Which term would be used to describe a project that incurs extra expenses due to extended tenant improvements?

The term that accurately describes extra expenses incurred due to extended tenant improvements is escalation costs. These costs represent the increase in expenses over time, often resulting from delays or lengthy construction schedules. In the context of tenant improvements, if a project takes longer than initially planned, the costs can increase significantly due to various factors, including inflation, rising labor costs, and extended utilities for the site.

Contingency costs are typically a percentage of the total project cost set aside to cover unforeseen expenses, but they are not specifically tied to tenant improvements. Add alternates refer to additional items that can be added to a project if the budget allows but are not directly related to cost increases due to prolongation. Fixed costs remain constant over time regardless of project duration and wouldn't encompass additional expenses incurred from tenant improvements. Thus, escalation costs are the most suitable term for such a situation.