Minimal Intervention and Adaptive Reuse in Small Urban Apartment Design

Designing a full apartment for one person on a limited budget requires architects to abandon conventional approaches and look for efficiencies in existing conditions. The House in a Corridor project in Quito, Ecuador, shows how two simple strategies: limiting intervention to what is strictly necessary and allocating budget to materials rather than complex construction, can produce a functional home of only 54 square meters. The project occupies the front facade of a second-floor apartment, facing the street through two previously unused terraces and an exterior corridor. By relocating a single window and concentrating all new plumbing and electrical work into a 1.24-meter-wide strip, the design team transformed an underutilized corridor into a full kitchen while preserving the existing floor finishes and fixed furniture. This approach aligns with passive house design principles for warm climates, where the first move is always to work with the existing building fabric rather than replace it.

Minimal Intervention as a Design Strategy for Constrained Budgets

The minimal intervention approach rests on a single premise: every square meter that does not get rebuilt is a square meter that does not need to be paid for. In renovation projects, demolition and reconstruction costs typically range from $30 to $80 per square foot depending on the extent of structural changes, finishes, and MEP work. By limiting intervention to only the areas that must change to meet the program requirements, architects can deliver functional spaces at a fraction of the typical renovation cost. The Quito project achieved this by drawing a hard boundary around the work zone. The existing study, guest room, and circulation spaces remained untouched. Their carpet floors, paint, and fixed furniture stayed in place. The only interventions in these rooms were the addition of furniture, not construction.

The critical design decision involved moving the strip window of the existing guest room toward the edge of the exterior corridor, creating a narrow slot barely 1.24 meters wide where the new kitchen would go. Concentrating all electrical and water supply lines within this single narrow space meant the rest of the apartment required no new MEP work. Growth corridor development strategies in residential construction follow a similar logic: concentrating infrastructure in a defined band to minimize disruption to existing spaces while maximizing functional output within the intervention zone.

This selective approach requires rigorous pre-design documentation. The architects verified that existing floor finishes, wall conditions, and furniture could meet the new program requirements before committing to the preservation strategy. Any hidden condition, such as moisture damage or structural sagging, discovered after the design freeze would force a scope expansion that the budget could not absorb. The solution was a thorough pre-construction survey that tested every surface scheduled for preservation, including moisture meter readings and structural assessment of the corridor floor framing where the new kitchen loads would be placed.

Narrow-Space Kitchen Design within a 1.24-Meter Corridor

Designing a functional kitchen within a corridor only 1.24 meters wide presents ergonomic and code compliance challenges that most kitchen designs never encounter. Standard kitchen base cabinets are 60 centimeters deep, leaving a passage width of 64 centimeters, barely wider than a standard doorway. The design team addressed this by building all kitchen elements into a single wall, keeping the opposite corridor wall clear for circulation. This single-wall kitchen layout, sometimes called a pullman kitchen, places every appliance, storage unit, and work surface along one linear plane so the cook can reach everything without crossing the circulation path.

Space-Saving Features in the Corridor Kitchen

The narrow width dictated several specific design choices:

• Counter depth reduced to 50 centimeters instead of the standard 60, saving 10 centimeters of passage width while still accommodating standard under-counter appliances
• Full-height upper cabinets reaching the ceiling to maximize storage, with pull-down shelving for access to upper items
• Compact under-counter refrigerator (76 cm wide), two-burner induction cooktop, and a slim dishwasher (45 cm wide)
• A protruding wooden module at the corridor exit that serves triple duty as storage, sink base, and window seat, extending beyond the corridor line where the space opens to the terrace
• Natural cross-ventilation from the corridor window to the terrace, eliminating the need for a mechanical range hood

The Protruding Wooden Module

The protruding wooden module at the corridor exit is the most innovative element of the kitchen design. By cantilevering 40 centimeters past the corridor wall line into the terrace opening, the module captures space that would otherwise be dead circulation area. This module houses the sink base, provides countertop prep space outside the narrow corridor, and creates a window-side spot for casual dining. The wastewater pipes from the sink pass through the module’s base and exit to the terrace below, where they feed into the natural water purification system.

Self-Construction and Community Participation in Urban Projects

The Quito project relied on mingas, a traditional Andean practice of community work parties where neighbors and friends contribute labor to a shared project. In the context of a small urban apartment renovation, the minga model allowed the owner to direct the limited construction budget entirely toward materials rather than paying for skilled labor. The concept of designing eco-resort communities with natural materials and bio-corridor planning shares this emphasis on community participation as both a cost-saving mechanism and a social benefit, where building together strengthens relationships among the people who will use the space.

