Despite its compact 689-square-foot size, House 64 manages to feel bright and expansive after a recent transformation. The project takes its name from both its 64 square meters of usable space and the 64 years that passed between the building’s construction and the start of OOIIO Architecture’s renovation. What began as a cramped fifth-floor apartment on a modest residential block built in 1960 – one that once tightly housed nine people – has been reimagined by OOIIO Architecture into a vibrant, materially driven home for two.

A woman stands by a dark blue cabinet in a modern, colorful apartment with yellow and orange accents, plants, and contemporary furniture.

Madrid’s Carabanchel district has come a long way since this building marked the edges of the city. Back then, large rural families facing hardships in the Spanish countryside arrived in Madrid looking for stability and a better life. Today that road is buried beneath the adjacent park, the building is served by an elevator, and the neighborhood sits comfortably on the shoulder of central Madrid – a place shaped by global movement. House 64 mirrors this evolution: once dark and subdivided, now bright, fluid, and open to new patterns of life.

Modern living room and dining area with large windows, indoor plants, a blue sofa, round wooden table with chairs, and contemporary decor.

OOIIO approached the renovation as a total reset. The interior was gutted, the tiny rooms cleared to allow natural light to stretch from both facades, which run parallel. Cross-ventilation – a luxury the original residents mostly ignored in favor of pure necessity – now becomes a defining comfort. With the shell stripped bare, the architects layered the apartment like a three-dimensional collage, using color, texture, and carefully curated materials to create new spatial experiences.

A modern living room with a blue sofa, coffee table, plants, a geometric rug, and large window showing city buildings outside.

Modern living space with peach-colored cabinetry, gray seating, large indoor plants, and ample natural light from wide windows.

Instead of fixed spaces, the project relies on strategic insertions that feel both sculptural and purposeful. Each wall becomes a surface to house various materials like art, ones that are reflective, corrugated, tiled, or colorful. These aren’t arbitrary aesthetic choices but the connective elements that form a cohesive space. A white, corrugated metallic plane lives opposite a deep blue sofa; a triangular cabinet beneath it picks up the hue and complements the boxed blue structure by the kitchen. A golden velvet curtain hangs in front of the bedroom for privacy, visually echoing the wall of wavy yellow tiles next to it. In front of the yellow tiles, an olive green sideboard adds a grounded counterpoint, while clay, sky blue, and earthy tones show up throughout in the lamps, counters, and wardrobe finishes.

Modern living room with a corrugated white wall, large potted plants, a black console, books, a geometric art piece, and a pink pendant light.

Modern living room with large potted plants, books, a geometric artwork, glass vases, a pink pendant light, and a reflective coffee table with a drink and books.

A dark cabinet with potted plants and a small stack of books sits in front of a light-colored, textured wall.

A person stands at a modern kitchen island with yellow stools, surrounded by dark and rust-colored cabinets, under pendant lights, with large windows in the background.

A woman stands in a modern kitchen with yellow chairs and pendant light, pouring a drink at the counter near a window.

Modern kitchen with a gray countertop, yellow chairs, pendant lights, glasses, lemons, and plants by a window, featuring dark cabinets and minimalist decor.

Modern kitchen with a gray countertop, built-in sink, yellow accents, wall art, potted plants, and a concrete beam overhead.

A modern kitchen with matte terracotta cabinets, a concrete pillar, glassware, and lemons on a countertop; a blurred person stands in the background.

Furniture is a key component in the design – almost as important as the fixed pieces. Brands like HAY, Kave Home, Cosentino, Grespania, and others in handpicked colors and materials, outfit the rest of the space in an array of fun colors, including pops of sunny yellow, dusty corals, rich blues, making every surface feel intentional.

A person in black clothing opens a tall cabinet in a modern kitchen with matte orange cabinetry and minimalist design.

A modern kitchen with matte pink cabinets, a gray countertop, three blue glasses, a glass decanter with an orange stopper, and two lemons on the counter.

Modern interior hallway with pink built-in cabinets, ribbed beige wall paneling, vertical orange lights, a large potted plant, and a pink pendant lamp.

Modern living and dining area with a blue sectional sofa, colorful cushions, round dining table, indoor plants, and large yellow curtains.

Modern dining area with a round wooden table, four chairs, potted plants, a red sculpture, and a retro sideboard. A yellow slatted divider separates the space from a bedroom.

A decorative tabletop with a geometric jar, four egg holders, potted plants, and wall art against a yellow tiled and red brick background.

A modern interior with a gold curtain partially dividing a bedroom from a living and dining area, featuring plants, wood accents, and soft lighting.

View into a modern bedroom with a blue wall, gray bedding, orange tiled divider, potted plant, books on a wooden shelf, and soft light from a window.

The sleek, box-like structures in blue and coral, not only help define the compact layout, but they add valuable storage throughout the apartment.

A blurred person in black stands near a dark wall in a bedroom with yellow vertical blinds, a curtain, and a framed painting resting on the floor.

A modern bedroom corner with a geometric chair, a floor lamp, a window showing city buildings, and orange-toned lighting.

A modern bedroom features a potted plant on a concrete ledge, dark blue walls, a minimalist pendant light, and a framed artwork visible through a narrow hallway.

A modern bathroom with terrazzo walls and floor, an orange floating vanity, black dual sinks, a potted plant, large mirrors, and a window letting in natural light.

The hues seen in the main living area of House 64, continue into the apartment’s bathroom. The floating sink vanity is finished in the same coral shade as part of the kitchen cabinetry, while blue tones can be seen in the terrazzo surfaces that clad the floors, walls, and shower. Rounding out the space is a black vessel sink and faucet that add a sense of drama.

Modern bathroom with terrazzo walls, a large mirror, black sink and fixtures, and an orange countertop. A rainfall showerhead is reflected in the mirror.

A modern bathroom with a terrazzo wall, a round black vessel sink, matte black faucet, black accessories, and a mirrored cabinet above a coral countertop.

For more information on House 64 by OOIIO Architecture, please visit ooiio.com.

Photography by Javier de Paz.

Caroline Williamson is Editor-in-Chief of Design Milk. She has a BFA in photography from SCAD and can usually be found searching for vintage wares, doing New York Times crossword puzzles in pen, or reworking playlists on Spotify.