When architect Raúl Sánchez first walked onto the site of what would eventually become BSP20 House back in 2013, the existing building was all but in ruins. The floor slabs were damaged, and the existing stairs were already partly demolished. Built in the nineteenth century, the structure of the infill house was far from compliant with current building codes — though it continued to have a striking presence on the street. Raúl Sánchez Architects was tasked with rethinking the building’s four stories, taking into account the relatively modest floor space (barely 80 square metres across all the levels), as well as the client’s evolving family.

From the outside, the BSP20 House’s entrance subtly differentiates itself from the neighbouring houses. An aluminum wall conceals the front door — but it can’t exactly be written off as discrete. Traditional Catalan elements, such as hydraulic tiles, were important aesthetic features of the design, as exemplified by the rhombuses and triangles adorning the garage. This pattern is repeated inside, with the kitchen tile mimicking the house’s lair-like entrance.

To counteract the harsher materials that were used for the original building, Sánchez opted for a warm brass covering in the kitchen — the effect, compounded by natural light shining through the French windows, is that of a lacquered jewel in the rough.

A sleek spiral staircase acts as a point of connection between each floor: the free-standing structure also offers Piranesian views of the interior, depending on where you’re standing in the house. On the opposite wall, window frames are left uncovered and stones unpolished to contrast the softly winding structure.

Glass sheets between each floor provide a vertiginous point of view, reminding inhabitants of the home’s near past — and, in some way, its impermanence. The transparent surfaces also allow natural light to filter in through each floor, brightening an otherwise dark infill building.

The addition of a rooftop patio seems like the cherry on top of a well-constructed sundae — the 4-story building offers generous views of Barcelona’s Borne neighbourhood. Raúl Sánchez Architects’ process resulted in a slowly evolving building in symbiosis with its environment. It may have taken almost a decade, but given the remarkable profile of BSP20 House, not one moment was wasted.