Alleviating the problem of cracking of masonry buildings on expansive clay by building flexibility into the masonry

Abstract

Damage caused by soils subject to change in volume beneath light structures, particularly low-cost housing units of masonry construction, is unacceptably frequent. It has led to the demolition of many such units within a small fraction of their design lifespan. Perhaps the most spectacular such failure is Lerato Park in Kimberley, where the development was demolished within four years. The reason for this failure is examined in Stott and Theron (2016). The normal ways of attempting to reduce heave damage have involved increasing the strength and stiffness of foundations, together with reducing masonry panel size through movement joints and increasing the strength of the panels. While these measures have improved the situation somewhat, they are expensive and have proved to be only partially successful. This investigation examines the possibility of increasing the ability of masonry panels themselves to accommodate significant distortion without sustaining unacceptably serious cracking. The existing specifications in SANS 10164 (SANS 10164 2000) are shown to allow considerably greater inherent flexibility than current practice allows. This is dependent on the specified quality of sand (frequently ignored) and water demand requirements, as specified in South African standards, being adhered to.