Complying development does not eliminate site-specific ground issues
A complying development certificate is an approval pathway, not a guarantee that every site has the same foundation or excavation conditions. A certifier, builder or structural engineer may request geotechnical information relevant to the proposed work, depending on the project and applicable requirements.
Some residential projects may need an AS 2870 site classification for footing design. Others may raise additional questions about retaining walls, sloping ground, excavation, fill or neighbouring structures.
Common CDC project examples
New dwellings, eligible additions and some secondary-dwelling projects can involve different geotechnical questions even where their approval pathway is similar. The information needed depends on the actual design, footprint, terrain and responsible certifier's request.
- Site classification for a proposed residential footing or slab system.
- Ground information for a granny flat or extension in a constrained rear yard.
- Targeted assessment of proposed retaining walls or changes to levels.
- Additional advice where slope, fill or excavation affects the project.
- Construction-stage inspection if specified by the relevant design documents.
Use the certifier's exact wording
The safest starting point is the written request or checklist from the certifier, builder or design team. Forward the original wording together with architectural drawings, survey information, the site address and relevant structural details.
This helps distinguish a site classification request from a broader geotechnical investigation or a separate slope assessment. It also avoids an unsupported claim that all CDC projects require identical reports.
Pricing depends on the required scope
Sydney Geotechnical's residential site classification starts from $750 where that service matches the actual request. Broader investigations start from $2,200, while DA and CDC-specific support is scope-based.
The final quote should reflect the proposed development, access, site conditions and engineering deliverables rather than the name of the approval pathway alone.
Common questions
CDC geotechnical requirements: common questions
Does every complying development certificate require a geotechnical report?+
No. Requirements depend on the proposed development, site conditions, applicable provisions and the certifier or project professional's specific request.
Is a CDC site classification the same as DA support?+
Not necessarily. A site classification supports residential footing design, while DA or CDC support may involve other specific geotechnical questions identified by the project team.
What should I upload for a CDC geotechnical quote?+
Send the site address, architectural plans, available survey, certifier or builder request, proposed excavation or retaining details, and access photographs where relevant.
Need CDC geotechnical support in Sydney?
Get a scope matched to the project
Send the site address, proposed works, current plans and any request from your builder, engineer, council or certifier. Sydney Geotechnical will review the information and confirm an appropriate scope and fee.
This guide provides general information only and is not a substitute for investigation, engineering advice, footing design or approval advice for a particular property. Project requirements and ground conditions must be assessed site by site.
