Small footprint takes great architectural stride

The urban world is a crowded world and going up does seems the only way forward. But that doesn't mean grey tower blocks reaching for the distant sky. XS House is the story of how two parking spaces turned into seven modern apartments in an intimate, space saving, three-level model that's all about maximisation of space

Designed by ISA

From the architects:

Philadelphia’s urban renewal era left behind an east-west cut through the city’s urban fabric in the form of the sunken, 100-foot-wide Vine Street Expressway.

The Chinatown neighbourhood was one of those disconnected by the expressway, with many of its formerly densely inhabited blocks sliced into odd shapes and sizes.

Today, the expressway continues to divide pedestrian activity, while most of the odd-shaped leftover lots are used for surface parking.

XS House rejuvenates one such leftover site, adding urban density and street life while encouraging walkable lifestyles.

The existing lot chosen for XS House was so marginal and small it was barely noticeable as a development parcel.

But incredibly, the new three storey, 19.2m-high development has placed seven apartments on the 3.3m x 28.3m parcel, expanding the extremely narrow footprint with strategic use of bays, mezzanines, and bi-level upper units while maintaining a minimal single-stair core layout.

This shared stair runs up through the centre of the building with individual unit stairs unlocking mezzanine levels.

Despite the tiny scale of the site, façade projections permitted by the city zoning code were utilised to add up to nearly a metre of width to the horizontal dimension of the building. And the mezzanine levels expanded many interior units by about a third of their floor areas.

Upper units are accessed from the common stair, while lower units enter directly from the street, activating Vine Street with additional foot traffic.

The expanded envelope approach to this project emphasises vertical living.

See the family home by ISA built on similar principles here

Credit list

XS House
Callahan Ward
General contractor
Callahan Ward
Lam Partners
Philadelphia, PA
Project type
Multi-family residential
Structural engineer
Larsen & Landis Structural Engineers

Story by: Trendsideas

Photography by: Sam Oberter

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