ABSTRACT
Technically, the concept of the observational method (OM) to deliver benefits through careful observation during construction is inherently natural and practical. The use of the OM to enable the safe replacement or stabilisation of old structures is also likely to become increasingly important, given the extensive and ageing infrastructure in many countries worldwide. The stabilisation of the leaning tower of Pisa is a compelling example of how an application of the OM through progressive modification helped to successfully address the stabilisation of an ancient monument of international importance. The introduction of the OM within such a contract immediately presents commercial risks from the need to allow design changes during construction. Such risks tend to fall predominantly upon the contractor who can consequently be exposed to the double disadvantage of less return but more ownership of the design.
