The report behind every safe foundation
At California Soil Testing Inc., we specialize in soil reports for residential projects, done accurately and fast.
Who we are
Our focus is soil reports for residential projects: the geotechnical investigations and recommendations behind the homes, ADUs, additions, decks, and pools that developers, families, and businesses across Northern California build every day. Based in San Jose, we combine field exploration with our own laboratory analysis to deliver reports that answer the questions these projects raise.
We're a local firm, and it shows in how we work: same-day quotes, phones answered by the people doing the engineering, and a friendly, straightforward approach to a technical trade. Every report we issue is signed and stamped by a licensed Professional Engineer and built to pass plan check the first time.
Our in-house laboratory, operating in compliance with AASHTO and ASTM standards, means your samples never wait in a third-party queue. That's how we back a 3-week project turnaround guarantee.
At a glance
- Reports signed & stamped by a licensed Professional Engineer (PE)
- In-house laboratory, AASHTO & ASTM compliant
- 3-week project turnaround guarantee
- 24-hour quote & proposal response
- 100% building-department compliance record
- OSHA-certified shoring for drilling operations
- Serving the Bay Area, Monterey County, Santa Cruz, Sacramento & beyond
Accuracy first
Foundations are only as good as the data beneath them. We log, sample, and test with the rigor your structural engineer depends on.
Speed without shortcuts
In-house lab work and same-day proposals keep your permit timeline moving without compromising the engineering.
People you can call
Immediate telephone consultation is part of the service. Questions during construction? You'll reach an engineer, not a queue.
What our clients say
You guys are the best. I called you one day and needed something done quickly. Geo report the next day, which was Saturday. You were out and completed two borings at the old San Joaquin General Hospital building that we're converting into a medical training university. Five stars, ten if I could give it. Excellent price and timing. Thank you!
I'm a GC, and when I need a soil test or anything involving a geotechnical report, I call them.
Thank you! You guys did a great job!
They were very helpful.
Great service. The prices are reasonable and friendly customer service. I highly recommend it.
We needed some recommendations for our foundation and they did a great job helping us. Highly recommend!
Frequently asked questions
The questions homeowners, builders, and architects ask us most.
What is a soil report, and why do I need one?
A soil report (geotechnical investigation report) describes the soil and groundwater conditions on your property and tells your structural engineer how to design a foundation for those conditions: bearing capacity, foundation type, seismic parameters, drainage, and grading criteria.
Most building departments in Northern California require one before they'll issue a permit for new construction, additions, ADUs, and hillside work. It's also simply how you avoid expensive surprises: cracked slabs, settling foundations, and failed retaining walls usually trace back to soil conditions nobody checked.
Do I need a soil report for an ADU?
In most Northern California jurisdictions, yes. A detached ADU is new construction and typically requires a geotechnical report for permit approval. Requirements vary by city and by site conditions, so send us your address and we'll confirm what your building department requires before you spend anything.
How much does a soil report cost?
It depends on the project size, site access, the number of borings required, and your jurisdiction's requirements. A simple ADU or addition costs considerably less than a hillside custom home in a seismic hazard zone.
We provide fixed-price quotes, usually the same day you ask, so there are no surprises. Request a free quote and you'll have a number within 24 hours.
How long does the process take?
We guarantee a 3-week project turnaround from field work to your finished, PE-stamped report. Quotes and proposals go out within 24 hours, usually the same day. If your permit timeline is tight, call us and we'll tell you honestly what's possible.
What happens during the site investigation?
Our crew visits your property and drills borings or excavates test pits, typically a few hours of work for a residential lot. We log the soil profile layer by layer, note any groundwater, and collect samples. The samples then go to our in-house laboratory for testing per ASTM and AASHTO standards. You don't need to do anything to prepare beyond providing access to the site.
What is a liquefaction study, and do I need one?
During an earthquake, loose, water-saturated soil can temporarily lose its strength and behave like a liquid. That's liquefaction,, and it can cause structures to settle or tilt. The State of California maps Seismic Hazard Zones where this risk exists, and if your property falls inside one, your building department will require a site-specific liquefaction evaluation before issuing a permit. We can check your parcel against the hazard maps when you request a quote.
What is a percolation test?
A percolation (perc) test measures how quickly water drains through your soil: specifically, the time it takes for the water level in a test hole to drop one inch. County health departments require perc results before approving a septic system or leach field, and the data also informs stormwater and drainage design.
What is compaction testing, and when is it required?
Whenever soil is placed as fill (under a building pad, behind a retaining wall, in a utility trench) it has to be compacted to the density specified in the grading plan, or it will settle later. We test the fill in the field as it's placed and issue a final compaction report the building department uses to sign off your grading.
Will my report be accepted by my building department?
Yes. Every report is signed and stamped by a licensed Professional Engineer and formatted to the requirements of your specific jurisdiction. We maintain a 100% building-compliance record, and if a plan checker has questions, we respond directly. That follow-through is included.
What if my design changes after the report is issued?
It happens all the time: an addition grows, a footing foundation becomes piers, or the footprint shifts on the lot. We update and re-issue reports to match the new design, and because we already know your soil, revisions are fast. Just send us the updated plans.
Do you stay involved after the report is delivered?
If you want us to, absolutely. We offer foundation plan review, foundation inspection, pier-drilling observation, drainage and grading inspection, crushed-rock inspection, construction meetings, and final inspection letters, plus immediate telephone consultation whenever questions come up during construction.
Have a question we didn't answer?
Call us. Immediate telephone consultation is part of how we work.