Multi-unit housing on narrow urban sites forces architects to reconcile density with livability. A typical site measuring less than 10 meters in width leaves little room for conventional layouts, yet the demand for housing in dense city centers continues to push development onto these constrained parcels. The VOID+ project in Tehran demonstrates how a carved opening through the building mass can transform a tight site into a series of well-lit, spatially generous dwellings. The small studio architecture design strategies applied in compact projects offer parallels for making efficient use of limited footprints while maintaining a high standard of interior quality.
The Urban Density Challenge and Its Impact on Building Design
Tehran experienced rapid transformation over four decades, shifting from a city of single-family homes with gardens to one dominated by apartment blocks. This density-driven construction process, focused almost entirely on economic returns, produced closed building envelopes that lack visual or spatial connection to their surroundings. Buildings turned inward, streets became corridors of blank walls, and residents lost the visual relief of varied facades and planted frontages.
Architects working on narrow urban infill sites must address three specific issues that do not arise on wider parcels. First, daylight penetration drops sharply as floor plates become deeper relative to the street frontage. A room that is 12 meters deep from the window wall receives less than 2 percent of exterior daylight at its far end, which makes deep-plan apartments reliant on electric lighting for most of the day. Second, cross-ventilation becomes difficult when one side of the building faces a wall or neighboring structure. Third, the relationship between the building and the street is compressed, making it hard to create a welcoming entrance that feels neither cramped nor exposed. The soundproofing and noise control techniques developed for custom-built studios provide a useful reference for the acoustic separation needed between units in these dense configurations where party walls and shared structural elements are unavoidable.
The Void as a Spatial Strategy for Site Engagement
The defining feature of the VOID+ project is an opening carved into the north facade that extends the full height of the building. This void does more than provide light and air to the interior units. It creates a vertical spatial link between the roof and the ground, drawing the skyline down into the pedestrian experience and pulling the street level up through the building mass.
| Void Function | Design Implementation | Effect on Building Performance |
|---|---|---|
| Vertical connection | Full-height opening aligned with north facade | Links roof skyline to ground level, draws natural light into deep floor plates |
| Horizontal platform | 20-meter span at entrance level | Extends street into garden, defines building territory without walls |
| Facade articulation | Carved massing creates varied depths | Breaks down building volume, reduces visual dominance on narrow street |
| Interior-exterior transition | Void surfaces open to adjacent rooms | Provides borrowed light and cross-ventilation for units on both sides |
The massing of the void creates a vertical flow that changes character from floor to floor. At the main entrance, the vertical cavity turns into a horizontal plain extending 20 meters along the length of the building. This platform connects the street to the back garden and redefines the building’s territory without rigid borders. The approach shares design principles seen in the log yoga studio in Michigan, where an opening through the building volume becomes the organizing device around which all other spaces arrange themselves.
Unit Layout and Circulation in Narrow Multi-Story Buildings
VOID+ consists of ten units spread across five floors, an average of two units per level. The narrow site width forces the architect to stack dwellings vertically rather than spreading them horizontally, which changes how circulation, services, and room proportions are designed. Corridors must be kept to a minimum because every square meter of hallway reduces the usable floor area of the units. In conventional apartment buildings, circulation consumes 15 to 20 percent of the total floor area. On a narrow site, that figure must drop below 10 percent to keep units large enough for comfortable living.
Vertical Circulation Core
A central stair and elevator core serves all five floors. The stair is positioned to receive natural light from the void, turning the vertical circulation path into a light-filled experience rather than a dark enclosed shaft. This strategy improves wayfinding and reduces the need for artificial lighting during daytime hours. The landing at each floor opens onto the void space, creating a visual connection between levels that helps residents orient themselves within the building.
Unit Proportions and Room Depth
Each unit in VOID+ has a ratio of depth to width that would be considered extreme in a conventional apartment building. Rooms extend up to 12 meters from the facade face, which would normally result in dark interiors at the back of each room. The void solves this by providing a second light source on the north side of each unit, so rooms on both the street and garden sides receive borrowed light and ventilation across the full depth of the floor plate. Sliding partitions between living and sleeping zones allow residents to adjust their floor plan throughout the day, opening up for cross-ventilation in the afternoon and closing for privacy at night. The efficient guest house layouts developed for compact sites demonstrate a similar approach to maximizing usable space within constrained proportions.
Connecting Interiors to the Street and Garden
The horizontal platform at ground level does not simply serve as an entrance. It extends the building’s interior territory into the landscape, dissolving the hard boundary between private dwelling and public street. The 20-meter horizontal surface connects the front sidewalk to the rear garden and allows residents to experience the full depth of the site as a continuous outdoor room.
This strategy challenges the conventional approach to multi-unit housing where each unit isolates itself behind a front door and a set of curtains. Instead, the building opens up at ground level to offer shared outdoor space that feels like an extension of the individual dwellings. Each unit above the ground floor benefits from the void’s ability to draw garden views upward. Residents on upper floors can see greenery from their windows even though the garden sits two or three stories below them. The same principle of extending interior function into adjacent spaces appears in strategies for creating a dedicated studio space at home, where the boundary between work and living areas is softened by careful spatial planning and shared volumes.
| Connection Type | VOID+ Solution | Benefit to Residents |
|---|---|---|
| Street to entrance | 20-meter horizontal platform | Gradual transition from public sidewalk to private entry |
| Ground to garden | Platform extends to rear garden | Shared outdoor space visible and accessible from lobby |
| Lower to upper floors | Full-height vertical void | Garden views reach upper units, borrowed light for deep plans |
| Unit to unit visually | Void surfaces face each other | Sense of community through shared vertical space |
Noise Control and Privacy Between Dwelling Units
Placing ten units on a narrow site raises the risk of noise transfer between dwellings. Party walls between adjacent units must achieve sound transmission class ratings of STC 50 or higher to prevent conversational speech from carrying between apartments. The void presents an additional acoustic consideration: sound can reflect off the facade surfaces and travel upward into upper-floor windows, bypassing the party wall isolation entirely.
Architects can address these issues through a combination of strategies. Offset window placements across the void prevent direct line-of-sight and reduce the acoustic path between facing units. Absorptive surfaces within the void cavity reduce flutter echoes. Sealed glazing units with laminated glass on interior-facing windows provide STC ratings comparable to exterior walls. Floor-ceiling assemblies between stacked units require resilient channels or acoustic underlayment to meet code minimums for impact noise isolation, typically IIC 50 in most jurisdictions. The soundproofing techniques used in home music studio construction offer practical approaches that translate directly to the acoustic challenges of multi-unit housing, including resilient channel mounting, mass-loaded vinyl barriers in partition assemblies, and double-stud wall construction where space allows.
Adaptive Approaches for Existing Urban Fabric
The VOID+ project sits on a site that was carved out of the existing urban block, surrounded by neighboring buildings on three sides. This is a common condition in older city neighborhoods where development happened incrementally rather than through master-planned lots. Architects working on these sites must accept the asymmetry of adjacent buildings and design around the irregular boundaries they create.
The void strategy proves particularly effective in this context because it brings light and air into the center of the site rather than relying on perimeter windows that might face a neighboring wall two meters away. Interior rooms in the units receive daylight reflected off the void surfaces rather than direct sky exposure, which produces a softer, more even illumination that suits living spaces well. The entrance platform and the rear garden connection give the building what looks and feels like a single-family house footprint despite containing ten separate residences. For similar transformations of existing structures, the approach to converting a barn into an exercise studio and office shows how adapting existing volumes to new uses can produce spaces that retain the character of their original fabric while serving entirely different programs.