What is a Geotechnical Report and who cares?

13 Sep What is a Geotechnical Report and who cares?

A Geotechnical Analysis and Report often referred to as a “Soils Report” is as important as your foundation because it is the foundation of your foundation.  The process results in a detailed technical report of a Geologists Analysis of the soils under your home or building which is used to tell the design team an important story about the strength of the soil under the foundation.

The report is based upon one or more shallow borings, dug down to about 15 feet on your building site, preferably under the proposed foundation.  The soils from these borings are observed as they are dug and identified by soil type which gives the Geological Engineer the information, they need to determine the type and quality of soil on your building lot.

These samples are also lab tested for strength to determine the (bearing capacity) of the soil your foundation will sit on.  These values are indicated in PSF (Pounds Per Square Foot).  When the “Geo-Tech Engineer” is presented with the type of Structure to be built on the site including the number of floors and proposed foundation loads the Geo-Tech Engineer can then determine if the existing soil can support the weight of the proposed structure.  If not, the Geo-Tech Engineer will usually recommend a method to prepare or condition the soil to meet the require building load or will may also recommend a different type of foundation system that will carry the necessary load on the existing or modified soil conditions.

This is a very important point, please pay close attention.  If a Soil Report is not performed and supplied to your Architect and/or Structural Engineer, they will typically design the building foundation to bear on soil capable of supporting 2500 PSF.  When this occurs, and it is a common practice in the industry to do so, they will put a note on the plans indicating “ A Geotechnical Soil Report was not available (or not supplied) at the time of the design and the Owner is responsible to confirm the bearing capacity of the soil on site meets or exceeds 2500 PSF.”   This note puts 100% of the responsibility and liability on you the owner if a Geotech Report is not supplied or performed in the event of a structural failure due to a soils condition.

Beyond the science, the Geotech process can also be useful to determine if there is anything buried on the site which can vary from organics (buried trees, branches, or shrubs) which are a real problem for foundation support to environmental hazardous materials like batteries, lawn mowers or waste drums.

Another valuable test the Geotechnical Engineer can perform at the same time is a Percolation Test, which determines how fast the soil will absorb water.  This information is necessary if a septic system is to be installed and is also extremely helpful if there is a concern that the final site grading may potentially hold standing water.

One last advantage to having a Geotechnical Engineer do an initial soils investigation, you will already have an ongoing relationship when they will be needed for code required compaction tests.  Also, if fill is required it is highly recommended to have them test the soil at its source before it purchased and trucked onto your site to make sure it meets the design requirements.

For any questions contact me at 863-447-4100

Joe Papasso