The townhouse is arguably the oldest and most ubiquitous building type in much of New York City. Typically, the narrow end facades face the street and rear garden. The simple typology, with its centralized common stair, is remarkably versatile and has served a range of uses from luxury single-family homes to multi-family apartments (occasionally including retail parlor or garden floors), to tenement apartments. In this modern adaptation using a prefabrication system developed by ACHA, a street facing retail space and a garden-facing apartment share the ground floor. Above the ground floor are four floors each with a single bedroom apartment. The common stair extends up to an outdoor roof terrace.