The intention of this paper is to provide a comparative parametric approach that to analyze informal housing patterns and to develop alternative housing paradigms by designing new formal housing patterns in Istanbul. This paper focuses on parameters which are effective in the formation of “informal housing settlements” considering the formal housing production alternatives. Observation, actual sources and parametric evaluation was used. This study aims to make comparison between organic informal housing structure and formal housing structure in Maltepe/ Istanbul housing settlement and analyse their physical and spatial patterns by using parametric evaluation approach.