End-of-life and Beyond Building Life: Carbon Benefits of a Novel Mass Timber Wood Floor System, Evaluating End-of-Life Strategies, Recovery Rates, and Circular Design Implications

Abstract Purpose Mass timber construction is gaining attention as a low-carbon alternative to conventional building systems, but the end-of-life (EOL) stage remains one of the least consistently modeled phases in building life cycle assessments (LCAs). This study evaluates how recovery pathways and connection strategies influence the climate performance of prefabricated hollow timber floor systems. Methods A process-based estimation approach was used to quantify the carbon footprint of two timber floor systems—Adhesive & Screw and Sharp Plate & Screw—following ISO 14040/44 standards. Four realistic EOL pathways (landfilling, downcycling, component reuse, and full assembly reuse) were assessed under three recovery-rate scenarios (90%, 60%, and 30%) to capture both ideal deconstruction and conventional demolition conditions. Cradle-to-gate impacts, biogenic carbon flows, and Stage D benefits were integrated to determine climate outcomes. Results Results show that reuse, particularly modular assembly salvage, delivers the highest climate benefit, achieving net-negative emissions and offsetting cradle-to-gate greenhouse gas impacts. Mechanical fastening systems (sharp plate and screw design) outperformed adhesive-based designs in both reuse effectiveness and environmental impact compensation (Stage D), emphasizing the importance of disassembly-friendly connections. However, downcycling benefits diminish sharply below 60% recovery, highlighting critical thresholds for climate performance. Furthermore, break-even recovery thresholds were identified: downcycling becomes environmentally favorable only when recovery exceeds 59%. In contrast, component reuse is beneficial from 15% recovery, and assembly reuse from as low as 10%. These thresholds reinforce the strategic advantage of designing for reuse, not just recycling. Conclusions The findings highlight the strategic advantage of designing for reuse rather than recycling, with disassembly-friendly connections and high recovery rates emerging as key enablers of climate-positive outcomes. This study provides new methodological and practical insights for incorporating EOL pathways into timber building LCAs and supports circular economy strategies in construction.