As WUI fires have become a global concern, there is a growing need for engineering methodologies that lead to proactive fire management not only at the landscape level, but at all WUI scales. This paper presents a quantitative methodology for structural vulnerability assessment at the WUI settlement level that is based on 10 indicators, established for the different fire exposure phases a WUI area experiences (pre-impact, impact and fire transfer) as well as on other factors that can escalate vulnerability. As output, a Structural Vulnerability Index (SVI) for the entire analyzed area can be obtained. The methodology can not only assess vulnerability of WUI settlements in a quantitative way, but it can also quantify the effect of measures employed for the reduction of this vulnerability. Additionally, the methodology is suitable for comparison between different settlements or neighborhoods of the same area. A case study for the city of Barcelona, Spain, is presented, in which 9 WUI neighborhoods are analyzed and vulnerability reduction measures are prioritized.