ISO 10848-1 provides a well-established methodology for characterising the vibration reduction index Kij of building junctions. However, its current version does not include specific guidance on configurations involving resilient interlayers, which are commonly used in Cross-Laminated Timber (CLT) constructions. This raises the question of how to reliably apply ISO 10848-1 when a resilient interlayer is present at a CLT junction. This article outlines practical and methodological considerations for this issue, addressing aspects not currently covered by the standard. Through a series of laboratory measurements on two different CLT mock-ups with resilient interlayers, the influence of several parameters was investigated by varying each parameter individually, enabling direct comparison of the resulting changes in Kij. Parasitic airborne noise, the effects of the fastening system (always present in CLT structures), and load effects - already examined in the literature - are briefly discussed. Additional effects specific to resilient interlayers are considered, including the influence of material creep, stiffness, thickness, contact surface area, and the interlayer’s position within the junction. These factors can lead to substantial variations in the measured Kij values, potentially resulting in inaccurate calculations and limiting the comparability between products from different manufacturers.