Site geology & geodesy
When soil investigations are needed, what they provide, and cost
Key questions
When geology is mandatory
Mandatory under building code for CC2/CC3 (>2 floors, complex objects). For a one-storey private house formally optional, but choosing a foundation without it is guessing.
What geology gives you
Soil layers, groundwater level (GWL), bearing capacity (R0), frost heave, optimal depth. This drives the foundation type and its cost.
Work scope & prices
2–3 boreholes 6–10 m + lab + report: ~$400–800. Site topo survey 1:500 — $100–200. Fieldwork 1 day, report 1–2 weeks.
Geodesy
Setting out house axes, tying to boundaries and red lines, control measurements during construction. Separate from geology.
Risks without it
High GWL → floating foundation; heaving soils → cracks; peat/fill → settlement. Foundation repair costs more than the foundation.
How to order
Licensed geotechnical company; the report must include borehole sections, test tables, R0 and GWL conclusion, foundation recommendations.
Geology costs ~0.5% of the house budget but determines 15% of spend (the foundation). A common mistake is copying a neighbor's foundation: GWL and layers can differ 20 m apart.
À propos de Géologie du terrain — quand nécessaire
Géologie du terrain — quand nécessaire — Quand une étude de sol est nécessaire, ce que donnent sondages et labo, coûts, risques sans étude.. Construction: devis, installations, géologie, permis, construction hivernale, réception, assurance, termes. Utilisez nos outils sans inscription ni installation de logiciel. Tous les calculs se font dans votre navigateur — vos données ne sont jamais envoyées à un serveur.