The design process may be regarded as a compound of two sub-processes performed respectively on internal and external part of a building. Due to different specifics, constraints or standards for both of them, sub-processes are usually carried out separately. The potential problems related to such an approach may arise in areas where both environments share common elements, like windows, external doors, and so on. In the article we overview the mechanism of solving this issue by introducing a coordination between both design sub-processes, namely the external and internal one. Thanks to this an overall consistency of a design is preserved.