Before the foundation is built, it is necessary to know what it will be poured into. Literally. A geotechnical expertise is a document that describes what the layers of soil under your plot are made of and whether they are suitable for the planned investment. This is the basis for anyone who wants to build risk-free and in accordance with the regulations.
Geotechnical expertise (also called a geotechnical opinion or soil survey) is a technical study that determines the type, condition and arrangement of the layers of the earth at the site of the planned construction. It follows which foundations can be used, how deep they need to be laid, whether additional protection is necessary, e.g. against groundwater. For the investor, this document is invisible, but for the designer of the structure it is absolutely crucial.
Does it have to be done always? In most cases, yes. Since 2021, the geotechnical opinion is a mandatory element of the construction project for single-family residential buildings. Even if the office does not require it, it is still worth ordering it, thanks to this you will avoid surprises such as boggy ground, high groundwater, peat or unstable embankments. Such situations can not only increase the cost of construction, but also endanger its durability.
The soil survey is carried out by a licensed geotechnician. On the plot, wells are carried out - usually 2-3, to a depth of 2 to 3 meters. Then the documentation is created: a description of the layers, cross-sections, bearing capacity parameters, land classification, groundwater level and recommendations for the designer and the construction manager. It is on the basis of these data that the foundations are designed. Imagine: an investor buys a plot on a slight slope. Great view, good access, everything looks perfect. But after the start of work, it turns out that under the surface there is a layer of soft, watered soil. The foundations begin to settle unevenly. If geotechnical studies had been carried out beforehand, the problem would have been known and the design could be adjusted immediately.
Often the question arises: is geotechnical expertise necessary if the plot looks “dry”? The answer is: appearance is not enough. The ground can be heterogeneous, and problems often only become apparent after excavation. Therefore, it is worth investing in a study - the cost of basic development for a single-family house is usually in the range of 1000 to 1500 PLN net, depending on the location and scope of work. This is a small expense on the scale of the entire construction, and can save you from much higher costs in the future.
