Delays to contractors' progress, often resulting in time and cost overruns, are a major source of claims and disputes in the construction industry. The assessment of extension of time (EOT) claims as part of a construction project can have far-reaching consequences for the financial success of the project. The proper and transparent assessment of EOT claims is, therefore, an essential component in the success of any project. In this article, an actionresearch approach, a very specific qualitative approach, was followed to develop a userfriendly guideline to help practitioners navigate this potential minefield of complexities in the process of the assessment of EOT claims. Focus groups, consisting of industry practitioners, with specialist knowledge in construction contracts, contributed to the development of the decisionsupport frameworks, and ultimately to the findings. The iterative process followed assisted in producing a tool that can be used in practice as a guideline for the analysis of EOT claims when using the Principal Building Agreement of the Joint Building Contracts Committee (JBCC). Keywords: Construction delays, decision-trees, EOT, JBCC AbstrakDie vertraging van die aannemer se vordering het dikwels 'n negatiewe impak op tyd en koste en is 'n groot bron van eise en geskille in die konstruksiebedryf. Die evaluering van eise vir die verlenging van tyd (VVT) kan tot verreikende nagevolge lei in verband met die finansiële sukses van 'n projek. Die behoorlike en deursigtige evaluering van VVT-eise is dus 'n noodsaaklike komponent in die sukses van enige projek. 'n