The work completed through mingas included demolition of the existing window opening, surface preparation for the new kitchen finishes, painting, furniture assembly, and installation of the terrace composting and water purification systems. Work requiring licensed professionals included electrical wiring, plumbing connections, and structural modifications to the corridor floor. The owner coordinated the minga schedule, sourcing volunteers from among friends, family, and neighbors who had construction experience or were willing to learn on the job. The architect provided detailed construction drawings that a non-professional could interpret, with step-by-step installation sequences for each assembly.

One risk of self-construction is inconsistent quality. The project mitigated this by limiting volunteer work to non-structural, non-waterproofing tasks where minor variations in workmanship would not affect building performance. Critical enclosure details such as window installation, roof flashing at the corridor wall, and waterproofing around the kitchen sink were performed by professionals. This segregation of work by risk level is a replicable strategy for any project mixing professional and volunteer labor.

Flexible Room Configurations for Multi-Purpose Living

A 54-square-meter apartment cannot afford single-purpose rooms. Every space in the Quito apartment must serve multiple functions, and the design achieves this through furniture strategy rather than construction. The study doubles as the master bedroom, with a sofa bed or floor futon that converts the space from work to sleep mode. The guest room transforms into a living-dining room and study, with a retractable bed stored in a cabinet that disappears when not in use. The retractable bed cabinet is the hardest-working piece. When closed, it reads as a wall of storage with a desktop surface that folds down to create a study area. When opened, the bed pulls out on casters and the desktop folds up to clear the floor.

The relationship between these two flexible rooms is mediated by a slight level change at the corridor. The kitchen sits 15 centimeters lower than the study and guest room, creating a subtle threshold between the cooking zone and the living zones without building a wall. This level change means the study and guest room share visual and acoustic connection through the open corridor even when both are occupied for different activities. Modern barnhouse design concepts use similar level-change strategies to differentiate functional zones within open floor plans, showing that subtle elevation shifts can replace walls as space dividers.

The apartment is separated from the main house by a diagonal dry-built wall: a framed partition with gypsum board that does not require wet trades and can be dismantled without damaging existing finishes. The diagonal orientation was chosen not for aesthetic reasons but to maximize clear floor area in the apartment while preserving circulation space in the main house corridor.

On-Site Natural Water Purification Systems for Urban Apartments

One of the most distinctive features of the Quito apartment is the water purification system that treats wastewater from the kitchen sink. Rather than connecting to the municipal sewer system, the kitchen wastewater flows through a series of natural filters before being used for irrigation. The system begins with the sink drainpipe, which exits through the protruding wooden module and drops to the terrace below. From there, the water enters a constructed wetland: a shallow basin planted with aquatic vegetation that removes organic matter and nutrients through biological uptake and microbial activity in the root zone.

The purification sequence operates as follows:

• Wastewater from the sink enters a primary settling tank where solids settle out
• Liquid flows through a gravel bed planted with reeds and aquatic plants that filter and biologically treat the water
• Treated water collects in a small reservoir and is used for irrigating fruit trees, ornamental plants, and the home composting system
• Overflow is directed to a percolation area within the terrace planters

For an apartment with limited outdoor space, the system had to be compact. The entire constructed wetland fits within a 2.5 by 1.5 meter planter on the terrace, with a depth of 60 centimeters. The system was built primarily by the owner and neighbors through the minga process, with the only contracted work being the waterproof membrane that lines the planter. Window selection strategies for the apartment prioritized operable awning windows at the corridor, allowing the owner to control ventilation rates that complement the natural water treatment cycle by managing humidity levels near the planters.

The lower terrace remains as free outdoor space, available for the client to use for yoga classes or other activities. This dual use of the terrace, part natural water treatment and part community gathering space, mirrors the apartment’s overall design philosophy: each element serves multiple purposes, and the boundaries between infrastructure and living space are deliberately blurred. The combination of natural filtration, composting, and edible landscaping creates a closed-loop system where kitchen wastewater irrigates the fruit trees and ornamental plants that, in turn, provide food and a pleasant environment for the occupant. Projects like the Quito corridor house show how showcase home design principles can translate into real-world urban applications where tight budgets and confined spaces demand every square meter to earn its keep through overlapping functions and material efficiency.