4.2.12 Method of assessment of foundation depths using charts
Foundation depths shall be determined to prevent excessive movement due to ground heave.
A detailed method of assessing foundation depths of up to 2.5m using Charts 1-3 are given in the worked Example of clause 4.2.14 of this chapter.
Table 10 can be used in determining the D/H ratio needed for use within the charts, where:
D is the distance measured from the centre of the trees or hedgerows to the face of the foundation and
H is the appropriate height of trees (mature or actual, depending on what is being assessed).
Table 10: Determination of D/H value
Chart 1: Soils with HIGH volume change potential – Modified Plasticity Index 40% or greater
Chart 2: Soils with MEDIUM volume change potential – Modified Plasticity Index between 20% and less than 40%
Chart 3: Soils with LOW volume change potential – Modified Plasticity Index 10 to less than 20%
Last updated: 3rd January 2024