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You have just found the land of your dreams and you already see yourself in your future home... But be careful, depending on its location, depending on the nature of the soil, depending on its environment, the dream can turn into a nightmare. Before committing yourself, pay attention to the characteristics of this building plot that you like so much. You will be able to start the work in all knowledge of causes.

Characteristics of a building plot

Characteristics of a building plot

Take into consideration the foreseeable risks of the building plot

When you really like a field, start by going to the town hall and ask to see the PLU (Local Urban Plan). Not only will it tell you what kind of construction you can do on the field but it will also tell you about the risks that you can run to build on this land thanks to the PPR (Risk Prevention Plan).

There are several PPR:

  • The PPRN or Plan for Preventing Natural Risks: Floods, earthquakes, storms, drought, forest fires, avalanches, landslides, etc.
  • The PPRT or Plan for Prevention of Predictable Technological Risks: Identifies high-risk industrial establishments.
  • The PPRM or Plan for Prevention of Predictable Mining Risks.
  • The PPRS or Plan for Prevention of Predictable Marine Submersion Hazards.

Depending on the region where you will settle, it is important to know his documents because they impose specific construction prescriptions in order to protect you.

Take into consideration the nature of the soil of the building site

You must know the nature of the soil before starting to build and before buying the land. Indeed, depending on the quality of the soil, the type and cost of foundations vary. Do not hesitate to make a geotechnical study or see if the town hall has no geological maps.

Be particularly careful in the presence of swelling clay, heterogeneous soil, backfilled or compressible:

  • Swelling clays: Wet these clays inflate and retract when dry. These movements of soil cause serious disorders in the foundations and important structural cracks. Foundations and constructions must be adapted to best meet these constraints. The Ministry of Ecology publishes a map of areas at risk: argiles.fr
  • Heterogeneous soil or backfilled: The anchoring of a construction in the ground must be homogeneous. But a soil composed of layers of different nature does not allow a homogeneous anchorage. Construction may be destabilized by differential settlements. It is then necessary to look deeper for a carrier soil and to adapt the foundations: foundations in wells, micro piles.
  • A compressible soil: The problem is almost the same as for heterogeneous soils or backfilled because these lands will not support the weight of construction. The foundations must be adapted to avoid differential settlements: solid slab or slab, micro piles. You may encounter this kind of soil at the bottom of a valley for example.

Take into consideration the configuration of the building plot

Looking at this land that you like, try to imagine living in your future home in the summer sun but also in the snow in winter or in the rain... Because between your dreams and reality, there are the constraints posed by the terrain configuration.

  • Build on sloping terrain: It is easier to build on flat terrain than on sloping terrain. It is not impossible but it is more expensive especially if the slope is important. The foundations must be anchored homogeneously. On sloping ground, it goes down deeply into the ground from the top side and can give rise to important earthworks. Likewise artificially creating a flat construction zone makes a lot of land move and poses the problem of construction on heterogeneous terrain.
  • Consider the orientation and the exhibition of the field: The RT 2012 (Thermal Regulation) requires to consider the environment to implement a new construction. Depending on the size and topology of the field, pay attention to how you will build. Optimize solar gain to lower your heating bill and the use of artificial lighting. Take into account prevailing winds that can bring cold and moisture.

By being attentive to the foreseeable risks, to the nature of the ground and the configuration of the ground, you will realize a house adapted to its environment, healthy and durable. To visualize all the foreseeable risks of your land, consult the site georisques.gouv.fr


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