The construction cost estimating process is difficult and complex. Decisions have to be taken in the face of uncertainties relating to cost and quantities of production; the production period and foreseeable constructional problems. The difficulties in estimating are compounded in maintenance work due to the following distinguishing factors of the work:

• Small, generally non repetitive and multi-location jobs/tasks
• High labour content in the work; vulnerable to quality and productivity issues
• Higher material wastage due to small work parcels
• Little benefit of learning curve due to nature of work
• Lack of reliable cost standards and data to guide the estimator

The higher ‘uncertainties’ in executing and managing maintenance work has led to higher variability in cost estimates. The variability is further amplified in maintenance tenders as contractors adopt different risk management approaches and commercial considerations in bid submission.

It is important that cost estimates are accurate. From an Owner’s viewpoint, the estimates form the basis of derivation of long life cycle budgets and shorter term budgets for work procurement. From a contractor’s viewpoint, the estimate will form the basis of a tender bid. For both Owners and Clients, the estimate forms the basis of approval of star rates for variations and non-standard work which often occurs in maintenance contracts.