In most cases, yes. Councils often require a geotechnical report for new buildings, significant extensions, subdivisions and retaining walls, particularly where the site has slopes, soft soils, liquefaction risk groundwater issues or other natural hazards. 

Getting geotechnical advice early can identify ground constraints before they become design changes, consent delays or construction problems. For some projects, a site suitability assessment is the first step to work out whether a full geotechnical investigation is needed. 

If you are unsure where to start, send us your site details and proposed development using the enquiry form. We can advise what level of geotechnical input is likely to be required. 

Sometimes. If the report is recent, relevant and covers the same part of the site you intend to develop, it may still be useful. 

However, if the design has changed, the site has been altered, the proposed development is different, or council requirements have shifted, the report may need to be reviewed or updated. Most geotechnical reports also include limitations that explain what the report can and cannot be used for. 

If in doubt, it is best to check before relying on it. Send us what you have and we can advise whether the existing report is likely to be suitable for your intended purpose. 

For residential sites, a geotechnical report typically takes around 2 to 4 weeks, depending on the scope of investigation, site access, fieldwork availability and whether laboratory testing is required. 

Larger or more complex projects can take longer, especially where drilling, geophysics, specialist testing, natural hazard assessment or staged investigation is needed. 

Once we understand your project and site, we will give you a realistic programme before work begins. 

Cost depends on the type of project, the complexity of the site and the level of investigation required. Simpler sites with lower geotechnical risk cost less; complex or hazard-prone sites need more investigation, and will cost more.  

The main factors influencing cost are: 

• the type and scale of development (e.g. residential, subdivision, commercial) 

• the known or likely ground risks (e.g. slopes, soft soils, liquefaction, expansive soils or highly variable ground) 

• the number and type of investigation points required 

• whether laboratory testing, geophysics or specialist analysis is needed 

• local council and consent requirements 
  

Our approach is to match the level of investigation to the project and the risk. We can carry out an initial desktop review and site walkover to outline the likely scope and fees before more work begins. 

In most cases, yes. Challenging ground conditions do not automatically mean a site cannot be developed, but they can affect the foundation type, earthworks, retaining requirements, drainage strategy, construction method and overall project cost. 

Typical responses may include: 

• Liquefaction or soft soils: raft foundations, ground improvement, engineered fill or deep foundations, depending on the site and structure. 

• Slopes or instability: setbacks, drainage control, retaining structures, anchors or slope stabilisation measures. 

• High groundwater or poor soakage: adjusted stormwater design, subsoil drainage, waterproofing measures or alternative disposal methods. 

The right solution depends on the ground conditions, the proposed development and the level of risk. We work closely with structural and civil designers, so the design is safe, compliant and proportionate, not over-engineered for the conditions. 

On straightforward sites, the minimum investigation may be enough. On more complex or hazard-prone sites, extra investigation can reduce uncertainty and lead to better decisions. The minimum may get a project through consent, but it can leave gaps that need to be covered through conservative design, larger contingencies or changes during construction, which can substantially increase costs.  

Additional investigation can help: 

• provide better design parameters for foundations, retaining walls and earthworks 

• reduce unnecessary conservatism where the ground conditions are better understood 

• identify construction risks before work starts on site 

• support a smoother consent process 

• improve long-term performance by better understanding settlement, slope movement, groundwater or stormwater risks 

In short more investigation is not always needed, but on complex sites, more data upfront usually means less risk, better decisions made earlier, lower cost and fewer problems later in the project.