Before you start building new homes on a piece of land, ensure you factor in enough time to have the soil tested. Proper testing can prevent you running into potentially costly problems when you begin laying the foundations, as the results can allow you to plan for necessary additional measures to your build, such as extra foundation supports or laying deeper foundations.
Local government agencies may hold information from previous soil surveys on the land you intend to build on, but soil erosion levels, runoff and composition can change over time, so it's best to get an up-to-date soil test carried out before building. Here's an overview of the testing process and what you can learn from testing:
The Testing Process
Soil tests are carried out by geotechnical engineers. Samples of the soil are taken by boring holes into the ground at different depths. The reason for boring holes deep into the soil rather than simply taking samples from the top is to check the bedrock and test the water table, which can provide valuable information about the soil's moisture absorption properties. Once the engineer has written their report detailing all of the compounds found in the soil, they will lay out their recommendations for overcoming any problems that have been uncovered. These recommendations may include installing additional drainage or grading the soil.
What Can Testing Tell You
The goal of soil testing is to determine whether the site you're going to build on has strong or weak soil. Strong soil can withstand being built on without becoming compacted. It doesn't respond to moisture by contracting or expanding, which makes it a suitable medium for laying house foundations on. Weak soil does change in response to moisture, which can compromise foundations over time.
Additionally, weak soil can compress when significant weight is placed on it and can be prone to erosion. Aside from determining how the soil will respond to moisture changes and weight, soil testing can show whether there are contaminants in the soil that would make the site unsuitable for building homes on due to the risk to human health. Examples of toxins that could be uncovered include arsenic, cadmium and lead. Toxic soil can't be cleaned, so uncovering contaminants before you begin building can save you time and money.
When you are arranging a pre-build soil test, ensure the engineer is fully informed about the use of the site, the plans for foundation laying and whether there's likely to be any expansion into surrounding land. This will help them understand where on the site to test and allow them to tailor their recommendations to your project.