Why does Soil Type Matter?

Why does Soil Type Matter?

The type of soil you are about to build a home on will determine the slab type needed. The earth under your home is the foundation for your building, it could have an impact on your home over its lifetime. It is important to have the soil engineered and certified by professionals.

What is being tested in your soil?

In basic terms, the engineer with determines your soil’s reaction (movement) to both wet and dry conditions. Your home’s slab type will then be designed, based on these results.

How is the test done?

Two to three boreholes are drilled (usually 2m down) and soil samples are removed and taken to the laboratory for testing. This process will take seven to ten days.

What are the Soil Type Classifications?

  • A – Acceptable
  • S – Satisfactory
  • M – Moderately Reactive
  • H1 & H2 Highly Reactive
  • E – Extreme
  • P – Problem Site (Usually due to trees on site)

E Class soil type and slabs

This is the most extreme soil type and simply means this soil has a higher level of movement. Although E class slabs are the most expensive, the good news is your home will be sitting on a very strong slab and foundation! Interestingly, E-type soil is usually much better for growing lush gardens and turf – saving you money when it comes to landscaping your home.

What do the soil types mean?

  • Soil types of A, S, M, H1 and H2, have the typical specification of ‘nominal/standard waffle design’ from AS2870.
  • Soil types E, the engineer recommends using a conventional, stiffened raft slab with ground beams.
  • Site types of P are looked at on a case-by-case basis as no two sites will be the same. They may determine a need to have concrete piers into the ground.

What type of slab?

The Structural Engineer plays an important role by making the final decision on what type and size of the slab will be used based on the results of your soil test. Generally, the more extreme the soil type, the thicker and stronger the slab and foundations must be.


type of slab