Everything you need to know about geotechnical research

Everyone who wants to start building a single-family house has many tasks ahead of them, which precede the first digging of the shovel into the ground. After the amendments to the regulations in 2012 in most communes in Poland, without their implementation, it is almost impossible to obtain a building permit. However, many investors consider this research to be a waste of time and money. This is a huge mistake.

Geotechnical studies will determine the soil composition

Some municipalities in Poland, despite the regulations, allow the issuing of a building permit without performing geotechnical tests of land intended for a given building. However, even in such cases it is worth to decide on their implementation. Geotechnical studies allow to determine the composition of the soil and its characteristics, as well as the level of groundwater. Such information helps to avoid many unpleasant situations in the future. For example, cracking walls or collapsing foundations are the fault, poorly selected foundations and their insulation, due to the lack of recognition of the area by just conducting the appropriate tests. The new regulations introduced the requirement to carry out geotechnical surveys for all categories, which is why they should be completed before the construction of a single-family house.

What are the geotechnical categories of buildings

There are three geotechnical categories in construction that divide buildings and structures according to their type of use, as well as the soil on which they arise.

First geotechnical category

This category usually includes one or two-storey houses, the foundation depth of which does not exceed 3 meters. In this case, all that is required is a surveyor’s opinion based on geotechnical surveys of the lands located on our plot. However, sometimes it happens that due to the complicated soil profile, buildings will fall into the second category.

Second geotechnical category

This category usually applies to large buildings as well as smaller ones built on complex soil conditions. In this case, in order to obtain a building permit, more thorough soil testing involving the quantitative and qualitative assessment of geotechnical data should be carried out. Studies carried out in connection with a larger scope also have a similarly higher price than in the case of the first category.

Third geotechnical category

This category includes all high-rise buildings and structures that are being built in urban spaces. In its case it is necessary to prepare full geotechnical and engineering documentation. Sometimes, however, also single-family houses that are to be erected in extremely difficult terrain require the performance of such specialized tests.

What is included in the geotechnical opinion

Geotechnical opinion is required for all three categories, depending on the classification, it must only be supplemented with additional information. Geotechnical opinion always consists of a descriptive and graphic part. The description includes information on individual soil layers, groundwater level and possible recommendations for more detailed research. The graphic part is an illustration of the plan of the area under the building. The locations of the boreholes are marked there and it depicts individual layers of soil occurring in a given area.

Who can do geotechnical research

There are many companies in the Polish construction industry that provide geotechnical testing services. However, it is worth remembering that regardless of whether it is only about issuing a geotechnical opinion or carrying out detailed tests and projects, they can be performed only by qualified V and VII grade surveyors who have successfully passed the state examination. However, only qualified geologists can obtain such qualifications.

Many investors downplaying these activities additionally commission the research of the first better company that offers one of the lowest prices on the market. It is worth knowing that the price of tests often results from a smaller number of wells that require time than recommended. However, their smaller number adversely affects the credibility of such studies, and again also the wrong selection of the type of foundation. By what apparent savings, it can translate into huge expenses related to building repairs, even immediately after its construction, and even in extreme cases may result in suspension of construction works.

That is why it is worth looking for reliable companies that drill at least three wells, and preferably four, in places where the corners of the buildings are to be located in the future. Especially if it is to be a basement, and the investor wants to avoid unpleasant flooding of the basement during periods of increased rainfall or spring thaws.

To sum up, performing geotechnical tests according to the 2012 regulations is almost always required in our country to obtain a building permit. It is not worth saving on its execution, and it is also worth doing it even when the given authority does not require submission of a geotechnical opinion along with the application, because the average cost of PLN 15,000 translates into long-term operation of the building unscathed.