Although the terms "expressionism" and "Amsterdam School" are often used in the same meaning, there are a few differences. But it is true that the Amsterdam School is the most important of the different expressionistic styles, and most of the others were influenced by it. This page is a short introduction. A seperate page handles with expressionistic religious architecture.
The Amsterdamse School, as it is known in Dutch, originally was the name for a style developed shortly after 1910 by architects M. de Klerk (1884-1923), J. van der Mey (1878-1949) and P.L. Kramer (1881-1961), who all previously worked at Ed. Cuypers architects office in Amsterdam. Their style was characterized by organic shapes and purely decorative structures such as towers. Buildings in this style had a concrete skeleton covered with a brick layer that could take the most imaginative shapes, as if they had been sculpted. Sculpting in clay was in fact often one of the first stages in designing a new building. Whether it was practical or not, the interior of a building was adapted to fit the outside shape. Building materials were often used in a way they were not intended for; roofing tiles covered vertical surfaces, and bricks were often laid vertically, both purely for decorative purposes. Windows, which had sometimes odd shapes, like the inverted parabola, were often divided in several smaller ones, and held in thick wooden window-frames, which were usually painted white for optimal contrast with the dark coloured brickwork. There was intensive cooperation with a group of sculpters, who supplied sculptures to decorate the buildings. The best examples of this style can be found in Amsterdam, especially in the neighbourhoods directly to the South of the centre, which were build to accomodate thousands of factory-workers who previously had to live in slum dwellings. In the same city this style became the official one for local institutions, like bridges, post-offices, schools etc.. Other architects followed the example, and often developed their own variants. After 1925 cuts in budgets forced the development of more simplified variants, which accounted for more straightforward shapes and little to no use of sculpture. By 1930 the style had almost disappeared. Internationally it was of little influence, except perhaps for the border regions of Belgium, and it's only quite recently that the style has been reappreciated.
The picture above shows a classic example of Amsterdam School architecture, Het Schip by Michel de Klerk. Notice the curved facade, the use of roofing tiles to cover vertical surfaces, the thick white window frames, and the purely decorative tower.
To the left, organic shapes and sculpture on P.L. Kramer's Bijenkorf department-store in The Hague (finished 1926), and to the right the more modest shapes of J. Crouwel's postoffice in Utrecht (finished 1924).