With any new home design, GJ Gardner Homes arranges a number of inspections of the proposed building block. The most important being the geotechnical testing of the site, commonly known as a soil test or lot classification. Soil testing occurs in the first stage of building, where soil samples are collected from your block of land. It is compulsory to have a soil report before any new home design, as the soil profile of land contains crucial information.
So what’s the big deal? Why is soil testing important when building a house? And how is a soil test performed?
Understanding the subsurface soil layers is key as it provides essential information for the engineer to design the house slabs and footing as well as necessary documents for the certifier and council. From the data obtained by soil testing, it is possible to know the weight the soil can support per unit area which in turn determines the footing the engineer will need to design for your house. For example, more unstable land may require deeper footing. As footing issues can be costly, these inspections are done upfront to remove any potential surprises for the homeowner.
There are also further safety reasons as to why soil testing is important when building a new house. Primarily, soil testing is necessary to get an idea of soil reactivity, the likelihood of the soil moving, contracting or expanding. Additionally, soil testing allows professionals to check for any physical or chemical abnormalities on site that may pose a risk to your house in the future.
Soil reactivity is graded by class as follows: A – Non-reactive, stable S – Possible light movement M – Possible moderate ground movement H – Possible high ground movement E – Possible extreme ground movement P – Problem site
While classes A to S will usually require basic footing, all other classes will most likely need reinforcement. Problem sites are extremely prone to ground movement, hence you will need to discuss your options with a structural engineer before building anything on this kind of land.
Soil testing is a task performed by geotechnical engineers. They utilise specialised equipment to drill into the ground and collect samples at various depths. Upon further analysis, it is possible to classify the site and get a soil report outlining any conditions.
Each site is tested individually as you can’t rely on what’s been built on neighbouring properties as a guide or what’s happened during predevelopment of the site. Depending on the field test some building blocks may require soil samples to be taken for further laboratory testing.
Mark Eddie from GJ Gardner Homes Newcastle is currently building homes on a subdivision that had 21 sites tested by Ideal Geotech. The majority of the building blocks were identified as “M” class sites with some becoming “P” sites due to the depth of fill. One block was identified as a “H1” class with higher reactive soil after laboratory testing was completed. All sites are comfortably handled with the engineer designing the appropriate slab and footings. Over the 21 building blocks the soil condition varies but once construction has been completed each house has been designed and built to suit it’s soil class.
Ideal Geotech captured a video highlighting the work carried out on this site, which also gives a view of the overall subdivision.
If you want to start your home journey or have any questions around the inspections of your proposed building block contact your local G.J. Gardner Homes office. They’ll help you through the journey and make your dream a reality.