Foundations The function of a building foundation can be summarised as follows: To transmit the combined dead, imposed and wind loads from a building to the soil on which the building rests in such a way that settlement, particularly uneven or differential settlement, of the structure is limited and failure of the underlying soil is avoided.

Loads Dead load - the weight of the building itself.   Dead load - the weight of the building itself. Imposed load - the weight of the contents of the building. Wind load - the force of the wind acting upon the building which may be positive or negative.

Differential Settlement Where settlement occurs due to soil consolidation at different rates beneath different parts of the building. Causes cracking which may be minor, but could result in damp penetration or structural damage.

Wind Pressure

The Traditional Strip Foundation Used below load-bearing walls where soils have good bearing capacity and loads are relatively light.

Materials   Traditional materials were ash, stone and brick. Today we use concrete, typically a GEN1 or ST2 mix as described in BS8500 Part 2 Building Technology

Design Issues Width (w) should suit soil conditions and loading.   Width (w) should suit soil conditions and loading. Depth (d) should suit soil conditions, normally not less than 750mm. Thickness (t) min 150mm, typically, 225 or 300mm Wall should be positioned centrally.  Projection (p) each side of the wall should not exceed t.

 

The Deep Strip Foundation Very commonly used – reduces time spent in the ground. The same rules apply with respect to dimensions.