Design data for slab-on-ground floors based on 0 °C criterion
This annex provides data for the design of shallow foundations for slab-on-ground floors, when the design condition is that the 0 °C isotherm does not penetrate below a 2:1 load spread area beneath the foundation (see Figure C.1).
|1 Ground insulation
4 0 °C isotherm
|2 Non frost-susceptible fill
5 Frost-susceptible soil
|3 Zone of stress influence|
C.2 Heated buildings
C.2.1 Foundations with no ground insulation
The design should conform with 8.3.1, 8.3.2, 8.3.3 and 8.6, and instead of 8.7.1 it should conform with the following.
The foundation depth should be:
- at the walls, at least Hf;
- near the corners and at limited unheated parts for a distance Lc from these places, at least the greater depth Hfc;
where the values of Hf, Hfc and Lc are given as a function of the design freezing index in Table C.1 for fine-grained soils (silt and clay) and in Table C.2 for coarse-grained soils (frost-susceptible sand and moraine). Linear interpolation may be used in these tables for intermediate values of Fd.
C.2.2 Ground insulation all round the building
The design should conform with 8.3.1, 8.3.2, 8.3.3 and 8.6, and instead of 8.7.3 it should conform with the following. The data apply when the thermal resistance of the floor slab is less than 5 m2·K/W.
The width of the ground insulation bc, along the walls and at corners, should be at least 0,8 m.
Determine the minimum thermal resistance of the ground insulation along the walls, Rgw, according to the foundation depth Hf and the design freezing index Fd from Figure C.2.
At corners the thermal resistance of the ground insulation should be 40 % greater than along the walls, for a distance Lc (from Table C.1 or C.2) from each corner.
- 1 Thermal resistance of ground insulation along walls, Rgw
- 2 Design freezing index, Fd
Thermal resistance of floor slab Rf < 5,0 m2 K/W
C.3 Buildings with low internal temperature
For poorly heated buildings with 5°C ≤ θi,m < 17°C, the values of Hf and Hfc in Table C.1 should be increased by 0,3 m.
If θi,m <5 °C in any month, the frost protection of the foundations shall be designed as for unheated buildings (see clause 10).