Is a soils report the same thing as a geotechnical report?

Yes — same document. "Soils report" is the common name. "Geotechnical investigation report" is the formal engineering term. You'll hear both used interchangeably.

Do I need a soils report for my ADU?

In most jurisdictions, yes — especially for detached ADUs with new foundations. Some cities waive the requirement for attached ADUs on flat lots with an existing report on file. We can check the specific requirements for your project.

Can I use an old soils report for a new project?

Sometimes. If a previous report covers the same site and the scope is compatible, some jurisdictions will accept it with an update letter. But if the project has changed significantly — different foundation type, different building location — a new investigation is usually required.

What happens if my soil is "bad"?

There's no such thing as bad soil — just soil that requires specific engineering. Expansive clay, loose fill, high groundwater, liquefiable sand — all manageable with the right foundation design. That's the entire point of the investigation: identify conditions and engineer around them.

Who else uses my soils report?

Your structural engineer uses it for foundation design. Your civil engineer uses it for grading and drainage. Your contractor uses it for earthwork. The building department uses it for plan check. It's the document that connects every discipline on your project.

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What Is a Soils Report?

The foundation of your foundation — why this is the first thing any serious project needs, and what you're actually paying for.

Your Building Is Only as Good as the Ground Beneath It

Here's something most people don't think about until a plan checker tells them: the dirt under your project isn't just dirt. It's a complex system of soil layers, groundwater, seismic conditions, and load-bearing characteristics that will directly determine whether your foundation lasts 100 years or starts cracking in 5.

A soils report — formally called a geotechnical investigation report — is the engineering study that figures all of this out before you pour a single yard of concrete. A geotechnical engineer drills into your site, pulls soil samples, runs laboratory tests, and writes a set of recommendations that your structural engineer and architect use to design a foundation that actually works for your specific site.

Think of it this way: your architect designs what your building looks like. Your structural engineer designs how it stands up. Your geotechnical engineer tells both of them what they're standing on — and that information changes everything.

What's Actually in a Soils Report

Not all soils reports are the same, but a good one answers the critical questions your entire project team needs:

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Subsurface Exploration

We drill borings into your site to see what's actually down there — soil types, rock layers, fill material, groundwater depth. No guessing, no assumptions. This is the field work that makes everything else possible.

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Laboratory Testing

Your soil samples get tested for shear strength, compressibility, moisture content, and expansion potential. These aren't academic numbers — they directly determine your foundation type, size, and reinforcement.

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Foundation Recommendations

Bearing capacity, footing depths, slab thickness, reinforcement requirements, settlement estimates. This is what your structural engineer needs to design a foundation that won't move, crack, or settle unevenly.

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Seismic Hazard Assessment

Liquefaction potential, seismic settlement, lateral spreading risk, and site-specific ground motion parameters. In California, this isn't optional — CBC and ASCE 7 require it. Your report tells your structural engineer exactly what seismic forces to design for.

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Earthwork & Grading Guidance

How to prepare your site — cut and fill specs, compaction requirements, subdrain recommendations, slope stability guidance. Your civil engineer and contractor use this to build the site correctly before the foundation goes in.

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Groundwater & Drainage

Depth to groundwater, percolation characteristics, and drainage recommendations. This affects everything from foundation waterproofing to your stormwater BMP design to whether you can use seepage pits.

Need Soils Reports & Geotechnical Investigation? We serve all of Southern California.

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Why This Isn't Just a Permit Checkbox

Yes, every jurisdiction in California requires a soils report for new construction. But that's not why you should care about getting a good one.

A soils report prevents expensive surprises. It tells you if you're building on expansive clay that will heave your slab, on loose fill that needs to be recompacted, on shallow groundwater that requires waterproofing, or on a slope that needs deeper footings and tiebacks. Finding out during construction means change orders, delays, and arguments with your contractor about who's responsible. Finding out during design means you engineer around it from day one.

This is the document that connects every discipline on your project. Your structural engineer can't design the foundation without it. Your civil engineer can't finalize the grading plan without it. Your contractor can't bid earthwork accurately without it. And the building department won't approve your plans without it.

We've seen projects where a developer tried to save a few thousand dollars by skipping the soils report or reusing an old one from a different site. Every single time, they ended up spending 10x more fixing problems during construction that a proper report would have caught.

When You Need a Soils Report?

Common project types and triggers:

New Home

Required by every jurisdiction. Your structural engineer can't design the foundation without it.

ADU / Guest House

Most jurisdictions require it for detached ADUs with new foundations. Some waive for attached ADUs on flat sites.

Addition or Remodel

Required when adding new foundation elements — especially if the original building never had a geotech report.

Retaining Walls

Walls over 3–4 feet typically require geotechnical design parameters — lateral earth pressure, bearing capacity, drainage.

Hillside Development

Always required. Slope stability, setback recommendations, and specialized foundation design are non-negotiable on slopes.

Swimming Pools

Required in many jurisdictions, especially on slopes or in areas with expansive soils or shallow groundwater.

Commercial Projects

Always required. Higher loads mean deeper borings, more lab testing, and more detailed analysis.

Grading Permits

If you're moving significant earth, the building department requires geotechnical oversight of the grading operation.

Common Questions

What clients typically ask about a soils report?:

Ready to Move Forward?

We handle a soils report? for projects across Southern California.

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