The circular economy transition requires companies to implement innovative supply chains and business models. However, the number of available solutions for the application in the circular built environment is limited. These solutions could be developed through the co-creation between companies aiming for circular transition. However, it is unclear how the co-creation process would look like in the context of the circular build environment. One such case is the REHAB project where stakeholders develop circular building components for housing renovation. Based on the example of one of the components — circular extension — this research develops three process maps of co-creation to help stakeholders organize the co-creation process for the development and implementation of the service loops of the product. This is done by reviewing the academic literature and identifying the requirements and parameters of co-creation for the case for the circular extension, as well as identifying the co-creation designs already available in the literature. Based on this, further process maps were synthesized. The developed process maps consist of six phases: engaging actor, co-conception, co-design, co-production, co-maintenance and co-disposal. Each phase is subdivided into a number of sub-steps for which the best solutions and/or options are mapped. The developed process maps contribute to the circular co-creation literature by showing a clear picture of the co-creation process that practitioners could follow. Additionally, this research evaluates the developed designs with the project stakeholders and derives six lessons learned that could be applicable for circular building components: 1) Cost efficiency is the main aspect influencing implementation of circular building components, 2) Organizing circular co-creation process requires involvement of a human interaction specialist and circular economy consultant, 3) Circularity is largely dependent of the party that initiates the process and becomes the problem owner, 4) Circularity of circular building components in the current reality depends on the formation of secondhand markets, 5) The co-creation process structure is similar for different circular building components, change only network composition and activities/options that could be considered, 6) Sell and buy-back business model and take-back agreements have the most potential for the circular building components, compared to other solution.