Baltic exchange.

With the reunification of Germany, the port of Barth on the Baltic coast near Rostock has lost its industrial role, with the harbour serving increasingly as a marina. Its industrial buildings - granaries and a fish factory - had become redundant, and developers from Kiel decided to turn one of them into an apartment hotel.

Giencke has transformed the appearance and identity of the building, yet kept the memory of its former function by respecting and preserving the most telling aspects of the structure.

The building, composed of two almost equal parts, stands at the corner of the old harbour facing west across the water. The north end was a series of open storage floors supported by a cast iron column and beam system giving bays approximately four metres square. This was simple to convert, and has become a series of large flats.

The other end of the building presented more difficulty, for it consisted of a series of 12m-high storage silos only 3m wide.

These consisted of timber constructions inside the brick outer casing, descending to the inverted pyramids of hoppers which delivered grain to an open loading floor beneath. Giencke kept the whole arrangement, devising a series of narrow apartment types to fit. There are some single rooms and some paired rooms made by piercing holes from one silo into the next, but most of the space is given to two-storey apartments with a small entry room on one level and the whole width of the building on the next, rather like the scissor plan of flats in Le Corbusier's Unites. Both in the silo apartments, and in the larger ones occupying the north end of the building, the bathrooms are wet cells: complete boxes, uncompromisingly new.

The old windows were short and narrow under modest brick arches. One set remains, lighting the old stair on the middle of the south side. As they were inadequate, Giencke decided to enlarge them in the least disruptive way: by extending them vertically to the floor.

There were no existing windows in the silo part of the building, so new ones had to be cut on both sides and in the south end. These take the same form and dimension as the others, but because of the hoppers and the new floor arrangements, they occur at different levels. Giencke shows that they are new by incorporating steel lintels. Appropriately, the basement contains a visitable wine cellar, sauna and gym as well as service facilities. The ground floor is all bar and restaurant, the silo hoppers and their structure providing an impressive ceiling in the latter. Glass panels are let into the floor around the cast-iron columns to reveal the continuity of the structure.

On the harbour side, Giencke added a slender extension which starts as entry ramp and ends as a glazed extension for the bar. The canopy is insubstantial plywood and canvas, with a supporting structure of tubular steel. Cleverly, this is not vertical, but takes a self-bracing zigzag form, so its rhythm remains independent of the old work. The existing double-pitched roof was in very poor condition and had acted merely as a hat for industrial functions. Having removed it, Giencke added two fiat slabs with balcony and glazing between, leaving a deep shadow gap between the lower slab and the old eaves-line. The brick infill of the old top floor was replaced by glazed panels and the rhythm of the structure stressed by exposing the brick piers.

In planning the topmost floors, it was possible to break with the tighter bay arrangement demanded by the silos. Instead, the promise implied by the brickwork of 10 equal bays across the whole building was finally fulfilled. The top apartments are all maisonettes with spiral stairs, and the shared balcony of the upper level doubles as fire-escape. Compositionally, it was of the utmost importance that the full-height glazing was pulled back from the perimeter, for thereby the top storey is detached visually from the rest of the building and its own flat cap can be read as a roof element. The underside is visible, so it is not just the top surface of a cube. Notionally, the roof is made no less than three times: first by the old eaves, then by the balcony layer and finally by the top slab. This drastic unusual treatment succeeds very well in giving the building an open, festive air as opposed to its former dour and functional appearance.