Quantifying construction claims using the differential cost method

In all construction claims there exist two hurdles which must be overcome before resolution can occur, i.e. entitlement and quantification. This paper addresses the latter issue (regarding productivity/impact claims) by initially presenting the differential method of quantification and then describing its application on a case study. Through this method the authors quantified a contractor’s loss of productivity on a four-storey commercial building in western Canada. This was achieved by comparing productivity between a period of construction during which the contractor alleged concrete operations were completed under 'normal' conditions and a period when the contractor's productivity was affected by inclement weather. For proper application of this method, certain requirements must be met. The difficulty in satisfying these requirements frequently causes the result of the calculation to be suspect. The author's compliance with these requirements will be discussed.