Overview
EN ISO 13793:2001 - "Thermal performance of buildings - Thermal design of foundations to avoid frost heave" (CEN adoption of ISO 13793:2001) provides simplified, practical procedures for designing building foundations so that frost-susceptible ground beneath foundations does not freeze and cause frost heave. The standard covers both slab‑on‑ground and suspended floors, and applies to heated and unheated buildings in climates where the annual average air temperature is above 0 °C. It does not apply to permafrost areas, cold stores, ice rinks, roads or buried services (e.g., water pipes).
Key topics and technical requirements
- Design objectives: ensure ground below foundations remains unfrozen during design winter (the standard uses a criterion where soil is considered fully frozen at about −1 °C).
- Four principal protection strategies:
- Place foundations deeper than frost penetration depth;
- Excavate frost‑susceptible soil and replace with non‑susceptible material;
- Add insulation (vertical edge insulation and/or ground insulation) to prevent frost penetration;
- Use building heat or special heating measures (usually combined with insulation).
- Scope of methods:
- Prescriptive tables and graphical data for common cases (clauses 8–10) for quick design of slab‑on‑ground and suspended floors.
- Numerical calculation methods (Annex B) for complex situations, non‑standard soils, or when heating in the ground/floor is present.
- Ground and material assumptions: the standard provides representative thermal and physical properties for frost‑susceptible soil to be used when site‑specific geotechnical data are not available (including thermal conductivities and dry density). If actual soil properties differ substantially, numerical calculations are recommended.
- Important design parameters: freezing index, frost depth, foundation depth, thermal resistance of floor/edge/ground insulation, floor insulation position, and building geometry.
- Normative references: links to ISO methods for thermal resistance and thermal bridge calculations (e.g., ISO 6946, ISO 10211-1, ISO 10456).
Applications
- Designing shallow foundations and floor/edge insulation to prevent frost heave in residential, commercial and industrial buildings (except cold stores/ice rinks).
- Choosing insulation type, thickness and placement (vertical edge vs. horizontal ground insulation).
- Evaluating retrofit solutions where shallower foundations are desired or where soil replacement is impractical.
- Combining thermal design with geotechnical reports to reduce frost‑related settlement risk.
Who should use this standard
- Structural and geotechnical engineers
- Building envelope and thermal designers
- Architects and energy consultants
- Contractors and façade/foundation specialists
- Building authorities and code officials assessing frost protection measures
Related standards
- ISO 6946 - Thermal resistance and transmittance calculation
- ISO 7345 - Thermal insulation definitions
- ISO 10211-1 - Thermal bridges calculation methods
- ISO 10456 - Declared/design thermal values
Keywords: EN ISO 13793:2001, thermal design of foundations, frost heave, freezing index, ground insulation, vertical edge insulation, slab‑on‑ground, suspended floors, frost protection.