Document Type



Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence


Architecture engineering, Construction engineering


Cost overruns are commonplace during the construction phase of building projects. This study investigates common reasons why cost overruns happen on building projects. It examines how the client’s priorities and decisions regarding the project duration and quality expectations can undermine cost certainty. The actions of the client’s consultants, particularly those of the architect / employer’s representative, are identified as key factors in causing or preventing cost overruns. The building process, itself, is uncertain, particularly in relation to ground conditions. Large, complex and innovative construction projects containing a substantial element of specialist work are identified as ones which are particularly prone to cost overruns. The study outlines the impact of procurement decisions on cost certainty, noting in particular the likely response of contractors where under-priced work has been tendered and accepted.

Incomplete or poor design and poor tender documentation were identified as weaknesses which bring about the need to introduce an excessive number of variations. Similarly, failure to provide cover for excusable and compensable risks and market factors may also lead to overruns. Poor performance of management tasks, administrative duties, and slow decision making were also discussed in the context of creating difficulties in controlling costs.

Avoiding cost overruns requires an effective plan which recognises these problems and exploits the ability of the quantity surveyor to effectively manage them. This study is addressed to Irish students undertaking studies on undergraduate and conversion masters courses in quantity surveying and construction management related disciplines.