The global increase in timber usage is generally interpreted as a response to tackle the construction industry's major contribution to greenhouse gas emissions. Meanwhile, there is a growing concern that the expected future demand for timber cannot be met while maintaining sustainable forestry. Efforts to maximize the resource efficiency and service lives of timber products are therefore highly relevant, both to preserve biodiversity and to prolong carbon storage. One such strategy in development is to invest in a timber structure's ability to be locally repaired or adapted to changed user demands - to Design for Structural Adaptation. Yet, stakeholders are uncertain regarding the economic feasibility of such an investment. This study addresses this by investigating which factors are key in determining the economic feasibility of designing for structural adaptation in an Australian multi-residential light-frame timber building. A cost-benefit analysis is performed to compare a structurally adaptable building to a business-as-usual alternative, where the uncertainty of future adaptation needs is considered in the model. The results provide valuable insights for future efforts to implement adaptable timber design, as key aspects for economic feasibility are identified.