Nestled in the backyard of a Berlin Gründerzeit block, a remarkable compact apartment building designed by Max Hacke and Leonhard Clemens stands as possibly the smallest in Berlin, if not Germany. This prototype addresses the ongoing housing shortage in cities by exploring sustainable development of leftover urban spaces.

To combat the demand for quality living environments amidst stringent financial and regulatory conditions, innovative approaches to inner-city development have become essential. Berlin's transformation into a dense patchwork of urban strategies has necessitated alternative solutions for housing.

The building occupies just 54 square meters (6x9m) and rises seven stories to a height of 22 meters. It features seven small apartments, each with an efficient 38-square-meter floor plan that includes a bathroom, kitchen-living room, bedroom alcove, and a generous south-facing balcony. Extensive glazing invites abundant light while offering views of the tranquil green backyard.

The open-plan design allows for versatile occupancy. Rather than the standard combi oven typically found in Berlin rentals, each apartment includes a durable stainless steel kitchen unit that can easily accommodate standard modules at reasonable costs. This design ensures that kitchens remain visibly functional, contributing to a homely atmosphere even with minimal furnishings.

Developed as an annex to the existing building, this project utilizes the roof of the original structure. A sculptural round staircase, clad in filigree fluted corrugated sheet metal, connects the apartments to the rooftop, which has been extended to feature a communal terrace. This space is accessible to all residents, providing sweeping city views and fostering community interaction.

The spacious roof terrace serves a dual purpose: it is not only an inviting outdoor area but also a clever interpretation of Berlin's building regulations, which require an additional structural escape route via the roof. This design enables the addition of 11 new rental apartments with high architectural standards, enhancing both the living experience and the sense of community among residents.