Although the focus remains primarily on high resource efficiency, the significance of flow efficiency in construction is continuously increasing. Flow and resource efficiency describe two competing target viewpoints, which focus on reducing non-value adding activities and maximizing resource utilization, respectively. Recent research has shown that balancing both perspectives provides a viable solution. However, the exact measurement of flow and resource efficiency in construction remains unclear. Therefore, the aim of this work is to evaluate a possible flow and resource efficiency measurement method in the off-site production context of volumetric element construction, and assess the industrial relevance thereof. Work sampling has been used to collect data from a building project flowing through the off-site production system. The validity of the method has been checked statistically, through a focus-group workshop and with calculation figures from the case company. Work sampling allows flow and resource efficiency measurements in an off-site production system. The method delivers current status figures of companies, yielding a balance between flow and resource efficiency.