There are three key reports that every new home builder should order before committing to a builder’s deposit.
It’s so important to know what you’re getting into before you start building, and these reports will give you incredible detail about the characteristics of your block. Most importantly, the information from these reports can help you work towards getting a fixed quote, avoiding costly surprises and headaches down the road.
Your builder can arrange these tests and reports on your behalf, and it may cost less than you think.
Your building certifier, structural engineer and council will require a soil test to be completed to ensure foundations are adequate to support the new home. However, many people don’t realise that this test can also help you financially.
By far the biggest unknown in building a new home is what’s under the ground. As a result, this is often where the biggest cost overruns come from. Getting a soil test before paying your deposit could possibly eliminate this risk, as you will be able to get more accurate quotes. This could potentially save thousands of dollars in increased site costs later in the process.
The first thing a soil test provides data on is the bearing capacity of the ground. From the data obtained by soil testing, it is possible to know the weight the soil can support per unit area.
This data helps determine the foundation the engineer will need to design for your house. There are established guidelines for foundations and footings, and more unstable land may require deeper footing/slab. Often builders will quote a standard foundation/slab, so a soil test will help them quote more accurately. As footing issues can be costly, getting a soil test before paying your deposit could remove any potential surprises down the track.
Bearing capacity is important for determining foundations sizing, and also the soil’s reactiveness. Soil testing is necessary to get an idea of soil reactivity i.e. 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:
While classes A to S will usually require a basic foundation, all other classes will most likely need additional 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.
A soil test will also help a builder provide more accurate site fill and scrape recommendations. Sometimes a site may have been filled by the developer, or the builder may need to fill the site in order to build the house level. If the fill is more than recommended or not compacted as recommended, this can cause you problems years later. This also applies to how much the top soil on your site can be scraped from your site.
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 pre-development of the site. Depending on the field test some building blocks may require soil samples to be taken for further laboratory testing.
Although soil tests don’t guarantee certainty, they do allow foundations to be designed and priced more accurately.
In addition to a soil test, we recommend getting a site survey done at the same time. A site survey gives you more detail about your block, and will give you the following elements:
A wind rating assessment will give the designer the expected loadings which need to be designed for in the structure to suit wind gusts and speeds relative to your block.
Existing retaining walls on your lot or neighbouring lots can have quite an effect on your foundation design and cost. They can create different loads/stresses in the ground which need to be allowed for.
Building the floor level or levelling the platform on a sloping block is expensive. Having accurate levels done enables this work to be priced more accurately.
To the naked eye a block of land could look flat, but a site levels & contour report will show the shape of the land. Identifying various heights and falls of the block. It may help to identify fill that could have been dumped there during the development or possible underground water courses.
This information will help a good builder to design the correct structure orientation, location for your new home.
As part of this report other items that are often identified include:
The third thing you’ll need before receiving an accurate quote from your builder is a detailed property report. This will complete the picture on what to expect before commencing building on your block. It will help you to make decisions upfront that could potentially prevent delays, complications and additional costs further down the road.
A detailed property report will provide you and your builder with answers to the below questions:
In addition to these important elements, a property report can also provide information about:
A soil test, site survey and property report will give you a lot of information—this can often be overwhelming! A good builder will help you interpret the jargon and incorporate all the considerations into your quote.