A site classification is a report under AS 2870 that describes how reactive the soil on your block is and how much it may move with changes in moisture. The building rules generally call for it before residential footings and slabs are designed, so your builder and engineer generally cannot finalise the slab without it. With Griffin's median age at 29, many owners may be building for the first time, so it is normal not to know this step exists. We test your block and give your engineer a result from our NATA-accredited lab.

The QBCC guide describes Class M as moderately reactive clay with roughly 20 to 40 mm of movement, while H1 and H2 are highly reactive. The more the ground can move, the more the slab and footings generally need to resist it, which is why a higher class can add to construction cost. We cannot quote your build cost, but the letter on our report gives you a clear starting point for the slab conversation with your builder. Later landscaping, drainage and plumbing also affect how a slab performs on reactive clay.

Yes. A new residential slab generally needs an AS 2870 site classification, wherever the block sits. Griffin lies on the northern shore of the Pine River, and ground conditions can vary across the suburb, so a result from a nearby lot is not a safe substitute for your own. We sample the ground near your proposed footings and test it in our own laboratory, so the report reflects your block specifically. If your lot is close to the river, also look at the council's flood hazard overlay mapping.

Look at two things. First, the Bureau of Meteorology has described the Pine and Caboolture river systems as susceptible to flash flooding, and City of Moreton Bay's flood hazard overlay maps identify areas at risk to guide development. Second, the ground itself: how reactive the soil is where the house will sit. Our classification covers that ground question only and says nothing about water. Reading the overlay mapping next to the report lets you and your builder settle the house position with both in view.

It depends on the contract, so read it or ask your builder directly. First-time builders are often unsure who is meant to order it. Either way, the engineer generally needs the site classification before the slab and footings can be designed, and the certifier relies on that design. If the job falls to you, order the test once you have a block and a builder, before the slab design is signed off. We just need clear access to the proposed footing area so we can test where the house will sit.

At the 2021 Census, 72.2% of Griffin's 4,481 private dwellings were separate houses. For a typical detached home on its own lot, the classification is about the ground under that one slab. Reactive clay is common under Queensland homes, and conditions can vary across the suburb, so a neighbour's report does not transfer to your lot. The test itself does not change with the house type; what matters is sampling near your proposed footings and analysing those samples in our lab.

Our team travels to your Griffin block from our Wamuran base. We work near the proposed footing area, so clear access there helps the visit run smoothly. The soil samples then go back to our own laboratory, which has been NATA-accredited (No. 15070) since 2004. The result is an AS 2870 classification your engineer can use for slab and footing design. If the class letter on it is new to you, the explanation of S, M, H1 and H2 on this page is a good place to start.