Latest approaches in IT security assessments interpret the Common Vulnerability Scoring System (CVSS) parameters as barriers connected in series. In contrast to the classic multiplicative approach according to CVSS for determining exploitability via numerical values associated with the CVSS parameters, an additive approach is proposed in Braband (2019). Logarithmized CVSS scores are introduced to overcome the computational limitations with ordinal values. The log score sum across all barriers is sorted on a scale corresponding to a likelihood of exploitability (LoE) category. CVSS world is not only decomposed and remodeled into a mathematically admissible algorithm, but it also contains an inherent defense-in-depth (DiD) effect. With each barrier added, the LoE decreases. This architectural interpretation can neither be falsified nor confirmed with previous CVSS metrics. Unlike in the IT security domain, tools exist in physical security to compute DiD in an objectively consistent manner. In our paper, we apply these considerations to a physical security setup in order to replicate his systemic modification based on CVSS. In a detailed analysis, we examine the boundary conditions and measures that must be taken in quantitative physical security metrics to emulate the DiD effect in IT security.