The construction sector has suffered from low productivity and considerable waste due to the fragmentation of its value chain and inefficient design and material usage processes. The circular economy (CE) principles have gained significant attention among researchers and practitioners to help overcome these challenges. Construction materials such as timber and steel elements will lend themselves more easily to reuse and recycle for new construction to reduce carbon emissions. The BIM-based LCA method could be explored and expanded to evaluate design options for circular construction to advance the knowledge about implementing circular economy principles in construction projects. However, this is relatively new and requires proof of concepts to demonstrate precisely how BIM-based LCA could be implemented to help stakeholders decide on optimal design options and material choices. To address this need, this study proposes a BIM-based LCA process for comparing the carbon impact of two design model options considering different material choices, including the possibilities of using virgin materials and recycled and reused materials. Findings show that the timber structure was favored over the precast concrete structure because timber materials entailed less carbon emission; however, the precast concrete structure has great potential of being reused for future new construction projects. Findings also show that Module A (with timber and steel materials) has a slightly higher circularity (39%) than Module B (with concrete materials) with 37% circularity.