Plastic lumber, produced from virgin or recycled plastics, offers a sustainable alternative to lightweight structural wood materials. Utilizing recycled plastic as a construction material helps reduce plastic waste sent to landfills and incinerators. Cold-formed steel (CFS) is commonly used in manufacturing lightweight structural elements, and both materials can be combined to create cost-effective lightweight building components compared to traditional materials. This study focuses on plastic lumber beams made up of PVC material externally reinforced with CFS encasement, aiming to develop a sustainable, fire-resistant composite beam made from recycled plastic lumber blocks strengthened with CFS. The research investigates the strength characteristics of plastic lumber beams and CFS encased plastic beams, with and without fire-resistant materials. Various layers of fire-resistant coatings using intumescent and silicon resin based spray paint are analysed. Key parameters such as ultimate load, ultimate displacement, and failure patterns are evaluated using a Universal Testing Machine (UTM). The findings optimize the performance of fire-protected plastic lumber beams and CFS-encased plastic lumber beams under the temperature exposure by comparing them to normal unprotected beams. Ultimately, this paper introduces an innovative, lightweight, fire-resistant composite beam designed for short-span applications.