A hybrid SWARA-WASPAS approach to enhancing decision-making in adaptive reuse of historic buildings

• Addresses the issue of neglected historic buildings by emphasizing their historical, social, and cultural significance. • Showcases adaptive reuse of historic buildings (ARHB) as a sustainable practice to maintain heritage value. • Introduces a new decision-making tool combining SWARA and WASPAS to address complexity and subjectivity in existing methods. • Applies the methodology for a case study in Sri Lanka, identified "Adaptive Reuse for Homestay" as the optimal solution. • Provides a practical, simplified tool for early-stage ARHB project evaluation, supporting balanced decisions across social, economic, and environmental pillars. Adaptive reuse of historic buildings (ARHB) is increasingly recognized as a critical strategy for reducing embodied carbon loss while preserving cultural identity. However, decision-making for ARHB remains constrained by complex and subjective evaluation frameworks and by the limited transferability of models developed primarily for temperate climates. These limitations are particularly pronounced in warm-humid tropical contexts of the Global South, where climate-responsive factors such as Indoor Environmental Quality (IEQ) are essential yet frequently underrepresented. This study develops a transparent, context-adapted Sustainability Index (SI) and Decision Support Tool (DST) tailored to tropical heritage buildings. A hybrid Stepwise Weight Assessment Ratio Analysis (SWARA)–Weighted Aggregated Sum Product Assessment (WASPAS) framework is employed to balance analytical rigor with interpretability, reducing cognitive burden while maintaining decision transparency. Evaluation criteria were derived through statistical screening of technical parameters and synthesis of heritage literature, explicitly incorporating locally relevant drivers including IEQ and Socio-Cultural-Historic (SCH) value. The framework was applied to a 17th-century residential building within the Galle Fort World Heritage Site, Sri Lanka. Results identified SCH as the dominant sustainability criterion, confirming the need for heritage-centered decision priorities in adaptive reuse. Adaptive reuse for homestay (A3) emerged as the optimal alternative (A3 > A4 > A1 > A2), achieving the best balance across environmental, economic, and socio-cultural dimensions. External validation demonstrated strong agreement with expert judgment (Kendall’s W = 0.712; Spearman’s ρ = 0.80), confirming the robustness and stability of the proposed approach. The validated DST provides practitioners and policymakers with a reliable, low-subjectivity, and climate-responsive tool to support evidence-based adaptive reuse decisions for historic buildings in resource-constrained tropical contexts across the Global South.