soil Test Done Before Building a New House

An Overview of How Soil Testing is Done

Soil engineers take soil samples by boring holes in the ground. Samples from shallow bore holes as well as bores taken from seven to ten feet below the surface are collected. Typically engineers take between four and eight soil samples, in order to test the water table and to test for bedrock or harder soils. How many samples are taken will vary depending on the size of the project and the land site as well as the soil engineer. Although the test results are usually more accurate when more samples are collected.

Soil samples testing is done by laboratories with expertise in determining whether the soil is suitable for construction. Laboratories identify all of the compounds in the soil, they look for potential problems that could be caused by soil composition and they test for a wide range of pollutants. If dangerous pollutants are present, a plan for mitigation of those pollutants must be enacted.

Why Soil Testing is Important Before Construction

Soil testing for home building, both new construction of homes and apartment/condominium complexes is necessary for several reasons. First, quantification of soil composition is important in determining whether the site can properly support the foundation it needs. Second, testing the soil for potential pollutants ahead of time will identify if the soil is safe to build on and will save builders from dealing with pollutants that may show up during excavation which produces delays, mitigation costs and other troubles. Third, soil testing for home building is usually required to get a building permit.

If the soil is too loose, easily compressed, oversaturated or contains high amounts of absorptive clay then special construction accommodations may be needed. This does not mean that the land cannot be built upon, but it does mean that extra foundation supports such as the replacement of bad soil and/or wider or deeper foundations could be necessary. The problem with failing to provide extra foundation support is that cracked and crumbling foundations can result from the expansion and contraction of soil due to moisture content, freezing and thawing. Damage like this can only be fixed by costly foundation repair.

When Should Soil Testing Be Done?

Soil testing for construction is typically performed after the foundation has been dug but prior to the footings being placed. However, sometimes soil testing for pollutants must be done either before any digging occurs (because of known pollutants in the same area) or after digging begins because odors or other indications reveal the presence of pollutants.

It is also common to request a soil test before land purchase and to put in writing that any offer is contingent upon the property passing a soil test for building. Soil testing is often ongoing throughout the construction process. One thing to consider is that soil samples testing during the buying and pre-construction phase, before digging begins, is more expensive than after the foundation has been dug.

Who Does Soil Testing?

Soil engineers most often collect soil samples and work with environmental laboratories to do the soil samples testing. Soil engineers can be hired privately and are also known as geotechnical engineers. A soil engineer must hold a degree in civil engineering, be licensed in the state and have passed the National Council of Examiners for Engineering and Surveying (NCEES) Fundamentals of Engineering examination. Many of them work with testing laboratories to get their soil test results.

When looking for an environmental testing laboratory that does soil testing for home building, it is important to find one that has a long and distinguished record of high quality testing results. It is also important that the laboratory has continually invested in the most up to date technology and testing equipment. If turnaround times (TATs) are very important then it will be important to ask what is their record for TATs and if they offer rushed services.

What Can You Expect from Your Soil Test?

Soil engineers often test the soil before, during and after construction in order to ensure full compatibility throughout the process. Laboratories will provide detailed reports for any and all tests that soil engineers order. Make sure that a clear explanation of the results is given by the engineer, the laboratory or ideally both of them. After identifying the soil composition, soil engineers will recommend the best ways to overcome whatever issues exist. These solutions can include soil grading, increased drainage, bolstering foundations and creating earth supports.


When doing any kind of soil test for building, it is important to know who to contact, what can be expected, why soil samples testing is important and how to deal with the results. Torrent Laboratory offers advanced sampling, testing and reporting methodology for air, water and soil analysis. Our chemists perform all Volatile Organic Compounds (VOCs) analysis with next-generation Gas Chromatography and Mass Spectrometry systems. Our lab boasts the most highly-automated extraction capabilities in laboratory analysis for Semi-Volatile Organic Compounds in Northern California. Torrent Laboratory gives you the data you can trust—fast.