Residential building projects, which are one of the main study areas of architecture, have the largest share in the building sector. Demand of housing should be met in a most efficient way especially in our country where housing demand is huge. It is important to designate reasonable design alternatives at the early stages of design process, and this can only make it happen when the decisions are made in a rational way at the design stage. The aim of this study is to investigate the effect of the architectural design of the buildings having the same geometry according to Turkish standards and regulations on the building cost. For this purpose, six housing projects with rectangular shape in plane having various dimensions were designed. These projects produced with tunnel form technology had shear walls as a carrier system and they were examined for 9 different storey numbers. Static analyses of the building models were made with Sta4Cad. It is shown that as the difference between the two dimensions of the horizontal plane increases, the cost of the building also increases in condition that the usage spaces are kept constant. With the increase in height, a U-shape curve, which decreases first to a certain floor and then increases again, is obtained. It is also proved that the projects produced with tunnel form technology are not rational in terms of cost beyond a certain building height. In conclusion, by putting forward the effects of the controlled-variation of the plane dimensions and building heights on the cost of a single building, useful approaches for the designers working for regional planning or urban transformation projects are obtained.