Do I Need a Soil Test Before Building a Pool?

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Not always required, but it is what makes a quote comparable. A soil test classifies the site under AS 2870 — classes A, S, M, H1, H2, E and P — which drives the concrete shell and footing design and the rock allowance. Excavation and access cost $8,000 to $35,000, and the rock clause is where that price is won or lost.

The short answer

The site class is determined per block by a test, never per suburb or postcode. No builder can tell you your class from an address.
AS 2870 runs A, S, M, H1, H2, E and P — stable sand through extremely reactive clay, and P for problem sites.
The test is what makes the rock allowance in a concrete pool contract a real price rather than an estimate — and what makes two quotes comparable.
Excavation and site access are $8,000 to $35,000 nationally — the widest single range in a pool quote, and wider than the barrier, paving and landscaping combined.
A builder who cannot state a definite amount may carry rock as a provisional sum. That is legitimate; an unexplained one is not.

AS 2870 site classes, and what each one signals for a pool excavation
Class	Ground	What it tends to mean for a pool
A	Sand or rock, little or no movement with moisture	Predictable excavation; rock, if present, is the variable
S	Slightly reactive	Generally straightforward
M	Moderately reactive clay or silt	Common across much of Australia; design accounts for movement
H1	Highly reactive	More movement; shell and surround design matter more
H2	Highly reactive, greater movement	As above, with tighter engineering
E	Extremely reactive	Highest movement class; expect engineered detailing
P	Problem site — fill, soft soil, abnormal moisture	The class that changes the quote most; needs specific engineering

What the test is actually for

A geotechnical site investigation bores the ground and classifies it under AS 2870, the Australian Standard for residential slabs and footings. The classes run from A — sand or rock with little movement as moisture changes — through S, M, H1, H2 and E for increasingly reactive clay, to P for a problem site with fill, soft soil or abnormal moisture conditions.

For a house that classification drives the footing design. For a pool it does two jobs: it informs the shell and surround engineering, and it tells everyone what is actually down there before a machine arrives. The second job is the one that saves money.

The rock clause, and why the test pays for itself

Look at the excavation line in any concrete pool quote and you will usually find rock treated as a provisional sum or an hourly rate. That is legitimate: the QBCC defines a provisional sum as an estimate used where the contractor cannot state a definite amount after making all reasonable enquiries, and gives rock removal as the example.

A soil report is one of the reasonable enquiries. With one, the allowance is grounded in what the boreholes found. Without one, two builders can quote the same pool $15,000 apart purely by choosing different rock allowances, and the cheaper quote is not the cheaper pool — it is the one that reconciles upward later.

So the useful question is not "do I need a soil test" but "what is your rock allowance based on". What a provisional sum is covers the mechanics, and why a pool costs more than the contract covers what happens when nobody asked.

The honest limit: your neighbour's report is not your report

Site class is determined per block. Two houses on the same street can classify differently, and within a single block the ground can change between the front and the back. This is why nobody — not a builder, not a council, not this page — can tell you your site class from your suburb.

Be sceptical of any quote that assumes a class, and of any advice that a whole area is "all sand" or "all rock". Regional generalisations are useful for expecting a surprise, not for pricing one.

Where the ground carries a mapped regulatory constraint rather than an engineering one — acid sulfate soils on the New South Wales coast, for instance — that is mapped, and it appears on the planning certificate. See acid sulfate soils and pool excavation.

When to get one, and who arranges it

Get one before you sign if the block slopes, if there is any history of fill, if neighbours have had rock, if the pool is going close to the house or a boundary, or if the quotes you are holding differ sharply on excavation. Those are the cases where the report changes the number.

Often the builder arranges it and passes on the cost; sometimes an engineer is engaged directly. Either way, ask for the report itself rather than a summary, and give the same report to every builder you are comparing — which is the point, because quotes are only comparable when the inputs are. You can get quotes on that basis.

Common questions

What is AS 2870?

AS 2870 is the Australian Standard for residential slabs and footings, which classifies a site by how much the ground moves with moisture — classes A, S, M, H1, H2, E and P. It is the framework Australian engineers use for site classification; see this summary of AS 2870-2011 for an accessible explanation. The standard itself is the authority.

Does a soil test guarantee I will not hit rock?

No. Boreholes sample points, not the whole excavation, and rock can sit between them. What the report does is move the rock allowance from guesswork to evidence, and give you grounds to question an allowance that does not match it.

Can I use the soil report from when the house was built?

Sometimes, as background. But it was taken for the house footprint, and your pool is going somewhere else on the block — often the part that was filled or levelled when the house was built, which is exactly the condition that produces a P classification.

Who pays for the soil test?

Usually the owner, whether directly or through the builder. It is a small cost against an excavation line of $8,000 to $35,000, and it is the cheapest way to make competing quotes actually comparable.

Sources

General information only, current at 2026-09-10. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.

Do I need a soil test before building a pool?