With the applications of new construction technologies and design ideas, innovative construction methods and architectural designs promote overall productivity and enrich architectural impressions. However, faced with the contradictions between construction efficiency, project benefits, and sustainability, together with the dynamically variable social demands and monotonous design of current temporary light steel structures, a new type of growable light steel structure with parameterisable and assembled architectural units is proposed. Besides, a fast-assembled track foundation that can be detachable and recycled is adopted. Both can promote the growth of light steel units. To be specific, its architectural spaces can be extended and contracted, and the structural form and service space can be adjusted by the reorganisation and optimisation of unit arrangements. Meanwhile, due to the advantages of information integrations and 3D visualisations of BIM technology, a BIM-based design and construction method of growable light steel structures is studied. Based on the arrangements of track and parametrically transformed light steel units, this study expands the architectural forms of light steel structures. It explores their respective applications in practical architectural design to solve current shortages of land resources, properly respond to variable building environments, simultaneously enrich the design schemes of current light steel structures, improve the utilisation rate of structural spaces, and enhance the aesthetic sensations of buildings.