Soil and footings
Footing and slab design, soil tests and site classification in Canberra
Your certifier needs footing and slab details with a nominated founding depth and a description of the founding material. We arrange the soil test, classify your site and design the footings and slab for it.
- From $1,290 + GST ($1,419 inc GST), soil test at cost
- Fixed quote in under 20 minutes on average, during business hours
- Founding depth and founding material, shown on the drawings for your certifier
Prefer to talk? Call 02 6189 9876
Or email info@canberrastructuralengineers.com.au
Monday to Friday, 8:00am to 5:00pm
- Engineering onlyWe never sell the repair or the build.
- Footings from $1,290 + GST($1,419 inc GST), soil test at cost.
- Fixed quote in under 20 minutes on averageDuring business hours, Monday to Friday.
- Canberra and the Queanbeyan sideEvery district, plus Queanbeyan, Jerrabomberra and Googong.
In short
Footing and slab design with site classification in Canberra starts from $1,290 + GST ($1,419 inc GST), with the soil test arranged at cost. Your certifier must lodge footing and slab details showing the founding depth and founding material, and an incomplete lodgement fails the completeness check. Canberra's ground can change within one block, so every site gets its own classification. Same prices across Canberra, Queanbeyan, Jerrabomberra and Googong.
- Fee
- From $1,290 + GST ($1,419 inc GST)
- Quote
- Fixed, in under 20 minutes on average, during business hours
- Soil test
- Arranged by us, passed on at cost
- You receive
- Site classification, plus footing and slab calculations and drawings
- Inspection
- Your certifier inspects the footings before the concrete is poured
- Area
- Every Canberra district, plus Queanbeyan, Jerrabomberra and Googong
Do I need a soil test or geotechnical report in the ACT?
No ACT law names a geotechnical report for a house. What your certifier needs is footing design for your site's soil, and a soil test is how we get there.
The Registrar's form AF2025-18, approved on 15 September 2025, lists the minimum documents a certifier must lodge for a house or class 10 building approval. For footings and slabs, that means:
- dimensioned footing and slab plans;
- the "nominated founding depth and description of founding material";
- reinforcement and cover, slab preparation and concrete strength.
If those details are on the engineer's plans, the certifier notes "Engineering Plans" on the checklist. An incomplete lodgement fails the completeness check. So the soil test isn't a legal box to tick: it's how we know what founding depth and material to put on the drawings. We arrange it and pass on its cost.
Builders, designers and certifiers can send plans directly; see engineering for builders, designers and certifiers.
What do the AS 2870 site classes mean?
A site classification sorts your block by how much its soil moves as it wets and dries. The class, from A to P, sets how stiff and deep the footings and slab need to be.
| Class | In plain words |
|---|---|
| A | Mostly sand or rock: little or no ground movement as moisture changes |
| S | Slightly reactive clay: slight ground movement |
| M | Moderately reactive clay or silt: moderate ground movement |
| H1 | Highly reactive clay: high ground movement |
| H2 | Very highly reactive clay: very high ground movement |
| E | Extremely reactive clay: extreme ground movement |
| P | Problem site, such as uncontrolled fill or soft ground: the footing needs specific design |
AS 2870 is the Australian Standard for residential slabs and footings. No official map gives a site class for any Canberra suburb.
Published geotechnical reports for individual new-estate blocks show how much a class can say. One block, with controlled fill, was "high range Class H1* (highly reactive/filled)", and the engineer advised "a footing system stiffer than the typical Class H1 detail". Another was H1* on its worst-case profile, but "part of the block would be equivalent to Class S conditions due to shallow rock".
Those are single blocks, not suburbs. Every site needs its own classification, and the same reports warn that uncontrolled fill means "Class P conditions" and that the class must be reassessed after cut or fill. Our guide to building on a new estate block covers fill in more detail.
Why does Canberra ground vary so much from block to block?
Because Canberra's rock is often deeply and unevenly weathered. Rock can be near the surface on one part of a block and metres down on another.
