How it works, start to finish.
The process for a geotechnical investigation in Christchurch and Canterbury, the deliverables it produces, and the questions builders ask before they start.
The same discipline, ground or structure.
Whether the job is a geotechnical report or a structural design, the shape is the same. Investigate first, design to what the investigation found, and sign only what the evidence supports. The steps below are how that runs on a real project.
From enquiry to producer statement.
The path a project takes through the practice.
- 01
Enquiry and site visit
You send the plans, we look at the ground. Testing commences within two to three weeks of confirmation.
- 02
Investigation
Shallow ground tested to 3.0m, then deep testing where the loads need it. Every layer logged.
- 03
The report
Findings, site classification, and founding recommendations, issued two to three weeks after testing. Four weeks total for super-urgent jobs.
- 04
Design
The foundation or structure designed to what the ground allows. The design package follows within four weeks of confirmation.
- 05
Producer statement
Where the design supports it, signed and issued, with construction monitoring where required.
What the investigation logs.
An investigation reads the ground top-down, the way a bore log reads, from the topsoil to the layer that will carry the load. The depths below are indicative, not a specific site.
What your report contains.
The document the council officer reads, and the structural design builds on.
Ground conditions and soil profile
Each layer described and measured against the depth it was found at, with the changes in strength recorded as the hole goes down.
Site classification
The technical category and any liquefaction hazard, set from the testing.
TC1 to TC3 explainedFounding recommendations
What the ground will carry, and the foundation type it supports.
Test results
The shallow and deep testing, recorded so another engineer could check it.
Further testing, where needed
A recommendation for slope stability modelling or deeper work where the ground calls for it.
Bearing and settlement figures
The numbers the structural design is built on: what the founding layer will carry, and how much movement to expect under load.
The terms, explained.
The language on a consent, in plain English.
Producer statements (PS1, PS2, PS4)
PS1 is the design sign-off, PS2 is a review of a design, and PS4 is the construction review a council asks for as part of the code compliance application. Registered Producer Statements Author, Auckland Council: PS1, PS2, PS4.
TC1, TC2, TC3
The technical categories that classify Canterbury land for foundation design. TC3 ground needs the most detailed investigation.
TC1 to TC3 explainedLiquefaction
Ground that can behave like a liquid in a large earthquake. Sites prone to it require detailed investigation.
Percent NBS
A building rated as a percentage of the new building standard. Below 34%NBS it is an Earthquake Prone Building.
What %NBS meansDesign Features Report
The DFR, part of a structural design package, alongside the calculations and drawings.
Questions builders ask.
The straight answers, before you start.
Do I actually need a geotechnical report?
For most building and resource consents, yes. Councils require the ground to be investigated, not assumed.
Can I skip it to save time?
The council can ask for one anyway, and the build stops while you get it. It is the cheapest part of the job to do, and the most expensive to redo.
How long does it take?
Testing commences within two to three weeks, and the report is issued two to three weeks after. Super-urgent jobs can run to four weeks total.
Why use one firm for both?
The gap between a geotechnical engineer and a structural one is where consent risk lives. Here there is no gap, because it is one practice.
Is my site TC3 or liquefaction prone?
That is what the investigation confirms. We test the ground and classify it, rather than guess from the street.
TC1 to TC3 explained
We will tell you straight.
If your site is simple, we will say so. If it needs deeper work, we will tell you why, and show you the ground that says it. Builders keep coming back because the answer holds up when the council reads it.
Geotechnical ReportsStart with the ground.
If a question here did not cover it, send the plans and ask. The answer comes back from the engineer who would do the work, not from a form.