What is Compare My Build?

An interactive comparison platform for home buyers to evaluate builders, plans, and inclusions in their region side-by-side.

Who pays for a site classification report?

In most cases, the buyer is responsible for obtaining and paying for the site classification report before signing a building contract. Some builders include it in their preliminary costs.

How long does a site classification report take?

Typically 1–2 weeks from when the test is conducted. Ordering early is recommended as it can affect your slab budget significantly.

What site classifications are there in Australia?

AS 2870 classifications are: A (stable, sandy), S (slightly reactive), M (moderately reactive), H1 (highly reactive), H2 (very highly reactive), E (extremely reactive), and P (problem soils).

Free for home$Spot costly upgradesCompare real builder

Free for home buyers$Spot costly upgradesCompare real builder inclusions

Home›Build Knowledge Hub›Building Process›Slabs & Siteworks›What Is a Site Classification Report?

Slabs & Siteworks

What Is a Site Classification Report?

Before your builder can design your slab, a geotechnical report must determine your soil classification. Here's what it covers and why it matters.

5 min·Compare My Build — Independent Resource· Updated June 2025

Introduction

A site classification report is a geotechnical assessment of your land that determines how reactive the soil is and what kind of slab or foundation your new home requires. Under Australian Standard AS 2870, every new home must have an appropriate slab design based on the site classification — making this report one of the most important early steps in your build.

What Does a Site Classification Report Cover?

Component	What It Assesses
Soil reactivity	How much the soil swells and shrinks with moisture changes
Bearing capacity	Whether the soil can support the weight of your home
Groundwater depth	Risk of flooding or moisture affecting the slab
Fill material	Whether the site contains engineered or uncontrolled fill
Site classification	Final rating: A, S, M, H1, H2, E or P class

Cost Comparison

Basic site classification report$500 – $900

Full geotechnical investigation (complex sites)$1,000 – $2,500

M class site slab$8,000 – $14,000

H2 class site slab (vs M class)+$8,000 – $20,000+

The cost of the report is small compared to the slab cost difference between classifications. Never skip this step.

Common Builder Inclusions

›Most builders require a site classification report before finalising a quote
›The report cost is typically paid by the buyer as part of preliminary expenses
›Some builders include a site test allowance in their initial quote — confirm in writing
›If classification comes back higher than assumed, site costs will be charged as an extra

Common Trap

Some buyers receive a builder quote before getting a soil test. If the soil report returns a higher classification than assumed in the quote, you could face $10,000–$25,000 in additional site costs after signing.