Ratios for cost control

The design of buildings takes place in phases representing a development from rough to precision planning. Estimates are made in order to test whether the result is still within the budget set by the client or developer. In this way, the decisions taken during the design phase can be quantified and expressed in monetary terms. To prevent blaming the wrong person when an overrun is discovered, the cost control process has to be improved. For that purpose, two new procedures have been developed: (i) a new 'translation' activity; and (ii) ratios by which quantities can be characterized. 'Translation' is the opposite of estimation. A monetary budget is converted - 'translated' - into quantities, reflecting the desired quality of the building materials. The financial constraints of the client are thus converted into quantities - the building components used by the designers. Characteristic quantity figures play an important role in this activity. In working out an estimate, the form factor (i.e., the ratio between two characteristic values of a building component) has to be determined. The unit cost is then tested against that ratio. The introduction of the 'translation' activity and the use of characteristic quantity figures and form factors enhance existing estimation methods. By implementing these procedures, cost control becomes considerably more reliable.