Choosing a building site without first having the soil tested can lead to serious problems in the future, so it's never a step that you want to skip. Remember, even other properties in the immediate vicinity don't guarantee the quality of the soil on your site.
One of the most important reasons to conduct soil testing is to ensure that the soil isn't 'reactive'. This might make it sound like it is contaminated; in fact, reactive soil will change volume and shift in response to varying degrees of moisture.
What Does Reactive Soil Do?
Soil isn't made from just one single compound. There are plenty of different compounds that make up each stretch of soil, and some, particularly those with a high volume of clay, can change volume more than others. A building will be designed to deal with some soil movement, but extensive movement can still cause damage. When soil gains volume, it can place pressure against the structure; this will occur during periods of high moisture. When the soil loses moisture, it will collapse back down.
Foundational Problems
As you might well imagine, the most common problems that occur thanks to reactive soil are foundational. The foundation of a building will be able to put up with some movement, but the constant changing of pressure beneath it can cause structural damage, which will in turn lead to additional problems, including slope failure, sinkage, and lateral movement.
Vertical Pressure
As well as putting strain on your foundation, reactive soil will also place pressure upon your walls. When the soil swells, the vertical structures of a building will be put under additional strain. In some cases, at least at first, the signs of damage are quite minimal; owners may find that it becomes harder to open doors or windows, for example. However, pressure can also result in the cracking of masonry walls. This will let more moisture into the property, creating a vicious cycle.
Drainage Issues
Finally, consider what is going to lie underneath a property. Most modern drainage systems are connected up in a way that allows for zero mechanical movement. When reactive soil is swelling or compacting around your pipes, movement is just what they will be subjected to, and the pressure of compact soil around each pipe can also can cause damage. When soil shrinkage or swelling damages your pipes, water or waste will seep out into the sub-soil, which will make existing moisture issues even worse.
