Sustainable Social Housing Architecture: HARQUITECTES’ Innovative Urban Mining Approach in Palma

Introduction to Sustainable Social Housing Architecture

In the heart of Palma, Spain, HARQUITECTES has set remarkable precedent in sustainable social housing architecture with their project, Social Housing Units 2104. Completed in 2024, this innovative residential complex not only provides quality housing primarily for elderly residents but also embodies an ecological and resourceful construction methodology known as urban mining. By repurposing demolition materials from the original site, the architects have seamlessly integrated sustainability, structural innovation, and community-focused design into a single urban intervention.

The Urban Mining Concept in Social Housing Design

The site originally housed a small, disused three-story school built with structural sandstone (marès) walls and concrete-ceramic ceilings, which failed to meet current urban planning standards. Due to its poor condition, demolition was inevitable. However, instead of discarding the old building materials, HARQUITECTES implemented urban mining — harvesting valuable materials directly from the demolished structure to serve as building resources for the new social housing.

This approach transformed demolition rubble into foundational construction elements, exemplifying circular economy principles and drastically reducing material waste and the environmental footprint of the project.

Innovative Material Reuse and Construction Techniques

Following demolition, the rubble was meticulously sorted by material type. Ceramic and concrete fragments, totaling 140 cubic meters, were repurposed and poured into the foundation pits and semi-basement walls. Meanwhile, approximately 160 cubic meters of sandstone were crushed and integrated into the production of around 3,000 large cyclopean concrete blocks.

These prefabricated blocks combined cement, lime, and recycled marès stone, constituting 40% of the block volume. Each block, sizable at approximately 135 cm long and 42 cm high, revealed natural stone faces by cutting slabs with precision saws, enhancing their aesthetic appeal while retaining structural integrity.

Differentiating the structural loads, blocks for upper floors were made of 100% lime concrete, optimizing weight and durability. The lower floors utilized a lime-cement mixture, demonstrating thoughtful material engineering tailored to specific architectural demands.

Structural and Spatial Organization of the Building

The prefabricated blocks were arranged to form load-bearing walls perpendicular to the street, supporting cross-laminated timber ceilings. Wall thickness progressively reduced by 10 cm per floor, allowing direct support of timber panels and speeding up construction.

Inside, 13 cm thick partition walls made from cut cyclopean concrete blocks tied together the building’s structure along with the stair and elevator core. This efficient modular system provided not only strength but also spatial clarity.

The building’s layout centers around a stair core located at the corner, which opens onto a walkway facing an interior garden. Apartments, primarily through-units, are accessed from this communal corridor, with the semi-basement and attic floors featuring shallower depths and double structural spans. Top-floor units boast expansive terraces, while each floor incorporates shared communal spaces such as laundry rooms and lounges, enhancing social interaction and community well-being.

Façade Expression and Environmental Considerations

The building’s façade is a raw and honest display of its structural system. The vertical end walls of the prefabricated block walls, diminishing with each floor, support horizontal timber ceilings. Floor-to-ceiling wooden balconies function as the primary façade element for each apartment, featuring lateral opaque strips and Venetian blinds designed to protect residents from harsh eastern and western sunlight. This combination ensures energy efficiency while maintaining a warm, natural aesthetic.

A Model for Future Sustainable Social Housing

HARQUITECTES’ Social Housing Units 2104 exemplifies how sustainable social housing architecture can respond innovatively to urban challenges. By embracing urban mining and material reuse, the project redefines ecological responsibility within the construction industry, offering a replicable model for future affordable housing initiatives worldwide. The integration of thoughtful spatial planning, structural innovation, and environmental sensitivity positions this development as a landmark achievement in sustainable residential architecture.

All Photographs are works of Adrià Goula