Technical Factors Influencing Decisions to Select Underpinning on Shrinkable Clay

While the tendency for clay to shrink in dry weather and to damage buildings has been known for more than a century, the post‐war work of the Building Research Establishment and recent availability of insurance funds to pay for rectification of subsidence damage have led to a focus on this aspect of building failure, where millions of pounds are spent annually. At some point in each case a decision is made as to whether underpinning is required or not. Reports results of a survey of the technical factors which engineers consider when making a decision of whether to recommend underpinning. Analysis of the data indicated that only one factor, the quantity of damage, significantly influenced the under‐pinning decision.