Steel arbour: a tautly detailed steel pergola forms the formal and spatial focus of a new Korean restaurant in downtown Los Angeles.

Richard Lundquist trained at the AA and acquired his mastery of steel working for Morphosis in the mid-1980s and then for Michele Saee, where he was project designer on two cuttingedge clothing stores. His most ambitious project since setting up his own office in 1990 is the Chosun Galbi restaurant in Koreatown, a burgeoning immigrant community west of downtown Los Angeles. For the client it represented a big step up both in size (790 sq m) and sophistication from her other restaurant a block away, and a daring departure from the traditional red and gilt of the neighbourhood eateries.

The corner site faces onto a busy commercial thoroughfare and was occupied by a brick building that Lundquist was commissioned to remodel and extend. When it proved to be unsafe and was torn down, the architect designed a layered steel and concrete structure within the original footprint, so avoiding the need for a new permit. An almost unbroken wall of split-face concrete block wraps around the two street facades, shutting out traffic noise. Nearly everyone enters from the rear car park, and Lundquist has choreographed a succession of eating and circulation spaces that subtly blur the boundary between indoors and outdoors.

You enter between 3m-high block walls past an eye-level water garden, under a muscular steel pergola and between a pair of semi-enclosed banquet rooms to reach the bar and reception area. The main dining room opens off to the left; ahead is an intimate eating area, screened by a high-backed bamboo bench. At the front, looking north through high narrow windows, is a long room that can be subdivided by pull-down mesh blinds to create three spaces for private parties. In its fragmentation, the restaurant responds to an East Asian fondness for gatherings of family or friends, but the transparency and honed slate floor that extends through from car park to street line ties these intimate areas together.

Materiality and bold sculptural forms are the design's hallmarks. The pergola has become the restaurant's signature. Rolled I-beams support four shallow interwoven arches, each comprising a pair of rolled I-beams spanned by a trellis of vertical steel slats that will be covered with bougainvillaea. The structure was fabricated off-site and delivered in 13m sections that were hoisted into place by crane. Two banquet rooms, separated by a circulation area, have arched vaults of bamboo boards interwoven like the strands of a basket within a stainless-wrapped steel frame.

Walls of the same boards are cut away at top and bottom to admit air and natural light. Built-in seats are stained and upholstered plywood on a stainless-steel frame. Aluminium-plate patio chairs have waterproof foam lining. The spacious entry area has a bamboo reception desk facing a bar and both have tops of curved aluminium plate. Tabletop barbecues are the restaurant's speciality and stainless exhaust vents reach down over every grill, giving the main dining area a somewhat menacing air.