The Fast and continuous technological development has led to enormous amount of waste, the accumulation of waste which is an environmental concern. The demand for natural sand in the construction industry has increased a lot, resulting in the reduction of availability of natural sand resources. Natural sand deposits are being depleted and causing serious threat to environment as well as the society. In this situation research began for inexpensive and easily available alternative material to natural sand, a sincere attempt has been made in choosing waste foundry sand as an alternative & as a partial and full replacement of conventional sand in the Fly ash bricks as well as This paper presents Fly Ash brick properties and comparative study between fly ash brick & clay brick, manufacturing process material required for preparing the fly ash bricks as per Indian standard code provisions, inspection and quality control. The textures of the bricks with Fly Ash were very similar to that of clay bricks; the sample with the additive could have practical Implications as a means of recycling and for achieving cost savings in brick production. The absorption coefficient, shape and size, density, weight, porosity, thermal conductivity and compressive strength of Fly Ash bricks Compare with normal clay bricks that delivered good results. From the present study, it can be concluded that Fly Ash bricks used as an alternative to clay bricks. The strength property are assessed and is compared with the clay bricks and Fly ash bricks. When compared with clay bricks 28 days Compressive strength of fly ash Bricks is 5% more. Water absorption capacity of fly ash brick is less by 0.8% and, Efflorescence for fly ash Bricks is Nil.