Buildings in England are heritage listed if they are of special architectural or historical interest, and based on the significance, appropriate conservation priorities can be determined.But to list, and then conserve, one must first identify, then research and assess. The problem is being able to recognise an important example of a semi-detached house (semi) if it is neither very old nor aesthetically appealing. The semi is the most common dwelling type in England, yet because it is typically suburban and ordinary, very little research into its origins and development has been carried out. As a result, semis are under-represented in heritage listings. And once listed, it is difficult, if not impossible, to set priorities for ongoing conservation work or adaptive reuse, without knowledge of the historical or social underpinnings of its significance. Even those ordinary buildings which do not reach the thresholds for listing risk being unnecessarily degraded, through demolition, decay or unsympathetic alterations, if there is no understanding of their stories or meanings, and no safeguards are built into the planning guidelines.