How much does a geotechnical investigation cost in Sydney?

Every investigation is a fixed fee, confirmed in writing within one business day of receiving the address. There is no published starting figure. The fee is set against the number and depth of boreholes, rig access and the laboratory programme the design calls for, and the Principal reviews the block and plans before quoting. What moves a quote is on the geotechnical report cost guide.

How deep are the boreholes?

Residential boreholes are sized to the base of the proposed excavation plus one to two metres, so a basement or deep piers call for deeper holes than a slab on grade. Target depths are set from your plans at the desktop review. The 4WD-mounted rig drills where it can reach and motorised hand augers cover the rest; the engineer checks every log.

Do I need a geotechnical investigation for a DA or a CDC?

It depends on the pathway and the block. For a DA, the council can require one, in its DCP or after lodgement. For a CDC, the certifier who issues it asks. A standard house or pool on a level block typically needs only an AS 2870 site classification. Basements, boundary excavation, retaining walls, sloping or landslip-mapped land, fill or a Class P result usually trigger a full investigation.

Geotechnical Investigations · Principal-Led · Sydney

Geotechnical Investigations. Engineered Properly.

Boreholes, penetrometers and NATA-backed laboratory data, turned into reports your certifier, council and structural engineer can act on, for DAs, complying development, footings, basements and retaining structures across Sydney. The engineer who stands on your ground is the engineer who signs your report.

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Boreholes to AS 1726, quoted per site · Fixed fee in writing within one business day · Reports with laboratory testing typically 8 to 12 business days from fieldwork

Free site visit · Same-day site visits across Metro Sydney

5.0 from 33 Google reviews

01 · Scope

What The Investigation Covers.

DA & CDC Reports

Geotechnical reports written to answer the questions your council, certifier or structural engineer will actually ask, prepared with the approval pathway in mind from the first borehole.

Footing & Slab Design Input

Investigation depths, bearing parameters and founding recommendations your structural engineer can design from directly, without a second round of questions.

Basements, Excavations & Retaining

Subsurface profiles, groundwater observations and lateral parameters for basements, cut batters and retaining structures on Sydney’s stepped and sloping blocks.

Drilling, DCP & Lab Testing

Borehole drilling with our 4WD-mounted rig and motorised hand augers for tight access, dynamic cone penetrometer testing, and NATA-accredited laboratory testing where the design calls for it.

02 · Fieldwork

Led By The Engineer.

No drive-by inspections. The Principal Engineer leads the drilling, reads the profile as it comes out of the ground, and cross-checks it with in-situ testing on the spot, so by the time the report is written, the ground has already been read twice.

SFGEO engineers working the rig at a borehole during night works on a Sydney street

Fieldwork

Soil sample opened beside the field board at BH01, 0.50 to 0.95 m

Logged On Site

03 · Sydney Ground

The Ground Changes By Suburb.

Sydney sits on a handful of very different geologies, and the investigation is scoped to the one under your block, not a city-wide average. Two doors down from a stable site, your land can behave completely differently.

Four runs of rock core in a tray at BH2, coring from 4.1 metres, laid out and labelled for logging

Rock Core · BH2 From 4.1 m

Inner West

Ashfield Shale country: residual clays over weathered shale, often moderately to highly reactive. Investigations here focus on clay depth and shale weathering, because the difference decides the footing system. Class M and H1 outcomes are common.

North Shore

Hawkesbury Sandstone, with outcomes hinging on how much weathered soil sits above the rock. Shallow rock founds beautifully. Bored piers to sandstone carry most of the harbour’s basements. Deeper profiles behave like clay and need proper investigation.

Western Sydney

Bringelly Shale, the most reactive common profile in metropolitan Sydney. Across the Cumberland Plain, H1 and H2 outcomes are frequent, and movement estimates need boreholes deep enough to see the whole active zone.

South West Corridor

Legacy fill, alluvial soils and reactive clays. Uncontrolled fill left under the footings or slab can make a site Class P under AS 2870. Where the fill is stripped, the class is set by the natural ground beneath. The investigation’s first job is finding where the fill stops and natural ground begins.

