A Home Builder’s Guide to Soil Types

A Home Builder’s Guide to Soil Types

Soil type is a vitally important consideration when building a home. Some of the key questions we get from our clients include:

  • Why is soil type so important?
  • What on earth do those letters even mean e.g. Class M, Class A?
  • How do I find my soil type?
  • How much does the soil type affect the cost of my home?
  • Can I use a neighbouring property’s soil test results?  
  • Why is my soil test different from the house next door?

These are all questions that we hear daily from our clients as a new home builder on the Gold Coast. I am sure all builders everywhere hear the same questions! In fact, unless you’ve built a house previously or have experience in the building industry, most people would have no idea about the importance of soil testing. So we thought we’d try and explain what it all means….

Soil Type Determines Type of Slab Required

Before a house can be built, we need to make sure we know what type of ground it’s being built on.  We want our houses to be strong, and stand the test of time. Nobody wants their house to have a cracked slab in 5 years or cracks in the ceiling and walls!  

Ensuring our homes have the correct foundations to secure them into the land they sit on, is one of the most critical factors in the planning and building process.      

Water and its Interaction with Soil

Commonly water is the greatest issue when it comes to long-term building defects. Reactive soils absorb water and change in volume. Water can also cause erosion of some soils which may result in subsidence of foundations and building damage.

For this reason at Stroud Homes Gold Coast, we always recommend to clients that when purchasing a block of land, that they make the contract with the seller subject to soil testing. Soil tests cost around $500 and take up to 14 days. If your soil test was to come back as H, E or P,  you then have an opportunity to explore your options before being locked into purchasing a block that may cost you up to an extra $15000 to build on!  

Soil Types Explained

So what do the letters mean?

CLASS A Acceptable Mostly sand and rock with little or no
ground movement from moisture changes
CLASS S Satisfactory Slightly reactive clay sites with only
slight ground movement from moisture changes
CLASS M Moderate Moderately reactive clay or silt sites,
which can experience moderate ground
movement from moisture changes
CLASS H1 &H2 Highly reactive Highly reactive clay sites, which can experience
high ground movement from moisture changes.
CLASS E Extreme Extremely reactive sites, which can experience
extreme ground movement from moisture changes.
CLASS P Problem Sites which include soft soils, such as soft clay or
silt or lose sands: landslip: mind subsidence:
collapsing  soil: soil subject to erosion:
reactive sites subject to abnormal moisture
conditions or sites which cannot be classified otherwise

Free Site Evaluations

Our team at Stroud Homes Gold Coast can organise a site inspection prior to your purchase, give you advice on the area, and arrange soil testing to be carried out. Once the classification report is received it will be used to plan building site preparation and provide site-specific information to assist in appropriate foundation design.  Knowing what extra foundations costs may be required will allow us to accurately quote your build so that you can secure your budget and financing.