Housing for the poor in Thailand in a period of a decade, Baan Mankong Programme (BMP) has been largely focused. This paper focuses on an architectural engineering point of view to explore the housing phenomena with its conversion as well as the usage of extension materials. Extension materials are clarified and made categorizations to unveil the trends of practical urban poor housing case, Bang Bua community in Bangkok, Thailand. Two types of extension were apparent which roof and wall extensions are. The imperative factors to be determined for the extension materials consist of easiness of affordability, easiness of installation, materials cost, durability of usage as well as social situation; safety for instance.