Lean construction based process improvement model for companies in the turkish timber housing sector

Eliminating process waste and boosting productivity in construction has been a global challenge for years. The sector's labor-intensive nature and a decline in professional skills have been identified as major factors limiting productivity gains. Research shows that adopting offsite construction (OFC) methods, which use prefabrication, offers a promising solution to these challenges. In OFC, parts of the structure are manufactured under controlled conditions offsite, yielding notable benefits in quality, safety, cost, time, sustainability, and productivity. Due to these advantages, OFC is widely recommended for efficient wooden house construction and is prevalent in low-rise housing in countries like Sweden, the USA, the UK, and Japan. To improve productivity in Turkey's wooden housing sector, it is important to increase the offsite production rates and efficiency in construction. Preliminary interviews with Turkish companies using high levels of OFC for wooden houses revealed persistent process inefficiencies despite their adoption of these methods. However, none of the companies utilized scientific tools or methods to analyze and improve their construction processes. This highlighted a need for a customized process improvement model to enhance productivity, reduce inefficiencies, and foster sector-wide growth. The primary goal of this thesis is to develop a lean construction-based process improvement model for Turkish wooden house manufacturers employing OFC methods. The secondary goal is to identify common inefficiencies in the construction processes of these companies, and the third is to provide an overview of OFC practices within Turkey's wooden housing sector. This research included a literature review on wooden housing construction systems and wooden housing sectors in Türkiye and World. Relevant studies and models aimed at improving wooden housing production were examined, revealing that "Lean Construction" is a widely applied approach internationally in this field. So it was decided to include it in the conceptual basis of the research with the idea that it would provide a driving effect for Turkish wooden housing companies as a process improvement approach. Following the literature review, preliminary interviews with Turkish companies helped identify current practices and challenges in the sector. Based on these findings and literature insights, a draft lean construction model was developed, which was then refined through in-depth interviews to ensure practical applicability. The study identified several forms of waste in construction processes, including faulty designs, manufacturing errors, rework, delays, extra processing, and unnecessary transportation, leading to wasted labor, time, and money. Despite these losses, companies lacked scientific tools for detailed waste analysis at each construction stage, leaving many issues and root causes undiagnosed. To address this, a lean construction-based process improvement model was proposed to identify, analyze, and minimize waste in construction processes. Tailored to the sector's needs, the model outlines steps for selecting the process to examine, gathering data, identifying and analyzing waste, and recommending improvements. Following these steps allows companies to pinpoint the root causes of waste and develop targeted process improvements. A case study demonstrated the model's effectiveness by quantitatively identifying waste across all main and sub-processes, revealing their root causes, and outlining actionable steps for waste reduction. The Turkish timber housing sector requires simple, cost-effective solutions, and this model provides a valuable framework for identifying and improving process inefficiencies. Additionally, this study aims to serve as a resource for future research in this field. Keywords: Timber Construction Systems, Timber Housing Sector, Offsite Construction, Lean Construction, Process Improvement