Eastern Suburbs & Coast

Dune sands over sandstone, steep marine slopes and tight streets. Sand profiles found well but cave in open excavations; the rock surface dips sharply block to block. Investigations here earn their keep on access and depth-to-rock.

Not sure which one you’re on? Send the address. The desktop geology is checked before we even quote.

Check My Block

04 · Why Early

Ground Found Late Costs The Most.

Unexpected rock, fill, or reactive clay discovered after contracts are signed becomes a variation, priced by whoever has the upper hand at that moment. An investigation done properly, and done early, converts those unknowns into design parameters while every option is still open and competitively priced.

Turnaround is scoped at first contact, and urgent DA, CC and settlement timelines can be accommodated. Call the Principal directly to arrange priority scheduling. And where standard rigs stop at the kerb, our 4WD rig and motorised hand augers keep going. See tight-access drilling.

Investigations are quoted fixed-fee against the number and depth of boreholes, access and the laboratory programme. Most fall under our Complex Projects tier (basements, multi-storey, retaining walls, sloping or restricted-access blocks), and the fee is confirmed in writing within one business day. What moves the figure is set out in the geotechnical report cost guide.

Client Feedback.

5.0 on Google · 33 reviews

“I had a great experience with Ali and his team for the geotechnical investigation at my property. The team was very professional, thorough and easy to communicate with. They carried out the manual soil investigation and DCP testing carefully on site, and took the time to explain the soil conditions and results clearly. I really appreciated their practical approach and attention to detail. Ali was also very helpful in explaining the findings and how they could affect the proposed foundation design. Highly recommended Ali and his team for anyone looking for a professional and reliable geotechnical service.”

deng Eric

“I can’t recommend Alli & Solid Foundation Geotechnical highly enough. After our structural engineer made a last minute change to the plans, I contacted Alli at 5 pm the night before and he went above and beyond by rearranging his schedule to attend our site the next morning. His responsiveness and willingness to help at such short notice were truly appreciated. He understood the urgency of the situation and acted quickly to help keep our project moving. We are extremely grateful for his prompt service and would not hesitate to use again or recommend Alli & Solid Foundation Geotechnical to anyone. All the best, Blueshore Projects”

Jake Rutherford

“We engaged Alli for cfa drilling on a major civil project and couldn't be happier with their work. The team arrived on time, communicated clearly about timelines and site logistics, and delivered high-quality samples with excellent documentation. They handled our site conditions professionally and were responsive to any adjustments we needed. The data they provided was accurate and instrumental to our project design phase. Would definitely recommend them for any geotechnical drilling needs.”

Jonathan Tat

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Common Questions

An AS 1726 geotechnical investigation provides the ground data for Sydney DAs, CDCs, footings, basements and retaining structures. Boreholes, penetrometers and NATA-accredited laboratory data become a report your certifier, council and structural engineer can act on. Fees are fixed and quoted per site. Reports with laboratory testing typically take 8 to 12 business days from fieldwork, confirmed in the written quote, with interim findings available where the programme needs them. The engineer who stands on your ground signs your report.

Typically 8 to 12 business days from fieldwork when NATA-accredited laboratory testing is included, with interim findings available where the programme needs them. The turnaround is confirmed in the written quote. The laboratory schedule is the main variable, and testing is added only when the site warrants it. Urgent DA, CDC and construction deadlines are taken on regularly. Send the date with the address and you will have a yes or no before any fee is agreed.

The report sets out the subsurface profile, layer by layer, with groundwater observations. Each borehole is logged, engineer-checked and plotted on a plan. Penetrometer and laboratory results, where tested, sit behind the allowable bearing pressures and founding recommendations for the footing types on your plans. Lateral parameters cover basements, cut batters and retaining structures. It is written to your certifier’s requirements and signed by the engineer who led the fieldwork.

Start With The Ground.

Every SFGEO engagement begins with the Principal Engineer reading your block and your plans, and standing on your ground on the day. Detailed answers to common questions are on the full FAQ.

Call 0423 483 555 Request A Quote