The Macallen Building, the first large project to be completed by Office dA, slopes up to the border of South Boston as a sleek monolith. This enigmatic character may even allude, suggests Nader Tehrani, who directs Office dA with Monica Ponce de Leon, to the Sphinx of ancient Egypt. Given its exposure - a post-industrial site with raised highway and bus garage to the south and multiple railway tracks to the west - and its contents -140 apartments, parking and retail spaces - the building is inevitably monumental. Yet its skin or pelt, adjusting in turn to each exposure, and its incised ridge of private terraces suggest a quality that is almost animalistic. The massing results from the union or hybridisation of two standard forms - row housing and the point tower. From this typological starting-point, Office dA connects lower and higher elements within a cranked, articulate envelope. At one short end of the site, the new monolith has an even parapet six stories high facing Dorchester Avenue, a traditional street in the process of gentrification. The new structure rises, however, and stretches along heavily-trafficked West Fourth Street to a peak fourteen stories high (eleven stories of apartments above three trays of parking). The short lower end and this long inhabited wall together protect a raised communal terrace facing west and north. The observant will notice particular qualities to the skin on all facades. The walls are not of course load-bearing - they are taut membranes made from brick, glass and metal panel. Suspended above the retail spaces, addressing Dorchester Avenue, vertical panels of brick create an elegant checkerboard pattern of positive and negative, the “negative” simulating the scale and appearance of normative window openings. As the bricks are laid vertically, and un-staggered, the smooth panels read almost as decorative shields. The intermittent glazed panes are progressively recessed from this outer brick datum such that light, reflections, and shadow result in a complex, shallow whole. Both flanks of this façade pull away as crisp terminating blades with slender vertical niches. Office dA’s reputation is in part due to its critical exploration of materiality, the way surfaces meet, and the effects generated by surface manipulation. The tallest façade, to the west and soaring above the garage entrance, is dressed in a taut scrim of corrugated aluminium. Pedestrian access is from Macallen Way to the north, into a foyer inlaid with black artificial stone. To either side of the slim entrance canopy, the garage is screened by wafer-like aluminium fins that act as geometric camouflage. The terrace above can be accessed from a splayed, open-air staircase from Dorchester Avenue. This palette of elements is installed within very narrow bands of space, a composite epidermis wrapping the vertical boundaries of the project. Although taut and shallow, both long facades offer clues to the unusual structure organising the bulk of the building. It’s a system of staggered trusses invented by, and named after, the distinguished Boston engineer William LeMessurier. Spanning between the long elevations, the trusses allow for circulation within the building in both longitudinal and transverse directions, for ease of automobile access and apartment layout respectively. Their outer edges are capped by exposed metal covers that give rhythm to the north and south facades. These protruding elements stagger across the walls of taut bronzed aluminium, skipping levels to align vertically every second storey and suggest knuckles or pins in the great metal planes of the façades. The elevations are lined in horizontal strata - reminiscent of film strips or a music score - that corral all fenestration, that are occasionally punctured by recessed terraces, and that also fold back very slightly so that the entire façade appears to ripple in sunlight. The window units shift position within these bands depending on the arrangement of apartments behind. Adding diversity to the exterior, this flexibility in interior planning is indebted to the LeMessurier truss system. The trusses are pierced only by the long central corridor on each floor. Most apartments are single-storey units that can, if desired, be joined laterally. Beneath the angled roof, however, are double- and triple-storey apartments with internal staircases and the splayed rooftop terraces. In two irregular yet spacious units, at the juncture of the monolith along West Fourth Street and the lower segment on Dorchester Avenue, trusses are exposed as walk-through, floor-to-ceiling elements. Office dA liken their general structural concept to a kebab, with apartments free to expand sideways but tethered by plumbing, mechanical and electrical services clustered into vertical ducts. If the practice’s work is characterised by a pragmatic sensuosity, evidenced here by the stone planes and stainless steel screen of the entry foyer, the Macallen Building has also embraced the environmental agenda. In fact it is aiming for a Gold LEED rating (LEED: Leadership in Energy and Environmental Design). This can be partially achieved through the material selection: recycled cotton wall insulation, grass cloth on corridor walls (an individual hue for each level), bamboo flooring, reconstituted macassar ebony or zebra wood veneers, and quartz aggregate work tops. In addition, the patterned sedum roof provides insulation, produces oxygen, and recycles storm water run-off. The roof planting, the communal terrace, and the entry area between the Macallen Building and its neighbour (a former printing press owned by the same developer) were designed in collaboration with Michael Blier of Landworks Studio. The terrace is manipulated horizontally, by a zigzag boardwalk and benches, and vertically, with small mounds of earth pinned by delicate trees. A lap pool in the northwest corner directs the view to Harry Cobb’s seminal John Hancock Tower (1976) and Downtown Boston. At the Macallen Building, the Office dA team has finessed practical concerns and conceptual interests to realise an architecture that is useful, complex, and urban. Raymund Ryan