The economic focus in the building sector is on lightweight materials. Recycled polyethylene particles coming from plastic botteles waste can ensure this lightness and can solve not only technical problems, but also produce economic and environmental benefits. Different polyethylene particle proportions of 5,10,15,20 and 25% were introduced in gypsum mortar in order to characterize its physical and mechanical properties. Results proved the positive effect of the introducing of PET particles in the matrix of gypsum mortar, the lightening of this material but a decrease of mechanical properties was recorded comparing in to reference without polyethylene particles. This new material with promising functional properties can be used as a masonry element in a new construction or in the rehabilitation of the old building.