At first glance the site preparation for your new home may seem like quite a simple step in the building process, but getting this stage correct is a crucial step to ensuring that your new home remains secure, stable and safe.
Before your new TR home is delivered
A good foundation for your home begins with having a soil report carried out by an engineer that specialises in Geotechnical Reporting. The engineer will retrieve soil samples from in and around the area of where the house is intended to be and they then send the soil samples to a laboratory for testing. The lab will then determine the soil classification (A, S, M, M-D, H, H-D, E and on the odd occasion P class) in accordance with the Australian standard AS2870. The different soil classes relate to the difference in the movement of the soil.
Typically soil with higher clay content will result in a higher soil classification as clay will absorb water in the wetter months but when it dries out it will shrink (think of the surface of a salt lake – the top layer has shrunk as it has dried leaving a brittle, cracked surface). It is this expansion and contraction of the soil that needs to be measured so that we know what measures need to be taken to combat the movement.
Once the results are in, the engineer will then provide us with a site classification report advising of the classification for that particular property, and what is required to ensure the home has the required foundations.
In most cases the site is classed as an ‘A’ or ‘S’ site. This means the home requires our standard 160mm high x 600mm diameter concrete disc footings (also known as concrete plinths, mushroom footings, concrete rings or doughnuts). Higher soil classifications will require strip footings as well, to an extent specified by the engineer.
The TR Homes Drafting team then use the report and the engineer’s requirements to complete the working drawings so that the structural engineer can sign and approve the plans, ensuring that the strip footings, if required, are adequate. Below is an example Region A (non-cyclonic area) – M class site with 300mm deep strip footings.
The next important step to a good foundation is the preparation of your home site which is carried out by an earth worker. TR Homes will always recommend that you include the earthworks as part of your contract so that we can control the works to ensure that this is completed to the correct standards. We will send a reputable earth worker a copy of the plans, the soil classification provided by the engineer, relevant pages from the structural engineering, and our own Scope of Works and request a detailed quote.
Once we receive the quote from the earth worker, we will then carefully check through and ensure that they have allowed for all of the relevant requirements. When we are satisfied that all of our requirements have been met, your supervisor will issue the works to the earth worker and give them a particular date on which we would like him to start. The supervisor will consider many factors before deciding the best time to start the earthworks including but not limited to: location, the time of year, expected rainfall, site conditions and soil conditions. After all, we don’t want all of the hard work and effort to be washed away by seasonal rainfall or blown away by the wind!
If required, the next critical step to ensuring that your foundations are ideal is strip footings. Again, TR Homes will always recommend that you include these as part of your contract so that we can control the works to ensure that this is completed to the correct standards. We send a copy of the plans to a reputable concrete worker along with the soil classification, relevant pages from the structural engineering, and our own Scope of Works and request a detailed quote.
Once we have received the quote and we are happy that all of the relevant requirements have been met the supervisor will again issue the works to the contractor with a start date.
Upon completion of these pre-house earthworks and any required strip footings, the supervisor or a TR Homes representative, will check the finished product to confirm that the works have been carried out according to our requirements and that the site is ready for the house delivery.
After your new TR home is delivered
Once the house has been delivered and the plumbers have finished their required connection underneath the home, the supervisor will coordinate the earth worker to return to complete ‘Backfill’ earthworks. Although it may appear that the backfill is one of those things that can be completed at a later date, it is actually very important that this be completed soon after the delivery of the house. This avoids any water washing the soil away from underneath the disc footings or the strip footings. If this were to happen, the structural integrity of the footings may be compromised.
More ways to ensure your home foundations are kept in the best condition
There are many other factors that can assist in ensuring that your foundations are kept in the best possible condition, including but not limited to: redirecting stormwater away from the base of your home, only having plant species that require light watering and do not have invasive root systems around the base of your house, monitoring existing trees to prevent their roots from interfering with the footings, and ensure that any future excavation around the footing locations is done under the guidance of an engineer.
A final note from TR
If our clients choose to complete any portion of their own site works we will always recommend that this be carried out through a reputable, professional earth worker (and concrete worker if applicable), and that both the client and the contractor liaise with our TR Homes Construction Department prior to undertaking any works to ensure the foundations are stable for the lifetime of the home.