Why a soil test? - Owner Builder Club

Why a soil test?

Soil testing

Hello Owner Builders!

Well, what a pleasure it was to catch up with Tracey Dunn from Soil Test Express in Victoria. Tracey has kindly shared her expertise on the ins and outs of soil testing.

By the end of this Q&A, you'll discover the many why's behind getting a soil test.


In what instances does a soil test need to be carried out?

There’s quite a list of scenarios requiring soil testing for example building sheds, fences, retaining walls, pool, granny flats, garages and even stables.

Basically anything that’s going to have a footing will need a soil test.

Council will usually tell you that you need a soil test as part of the planning permit but it’s not always the case.

However, both Council and a Structural Engineer require soil test reports. Engineering can’t be done without a report, as an engineer needs to know how deep footings can go based on the soil profile.

A soil tester and Engineer are two people involved early on in the build.

Who co-ordinates the soil test?

Owner builder’s can organise soil testing directly with a soil tester or a Structural Engineer, Draftsperson/Building Designer/Architect can organise it on their behalf.

How can an Owner Builder best prepare for the 1st call to a soil tester?

We need a good idea of what and where an owner builder is planning to build. We always say plans would be helpful but it doesn’t always happen this way.

If it’s a vacant block, and there are no plans, what we usually do is scatter 3 ball holes across the block to get a soil profile and most Engineers/Draftspersons are happy with that.

How much can the quality of soil hinder or limit a build?

There are a few different scenarios that could potentially stop a build or really slow it down and get costly involving trees, water, rock and drainage.

1. Trees
There are Council regulations to consider. Depending on the Council you deal with, some Council’s for example, won’t let you remove trees so you can’t build a house because of trees.

If there are trees on the block that you can keep, you can put a root barrier around them or your footings would just need to go deeper so the tree roots won’t affect footings.

2. Water tables
There can be water tables if you live close to the beach or water that may require footings to go deeper to get past the water table.

3. Rock
It comes down to the type of rock. Basalt rock for example is one of the strongest rocks but can be costly if excavation is required.

You can also get what you call floaters, big rocks throughout the ground. When a soil test is done, it can be hit and miss because floaters are scattered in pockets throughout the site.

4. Drainage
Drainage can be another problem.

For example, clay (although it’s good to build on) and water do not like each other. There are 3 types of clay – M class (moderately reactive to water), H1 (highly reactive) and H2 (extremely reactive).

M class – movement is between 20mm to 40mm.
H1 – movement is between 40mm to 60mm
H2 – movement is between 70mm to 100mm+

There are ways around everything but it can get costly.

TOP TIP: If buying a block of land, undertake due diligence so you’re aware of potential issues.

ANOTHER TIP: If someone comes out to do a soil test and you’ve got fill on your site, technically you should not put footings in that fill because it’s loose and possibly not compacted. Be aware of this!

Is Soil Testing a regulated industry?

Soil testers need to have Professional Indemnity Insurance which is expensive. To get Owner builder insurance, you have to meet a certain criteria. For example, you have to have a qualified Engineer and that Engineer needs to provide proof of qualifications.

Should owner builders check if a soil testing service has the required insurance?

Yes! If a soil tester does not have the required insurance and something goes wrong down the track, the homeowner is up for the costs to rectify the damage.

Key points:

1. Your house insurance won’t cover the damage down the track.
2. Soil testing does not come under building insurance.

What are the risks if a soil test is not done properly?

It comes down to the footings. If the footings are done wrong, the house is going to potentially move and crack.

For example, if there is fill on the block and a builder tells you it’s fine to put footings in fill and in five years time, you’re house starts cracking and moving – the homeowner will be up for the costs to rectify.

TOP TIP: If there is fill on block, get a compaction report – if the fill hasn’t been compacted DO NOT put in footings and DO NOT be told otherwise.

What’s the average length of time to get a soil test done?

It depends who you go with.

Our name is Soil Test Express so we get our reports out quite quick.

Some companies will turnaround reports in up to 2 weeks, others in 3 to 4 weeks or some within 5 to 7 days.

How about an average cost?

It also depends on the provider. We have a very honest and genuine approach to our pricing.

To give you an idea, people can pay $1,500 for a soil test, we’re $275.

Pricing also depends on what tests need to be done.

We do a variety of testing – Wind Assessment, Bushfire Attack Levels, Footing and Foundation Assessment, Bushfire Attack Level (BAL), Perculation for Stormwater and Land Capability Assessment for wastewater.

When tests are done together, we offer a pricing package.

How do people know whether they need to get other tests?

Generally Council will let you know but again, it doesn’t always work out that way.

An owner may get a soil test done and submitted to Council only for Council to turn around and say you need a BAL test.

That means an owner needs to re-engage us and that costs more money (and time).

TOP TIP: Tell Council what and where you’re building and ask Council what tests need to be done!

If an owner builder engages a draftsperson, a draftsperson can usually advise what tests need to be done.

Alternatively, a soil tester will usually be able to advise what tests need to be done based on the area someone is building.

Finally, what are you tips when it comes to choosing a soil tester?

1. Check for Professional Indemnity Insurance!
2. Be comfortable with the person.
3. Go with someone who is helpful and happy to answer any questions.
4. Customer service – our goal is make the life of our customers as easy as possible. Go with someone who treats you well.
5. Price – we’re mindful of the cost to build a house so we price accordingly. An acceptable cost for a standard soil test (3 ball holes to 1.5m) is $250 to $400.

Well Owner Builders, we hope you found some good nuggets in this Q&A!

And if you're based in Victoria, be sure to reach out to Tracey via her website – click here (you can request a quote) – or via phone (03) 5997 1192.

Tracey's honesty and approach to providing a high level of service to her clients really stood out for us. We highly recommend Soil Test Express services 🙂

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