Geoscience Australia's notes on Canberra's engineering geology say deeply weathered zones "are common" where the Canberra Formation lies underneath: the inner north, most of Gungahlin, Kingston and Barton. Where hard rock sits near or at the surface, "the necessary blasting adds to excavation costs". Most Canberra suburbs are on the Williamsdale soil landscape, which ACT soil mapping flags for a "widespread foundation hazard". That's a warning about the landscape, not a site class for your block.
So a block in Gungahlin and a cut-and-fill block in the Molonglo Valley are each classified on their own soil. Our guide to Canberra soils and footings goes deeper into the geology.
When does the certifier inspect the footings?
Before the concrete is poured. The certifier inspects the footings after excavation, formwork and steel are in place; for a house, the structural frame is inspected again before it's lined.
That's when the founding depth and material on our drawings matter on site. The certifier and builder compare the excavation with the drawings before any concrete goes in.
If the ground found on the day doesn't match what the drawings describe, raise it before the pour, not after. Changing a footing in an open trench is far simpler than fixing one under a finished slab.
Next comes the slab level. The builder must not build above damp-proof course level until the certifier has a plan signed by a registered surveyor showing the building's position and floor levels.
What's included in footing and slab design?
A site classification from a soil test we arrange at cost, then footing and slab calculations and drawings your certifier and builder can use. Your fixed quote says if a site visit is needed.
It's the engineering under most new building work:
- new homes and knock-down rebuilds
- granny flats and dual occupancies
- extensions that need new footings
- garages and other class 10 buildings that need building approval
Every published price is on our prices page.
| Service | From |
|---|---|
| Footings, slab and site classification | $1,290 + GST ($1,419 inc GST) |
| Footings near a sewer or stormwater main | $790 + GST ($869 inc GST) |
| Retaining walls | $890 + GST ($979 inc GST) |
| Desktop review of an existing soil report or slab design | $390 + GST ($429 inc GST) |
What should I send for a footing quote?
We're engineers only. We don't dig, pour or recommend builders, so the design follows your soil and nothing else.
- Your plans, or the builder's slab layout if you have one
- The suburb and a photo of the block, showing any slope
- Any soil report or site classification you already have
- Anything you know about fill, trees or pipes on the block
What happens next?
Three steps, and you know the price before anything is booked.
Send your plans
Use the form above, or our full quote form. Add up to 5 photos or plans.
Get a fixed quote
In under 20 minutes on average, during business hours. It covers the design, and the soil test at cost.
Soil test and design
We arrange the soil test, classify the site and send footing and slab drawings for your certifier and builder.
Where footing design comes in
Every service is quoted at a fixed price before we start. Send photos or plans and we reply in under 20 minutes on average, during business hours.
Knock-down rebuild engineering
Site classification of the cleared block, footing and slab design, and structural drawings for the new house.
Fixed quotefrom your photos or plans See the service
Granny flats & dual occupancy
Slab, footing, frame and retaining engineering for a secondary residence or a second home on your block.
Fixed quotefrom your photos or plans See the service
Building on a new estate block in Canberra
What published site reports reveal about fill, reactive clay and shallow rock on new blocks, how slopes and boundary limits shape the design, and the protections that come with a new home.
Read the guideSoil test and footing questions
Something else on your mind? Call 02 6189 9876, email info@canberrastructuralengineers.com.au or send photos for a fixed quote.
How much does a soil test and site classification cost in Canberra?
Footing and slab design with site classification starts from $1,290 + GST ($1,419 inc GST). We arrange the soil test and pass its cost on with no mark-up.
What site class is my suburb?
There's no official map of site classes for Canberra suburbs. Neighbouring blocks can differ, so each block is classified from its own soil test.
Can I use the soil report from when my house was built?
Send it, and we'll tell you. A report from before later cut, fill or demolition may not describe the ground now. Published block reports say the class must be reassessed after cut or fill.
What is a founding depth?
It's how deep the footing goes to reach suitable ground. The drawings give that depth and describe the material the footing sits on, and the certifier checks the excavation before the pour.
Do you design footings and slabs for builders and designers?
Yes. We work from your plans and send footing and slab drawings your certifier can lodge, with the founding depth and material shown.