The Emerging “Third Actor” in Architectural Renovation : Roles and Challenges

Architectural renovation in Japan is increasingly supported by self-taught practitioners who are neither professionals nor casual DIYers. This study defines these practitioners as “Third Actors” and examines their practices, roles, and challenges. Based on interviews with eleven Third Actors and Case studies of six renovation projects, including clients and stakeholders, the analysis shows that Third Actors operate under high uncertainty regarding labor, materials, time, and cost. They flexibly combine multiple construction tasks and coordinate with professional craftsmen when required. Through these practices, they complement diverse renovation demands, while challenges remain in construction responsibility, safety, institutional positioning, and long-term continuity.