Every construction site, whether a high-rise building or a single-family house, must have a soil test before construction begins. This is because the soil is the carrier that holds the weight of the house. The foundation needs to be designed according to the soil bearing capacity, and therefore the cost of construction becomes uncertain.
In order to get an accurate quote and avoid or reduce these uncertainties, I recommend scheduling a soil test as soon as you have paid a deposit for the land.
How is a soil test performed?
When you schedule a soil test for a building lot, you will need to：
- obtain a site plan showing both the location of the existing building and the proposed building
- send the plans to a soil testing company. A soil testing engineer uses a special device to drill into the ground and extract the soil for analysis. By determining the type of soil at different depths, they will be able to classify the soil and determine the bearing capacity of the soil
- You will receive a written report on the condition of the soil on the site. Send the soil report to the builder/engineer/designer for accurate design and quotation.
Understand the soil report
The information in a soil test report usually includes soil reactivity, soil bearing capacity, soil density, and soil moisture.
The soil report will classify your soil based on reactivity.
Class A: stable, non-reactive: the possibility of very little or no ground movement as a result of moisture change (often sand and rock sites)
Class S: Slightly active clay soils
Class M: Moderately active clay soils
Class H: Highly active clay lands
Class E: Very highly active clay land
Class P: problem sites: ground movement because of moisture change may be very severe, you will need to consult a structural engineer before building a new house.
Many builders only offer fixed site cost for lands in Class M and above.
Soil Testing and House Design
Soil test results can have a significant impact on the design of a building foundation. An engineer will design the type of foundation based on the type of building and the different soil classes.
Different foundations will require a quite different depth and width of excavation, different strength of the steel used, and of course a hugely different cost.
Soil test reports are especially important and determine the cost of foundation construction. I would recommend that you get the soil test report as early as possible so that you can get an accurate quote from the builder and try to get a fixed contract amount from the builder. Integrity New homes Melbourne East can arrange a soil test for you at the preliminary stage.
There is more to explain as far as foundations and design are concerned, if you still have questions about the construction and design of foundations, please feel free to call and write to us.