An environmentally sustainable system must maintain a stable resource base avoiding over-exploitation of non-renewable resource systems. Despite the omnipresence of clay brick and fly ash brick, environmental knowledge about its composition and properties is still scarce. This paper studies the hazards in clay brick and advantages in fly ash brick extending with a comparative study on material properties of clay brick and fly ash brick. The fly ash brick (QFAC brick) used for this study is composed of fly ash, quarry dust, and cement. QFAC brick made of fly ash was found to be an eco-friendly material protecting the environment through conservation of topsoil, reduction in carbon emissions, and utilization of waste products like fly ash and quarry dust. Compressive strength, tensile strength, durability, water absorption, impact resistance, and thermal conductivity of QFAC bricks were investigated and compared with conventional clay bricks. The compressive strength of QFAC brick was 15% higher than that of clay bricks. The flexural strength of QFAC brick was found to be twice that of clay brick. The average water absorption of QFAC brick was as low as 10%. The QFAC brick also possessed high impact resistance and high durability. The thermal conductivity of QFAC brick was as low as that of clay bricks. Hence QFAC bricks are a superior replacement and environmentally sustainable material for clay bricks.