Reference Documents - MCU23 0070

How much can the soils under my
house move?
The amount of movement that may occur depends on the site classification,
which is defined under the Australian Standard AS2870.
The relevant classifications and expected movements under normal site
conditions and seasonal influences are:


Site             Description of type of clay and reactivity                   Expected range of
classification                                                                movement
      A          Mostly sand and rock with little or no ground movement       0
                 from moisture changes.
      S          Slightly reactive clays that do not present significant      0 to 20mm
                 trouble. Very limited damage could be expected in the life
                 of the building.
      M          Moderately reactive clays that may cause minor               20 to 40mm
                 movement and damage in the life of the building.
                 Reasonable care is required in planning the site.
      H          Highly reactive clays have potential to move more, and       H1 40 to 60mm
  (H1 & H2)      react to variable moisture change conditions. Some minor
                 damage may occur in the life of the building under normal
                                                                              H2 60 to 75mm
                 conditions. More significant damage may occur where site
                 maintenance conditions are a problem e.g. influence of
                 trees or leaking underground plumbing or poor drainage.
                 Particular care is required in planning the site.
      E          Extremely reactive clays have the potential to react         >75mm
                 significantly to any variable moisture changes in the
                 foundation clays and require significant attention to
                                                                              (Note: Movements
                 detail in planning the site works. Extreme movement and
                                                                              on E sites have been
                 damage may occur if the site conditions and foundation
                                                                              known to move up
                 maintenance requirements are not observed. Footing
                                                                              to and in excess
                 systems and site conditions on “E” sites require very
                                                                              of 100 to 150mm
                 detailed specification from an engineer.
                                                                              in SE Qld)