Soils inspections are often neglected by owner-builders, and yet, they play a crucial role for years to come after a home is constructed.
In this post, we’ll explain what soil inspections are, how they’re performed, and why they’re an essential part of planning your new home’s construction. Read on to learn more.
Why are Soil Inspections Important?
Soil is the medium that supports your home’s foundation, effectively carrying the weight of the entire building. A soil test exposes the subsurface conditions beneath the intended building’s footprint and lets you and your project team know whether:
- The soil is strong enough to bear the weight of a foundation without additional supports
- High water table or erosion is a threat to the soil’s ability to support the building
Apart from revealing these important soil conditions, a soil investigation may expose contaminants and circumstances that may affect seismic design.
Soils reports are also typically required by your local building department when you apply for a building permit.
Soil Density and Expansive Soils
The primary goal of soil testing is to establish whether the soil on which you’re building a new home has sufficient bearing capacity to support the structure.
Weak soils undergo excessive compression when under pressure, which means they can’t adequately support the weight of the home, and the home’s foundation may settle unevenly. This eventuality can lead to major foundation damage as time goes by, and the ensuing repair costs can be stunningly high.
Another common issue with some expansive soils, such as clay, is their tendency to expand and contract in response to moisture, heat, and cold. This property translates into frequent sinking and heaving — motions that place undue stress on the home’s foundation and eventually lead to damage and expensive repairs.
A soil investigation can pinpoint issues with soil density and absorption so the project’s engineers can design appropriate supports for the foundation.
Water Table and Susceptibility to Erosion
A soil investigation can determine the water table levels beneath the soil. This determination will influence your home’s below-grade design; for example, a high water table could mean that building a basement is simply impractical.
If your lot is on a hillside, a soil investigation can assess the ground’s propensity to erode due to rainwater flow. Severe erosion could lead to landslides, which is a substantial hazard to any hillside building. To this end, the soil test results could show which erosion control measures would be required to ensure your new home’s safety. Alternatively, if the erosion hazard is too grave, you could choose to forgo the land purchase and look for a different lot.
How is Soil Testing Performed?
During a soil inspection, a soil (or geotechnical) engineer bores holes at random locations on the construction site and collects soil samples from them.
The depths of the holes will vary depending on the project’s location and known soil conditions. For instance, if shallower holes reveal soil with extremely poor bearing capacity, the engineer may want to bore deeper to determine where the bedrock is. This depth will be crucial in planning the adequate foundation supports, which may have to rest extended down to the bedrock.
Once the samples are collected, the engineer sends them to a geotechnical lab for analysis.
Who is a Soil Engineer?
A soil, or geotechnical engineer, is a professional who specializes in investigating various soil conditions and assessing their effects on human-made structures and systems, such as foundations, erosion control, and various civil works.
In California, soil engineers are licensed civil engineers who undergo specialized training and examinations before being allowed to practice under the title “geotechnical engineer.” Only certified geotechnical engineers are allowed to produce soils reports.
Do I Need a Soil Test?
Your local building officials may require a preliminary soil investigation for any new building and process your permit application only if it contains a soils report. If you’re planning on building a new home, it may be wise to ask your building department if getting a soils report is mandatory.
However, even if a soils inspection is not officially required, the benefits of performing one on your site may outweigh its relatively small costs. Here’s what a soil inspection can do for your project:
- Detect harmful subsurface conditions — These may lead to severe foundation damage and enormous repair costs.
- Establish the water table — Doing so may help you avoid water and moisture issues.
- Expose contaminants — The soil may contain substances that are hazardous to human health.
- Help avoid erosion and landslides — If you’re building on a hillside, a soils report will dictate the necessary retention methods to safeguard a hillside home from erosion.
What a lot of people don’t realize is that a soil inspection can actually help you save money. That’s because soil reports give your structural engineers a clear idea of what the subsurface conditions are, so they’re not forced to over-design and add unnecessary costs to the construction budget.
How Design Everest Can Help
If you’re building a new home, a soil inspection should be one of your priorities — especially if you want to avoid costly foundation damage and moisture issues.
Design Everest can help. Our team of licensed civil engineers can evaluate your site’s soil conditions and provide an effective solution regardless of what the investigation reveals. To get a FREE consultation and quote, contact us today.