What you Need to Know About the Soil if You are Planning to Buy a Land to Build on


Whether it is for the preservation of a site or for a development or construction project, taking into account the natural issues related to the soil and the environment while respecting the regulations are sometimes the less known conditions for the wide public.

Soil engineering brings together all the sciences and techniques used to characterize a soil (physical, mechanical, and chemical) and, if necessary, to deal with the interaction between construction and its natural foundation. Geomembranes like the ones produced by Atarfil are key when handling proper soil isolation and protect it from possible chemical leaks and contamination.

Geotechnical survey: Taking Action

A geotechnical survey is a study of the soils in your land. It is used for two things; the first is to determine the mechanical characteristics of the grounds which will be brought to support construction. The second is to assess the natural hazards identified in the environment around the land and the impacts that this could have on future construction.

In countries like France, since October 1, 2020, in the event of the sale of non-built building land, a prior geotechnical study (a soil study) must be provided by the seller. This soil study is also mandatory for the conclusion of any contract for the construction of a house.

What is the importance of a soil study?

Carrying out a soil survey aims to avoid drought-related disasters, which are already significant and should continue to get more frequent with climate change. These disasters are caused by the shrinkage-swelling phenomenon caused in clay soils, which affects the integrity of buildings, following episodes of drought followed by episodes of rain.

This problem significantly affects houses, which are usually affected as a result of lighter foundations than robust buildings.

The geotechnical has two clear goals:

  • Preventing the potential risk to the future owner of the land
  • They are giving essential information to the future builder. The company and the engineering team will then be able to offer suitable technical solutions.

Technical solutions to consider

The phenomena of shrinkage and swelling of clay soils have been observed for a long time in countries with a dry climate, where they are the source of many disorders caused both to buildings and roads.

Geomembranes are a thin, flexible product that is used for their waterproofing and chemical resistance properties. They are usually associated with other geosynthetics, and they are the primary waterproofing for almost three hundred dams around the world.

Losses of drought are caused by differential settlements of clayey soils which are sensitive to water variations. By avoiding any water variation, differential settlement, and consequently drought claims are eliminated. The geomembrane is implemented on the periphery of a structure and slightly buried.

Finally, this makes it possible to block the water state of the underlying soils or at least to limit water exchange greatly.

Distance between trees and construction

When trees exist near the proposed construction right-of-way, it is appropriate to take into account their potential influence, namely:

  • Try as much as possible to locate the building outside their “field of action” (generally consider that the influence distance is equal to once or once and a half the height of the tree in adulthood);
  • Cut down disturbing trees as far upstream as possible from the start of work (so as to allow a re-establishment of the natural conditions of the water content of the ground).

Although some species, oaks, poplars, and willows have a known more significant impact than others, it is difficult to limit these measures to these species. A hazelnut tree, an albizia, a birch can also trigger differential settlement.

If the construction cannot be located at a sufficient distance from trees, the installation in place of a vertical screen prevents the propagation of tree roots under construction. This cut will find its place as close as possible to the trees from which it is necessary to protect. The minimum screen depth is 2 m.

This device generally consists of a rigid screen, possibly associated with a geomembrane, placed vertically in a trench. The anti-root screen should be able to present sufficient guarantees of sustainability, in particular with regard to waterproofing and resistance.

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