How to Read a Geotechnical Report Without Falling Asleep
A Practical Guide to Finding What Actually Matters in a Geotechnical Report
By Nathan McNallie/MCS Geotechnical Engineering
Introduction
Most people open a geotechnical report with good intentions…
and close it about three minutes later.
It’s not surprising. Geotechnical reports are dense, technical, and not exactly written for casual reading. But buried in those pages are decisions that directly affect cost, schedule, and constructability.
The goal isn’t to read every line. It’s to know where to look and what actually matters.
Start With the Boring Logs (They’re Not Actually Boring)
Yes, they’re called boring logs. No, they’re not the part you should skip.
These logs show:
Soil types at different depths
Groundwater observations
Where conditions change
This is the closest thing you have to “ground truth” for the site.
If you ignore this section, everything else becomes harder to interpret. The recommendations only make sense when you understand what was actually encountered.
Go Straight to the Recommendations
If you only read one section, make it this one.
This is where the report tells you:
Foundation types
Bearing values
Undercut or stabilization requirements
Earthwork guidance
This is also where projects quietly get expensive.
A line like:
“Undercut 2–3 feet below subgrade”
might look straightforward, but across an entire site, that can turn into a significant cost driver.
Don’t Skip the Assumptions
This is the part most people say they read.
Reports are based on:
Limited borings
Interpreted conditions between those borings
Assumed groundwater levels
In other words:
👉 It’s not a perfect map of the site—it’s a best interpretation of it.
When field conditions don’t match expectations, this is usually why.
Pay Attention to What’s Not Certain
Geotechnical reports rarely say something is guaranteed. They usually say:
“Based on available data…”
“It is anticipated…”
“Additional evaluation may be required…”
Those phrases matter.
They indicate where variability exists—and where decisions may need to be adjusted during construction.
Understand That Soil Isn’t Consistent
One of the biggest mistakes is assuming the entire site behaves the same way.
It doesn’t.
Conditions can change:
Between borings
Across short distances
With moisture and weather
Applying one recommendation uniformly across a site can lead to unnecessary work—or missed issues.
Use the Report as a Guide, Not a Script
A geotechnical report is not meant to be followed blindly.
It’s a starting point:
For planning
For estimating
For anticipating conditions
But real decisions happen in the field, where conditions are verified and adjusted.
The best outcomes come from combining:
The report
Field observations
Practical judgment
Conclusion
Geotechnical reports aren’t meant to be easy reading—but they are meant to be useful.
You don’t need to understand every technical detail. You just need to know where the important information is and how it affects the project.
Most of the time, the difference between a smooth job and an expensive one comes down to how those recommendations are interpreted—not just what’s written.
About the Author
Nathan McNallie is a senior geotechnical consultant with experience in construction materials testing, report review, and construction advisory services. He focuses on practical interpretation of geotechnical data to improve constructability and reduce project cost and risk.
