Assessment of the Impact of Design Changes on Project Duration and Cost in Building Projects in Asaba, Delta State

Design changes during construction are a major source of cost and programme disruption on building projects, yet their systematic management remains inadequate in many Nigerian construction environments. This study assesses the impact of design changes on project duration and cost in building construction projects in Asaba, Delta State. A quantitative survey design was adopted, with 80 quantity surveyors, architects, and contractors working on residential and commercial projects in Asaba forming the respondent group. Structured questionnaires were administered and data analysed using correlation analysis, mean scores, and frequency distributions. Findings show that design changes account for an average of 11.8% additional cost on sampled projects, with programme extensions averaging 23% of original duration per design change series. Client-initiated changes (38%), design errors (29%), and site-identified discrepancies (21%) are the leading sources of design changes. The study establishes a strong positive correlation between design change frequency and both cost overrun and programme delay outcomes. Projects with formally documented change management procedures demonstrate better cost and time performance than those without. Recommendations include adoption of formal change request and approval procedures for all building projects above a defined value, implementation of design freeze protocols after client sign-off, and use of BIM-integrated clash detection to minimise field-identified discrepancies. This research adds to cost and time management literature for the South South geopolitical zone. Keywords: design changes, project duration, project cost, Asaba, construction management