Munster match.

A small addition to a German atrium house built in the 1960s respects its clear geometries.

Since setting up practice some years ago in the town of MOnster in Germany, Bolles-Wilson & Partners has been quietly contributing a series of vigorous and inventive buildings to that country's architectural scene. Of different types - including a children's day centre in Frankfurt (AR November 1992) and a secular church building (AR October 1993) and library in MOnster (February 1994) - they are each individual responses to quite different contexts, though clearly by the same hand.

If an awareness of context were all, there would be little more to say, but these architects have continually questioned, with some wit, assumptions about how buildings should be put together and function, re-examining building types in striving for intelligent design. It is this quizzical approach that gives their work freshness as well as clear enjoyment in material and colour, and in anecdote. Perfectly at home with the Modern idiom, these architects are able to extemporise, making the language serve their explorations.

The approach informs their design of a small addition to an atrium house in the quiet well-to-do suburbs of Munster. Built in the 1960s in Modern manner and one of several free-standing villas in the area, it is inhabited by a family with two young children. The timber-framed structure around three sides of the atrium encloses a series of free-flowing spaces elegantly conceived in black, white and silver with floors of warm quarry tiles.

The clients asked for the living room to be extended, a small studio and a new fireplace instead of an existing one that was felt to be obstructive.

It seemed important to disturb the elegant composition - the clarity, optimism and simple geometries of the last days of functionalism - as little as possible. Only a small adjustment of the relationship between inside and outside was necessary. Aesthetically, it was felt some horizontal monotony would be relieved by adding another dimension.

The pivot of the new scheme is a new central fireplace, placed between two newly extended spaces pushing very slightly into the courtyard. These can be made one, or can be divided from one another by means of an internal swinging wall. Externally, a new blue glazed brick vertical plane breaks through the line of the existing flat roof. The colour is rich against the cool zinc wall adjoining it and the vertical thrust is balanced by horizontal louvres shading the studio. Such geometric play is continued in the arrangement of slots cut into the flat planes of walls to give doors and windows.

Inside, the architects' pleasure in material and the effects of light are again evident: plywood has been applied severely to form an internal lining in the studio. Flooded by light from the pattern of windows cut into the plane of the external wall, the material is sumptuous against the terracotta floor.