Soil Test Before Building

Why is getting a soil test before building so important?
If you do not build your home on firm foundations, it’s not going to be structurally sound. Testing the soil is an important part of making sure foundations are solid because different types of soil react in certain ways. This is why soil testing by geotechnical engineers, needs to be carried out before you get your building permit.

Why is the type of soil so important?
The fact is that there are several different types of soil, and soil type can have a significant impact on any building project. For instance, some soil contains high levels of minerals such as smectite clays. These minerals can easily absorb water which causes them to expand.

The more expansion there is, the more likely there is to be damage to any foundations which are laid. This is why you need to know if the soil where you are planning to build is expansive. If this is the case, the building plans can be amended to include a solution to the problem, such as wetting the ground so that expansion happens before building commences.

Soil can also contain high levels of salt which can cause metal structures to corrode, if no preventative measures are taken. Measures can include ensuring that drainage is effective, as salts usually need to react with moderate levels of water in order to cause corrosion.

How groundwater can contribute to problems with ground movement
High groundwater levels can also be an issue as they can cause soil to move in an unsafe manner. They can also lead to damp conditions in the basement and crawl spaces of a property, if the problem is not addressed before building begins. As with the issue of high salt levels, an effective drainage solution can help with high groundwater levels. There is also the possibility that damaged underground water pipes could be causing the issue, so this may require investigation.

Issues with moisture change are a major concern, especially when high levels of groundwater combine with expansive soil. Having the soil tested before you build enables you to know what class of soil is present on your land, and how likely it is to move.

What are the different classes of soil reactivity?
There are six main classes of soil reactivity. There is more likely to be a significant amount of ground movement with certain classes.
– Class A Stable soil where there is likely to be no movement, or only a small amount. This type of soil often contains sand or rock.
– Class S A small amount of movement may occur in these soils which often contain clay.
– Class M Moderate movement is possible in these soils where clay and silt is often found.
– Class H High levels of ground movement can happen in these soils which are often clay based.
– Class E Ground movement may be extreme.
– Class P Problems with ground movement could be extreme and the expertise of a structural engineer is needed before any building work can start.
You should never try and judge soil for yourself. An expert needs to carry out soil testing and produce a report for you.

Who carries out the work and what do they do?
All soil tests should be carried out by a qualified geotechnical engineer. They have the expertise required to carry out the work and compile the soil test report which is normally required to get a building permit.
Geotechnical engineers examine the area of land that is to be built on and note the general characteristics of the soil. This includes noting the level of groundwater present. They take samples of the soil and groundwater, to be sent to the laboratory for testing. Once the results of the testing are known, it’s up to the engineer to analyse the results and compile a comprehensive report.

What is included in the soil test report?
This report includes the results of the analysis and details of any particular issues that have been identified. The engineer also provides advice about steps to take to resolve these issues, and eliminate potential risks. The information in the report is used by architects and construction professionals to create or amend plans for a building project. It can also be used during the construction process.

You can see why soil testing is so important. You need to know how reactive the soil is, so that you can determine how safe it is to build on the land. Geotechnical engineers are experts in carrying out soil testing, so the process is simple and does not take long. Do not forget that discovering the soil is less than perfect does not necessarily mean you cannot build. It means that you may need to consult a structural engineer before you continue, so that you have complete peace of mind.

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