Poor sub-soil drainage is a leading cause of progressive structural failure. Sub-soil drainage \u2013 the removal of excess water from the soil beneath structures \u2013 is an often-overlooked but critical factor in maintaining the stability of buildings, roads and other infrastructure. This press release explores how inadequate sub-soil water management can contribute to damage, and includes insights from peer-reviewed research and real-world case studies.<\/p>\n
Durban\u2019s geotechnical and climatic vulnerabilities<\/b><\/p>\n
Durban\u2019s subtropical climate is characterised by high annual rainfall<\/a> (over 1 000mm\/year) concentrated in the summer months. Its undulating topography, expansive clay soils (notably the Berea Red Sands) and rapid urbanisation further exacerbate drainage challenges. These factors create a natural predisposition for water accumulation around and beneath structures, particularly in low-lying or poorly graded areas.<\/p>\n According to Brink and Bruynzeel (2018)<\/i> in the South African Journal of Geotechnical Engineering<\/i>, the high plasticity of Durban\u2019s clay-rich soils means they are especially sensitive to moisture fluctuations. When wet, these soils swell; when dry, they shrink \u2013 leading to differential settlement under structures. Over time, this can cause cracks, slab deformation and even foundational failure.<\/p>\n Mechanisms of structural damage from poor sub-soil drainage<\/b><\/p>\n Hydrostatic pressure on foundations and retaining walls<\/b><\/p>\n When sub-soil water is not drained effectively, hydrostatic pressure builds against subsurface structures. In Durban\u2019s Glenwood area, several residential retaining walls have failed following sustained rainfall, where poor drainage led to lateral water buildup. This pressure can displace retaining walls, push basement walls inward and cause foundational uplift \u2013 especially in structures without weep holes or sub-soil drainage<\/a> mats.<\/p>\n Research insight:<\/b> A 2019 paper in the Journal of Performance of Constructed Facilities<\/i> found that 42% of retaining wall failures in wet climates are due to inadequate drainage systems.<\/p>\n Capillary rise and rising damp<\/b><\/p>\n In areas like Berea and Musgrave, where older homes were built with shallow foundations, poor sub-soil drainage has led to widespread rising damp. This occurs when groundwater moves upward through the masonry via capillary action. Without damp-proof membranes or adequate drainage, internal wall surfaces become saturated, leading to blistering paint, mould growth and timber decay.<\/p>\n This is particularly problematic in historical Durban properties, where retrofitting for damp-proofing is complicated by preservation requirements.<\/p>\n Soil erosion and piping<\/b><\/p>\n