What Determines the Foundation Type for a Kit Home?
Transcript
Charles Christodoulou: Yes. What you need to do — your first step — is to organise a soil test. A soil test will determine the type of soil conditions you have, and that in turn determines the depth of the internal concrete beams — or more specifically, both the internal and what we call “edge beams” or the external ones.
If you’ve got a lot of clay in the soil, that would be classified as Type H, which stands for “highly reactive.” This means the soil is highly reactive to water. When it rains, the soil expands, and when it’s hot, it contracts — so you get a lot of movement. The concrete beams need to go deeper into the ground to ensure the slab doesn’t crack.
Better soil conditions would be classified, for example, as Type S — “S” for sand — which means the soil has a fair degree of sand in it. Water filters through the sand, so it doesn’t expand or contract much.
Once you have the soil test, you’ll need to find a foundations engineer. They will design the slab according to the soil test results. If you don’t have a foundations engineer, you can contact us at iBuild, and we’ll check whether we’ve worked with someone reliable in your area and can refer you.
What Decides the Foundation Type?
When planning a kit home build, many ask who decides the type of foundation — slab or stumps. The short answer: it’s not the building surveyor.
It Starts with a Soil Test
The process begins with a soil test.
This assessment identifies the soil’s properties, which are crucial for safe foundation design.
Engineer Designs the Foundation
The soil report is then handed to a qualified engineer, who designs the footings accordingly.
Understanding Your Soil Classification
What About the Building Surveyor?
Only after the foundation design is complete does the building surveyor get involved. Their role is to confirm compliance with regulations and issue the building permit.