Hamburg-born German architect. He is said to have studied his subject under von Gärtner in Munich (1825), though this is doubtful, but he definitely worked under Gau in Paris from 1826, where he became acquainted with Hittorff's theories of polychromy in Ancient Greek architecture. From 1830 to 1834 he travelled in Southern Europe, and in 1834 he published Vorläufige Bemerkungen über bemalte Architectur und Plastik bei den Alten (Preliminary Remarks on Polychrome Architecture and Sculpture in Antiquity), a pamphlet dedicated to Gau, which created quite a stir. Partly as a result of this publication he was appointed Professor at the Dresden Academy of Fine Arts the same year. While at Dresden (1834–49) he designed some of his best buildings, including the Hoftheater (Court Theatre—1838–41, destroyed), a Cinquecento Revival building with an exterior that made clear what were the internal arrangements, not uninfluenced by F. Gilly's design for a National Theatre of the 1790s. This structure was replaced after a fire with the celebrated Opera House, also designed by Semper, and built 1871–8 under the direction of Semper's son, Manfred (1838–c.1914). It was destroyed in 1945 but rebuilt in the 1980s. It is arguably his greatest achievement, one of the most beautiful theatres in the world. He also designed the eclectic Synagogue (1838–40—destroyed 1938) in a mix of Byzantine, Lombardic, Moorish, and Romanesque styles, with a polychrome interior of great richness; the Villa Rosa in a Quattrocento manner (1839—destroyed); the sumptuous Oppenheim Palais in Cinquecento Revival (1845–8—destroyed); and the Gemäldegalerie (Picture Gallery) attached to Pöppelmann's Zwinger (1847–54—restored 1955–6 after war damage). In 1835 he designed the polychrome ‘Antique’ rooms in the Japanese Palace, Dresden, which caused a sensation because of their vivid Classical beauty.
Having fallen foul of the Saxon authorities after the 1848–9 revolution, Semper went first to Paris and then to London, where he met Henry Cole the energetic member of the 1851 Exhibition committee, in 1850. Semper gained valuable introductions through Cole, and designed the Canadian, Danish, Swedish, and Turkish sections for the 1851 Exhibition in the Crystal Palace. His connections and his book, Wissenschaft, Industrie, und Kunst (Science, Industry, and Art—1852) brought him to the attention of Prince Albert, who was greatly interested in Semper's ideas about the relationship between architecture, design, industry, and education. Semper taught design while in London, but his most remarkable achievement was his detailing of the great funeral-car for the Duke of Wellington's exequies (1852). Disappointed with his lack of opportunity in London, however, he took up a teaching post at the Zürich Polytechnic, where he remained until 1871. While there he designed the fine Zürich Polytechnikum (1855–63—now ETH, Zürich), and made designs for his friend, the composer Richard Wagner's (1813–83) proposed (but unrealized) Festspielhaus (Festival Theatre—1864–7) for Munich which influenced the building (1876) designed by Brückwald that Wagner eventually succeeded in erecting in Bayreuth. Semper won the competition to design the Town Hall at Winterthur, Switzerland (1862—built 1865–70). In 1851 Semper had published Die vier Elemente der Baukunst (The Four Elements of Architecture) in which he identified those elements as hearth, platform, roof and its supports, and non-structural enclosure (of textiles, etc.) to keep out the weather. Having seen a Caribbean hut at the Great Exhibition, he found these four elements perfectly expressed, but believed that each of them could be subject to transformations, together or separately, and that those transformations could become rapid in a period of industrialization and change, as normal evolutionary processes would be subjected to enormous outside pressures. He went on to develop his ideas in his most important book, Der Stil in den technischen und tektonischen Künsten, oder praktische Äesthetik (Style in the Technical and Structural Arts, or Practical Aesthetics—1861–3), which proposed that artefacts and architecture acquire meaning from the ways in which they are made and from their functions, so Semper described materials and their uses, investigating how design motifs appeared and how those motifs were transferred from one material or context to others. In architecture, he noted how traditional and familiar forms retained traces of very early, primitive uses. In Semper's theory he conceived four essential categories of making artefacts: weaving (producing textiles and patterns); moulding (creating pottery from clay); carpentry (providing essential structures of timber, especially walls, partitions, and roofs); and masonry (involving building with stone for hearth, walls, piers, etc.). To the four processes he added working with metal, and came to the conclusion that the greater part of the forms used in architecture actually originated in those processes (now five) themselves. From these he derived his theory of style, and argued that architecture was reducible to the materials and processes associated with their uses. Semper believed that long before Man made a building he evolved patterns (e.g. in weaving, which he called Urkunst, or original art, meaning the source of art, providing prototypical models), and that these preceded the evolution of structural form, so ornament, far from being an afterthought, was actually more basic and symbolic than structure. He further developed his theory to postulate how political, religious, and social institutions create conditions by which appropriate and poetic expression is given to architectural forms. Thus architecture should be expressive of its purpose and the parts of a building easily distinguished. This is very far from the ‘materialist’ and ‘functionalist’ position he is often held (by those who either have not understood his (admittedly) prolix texts, or who have distorted his meanings for reasons of their own) to have adopted: in fact he stated that his conception of basic forms and their origins was the antithesis of the view which held that architecture was nothing more than evolved construction, a demonstration of statics and mechanics, and a pure revelation of material. For example, he noted that the patterns and ornaments used in producing textiles might reappear on walls constructed of other materials, while swags or garlands on several buildings often reappear as sculpted or painted elements on friezes, and in their transformations the materials used are of no great importance. Claims for Semper as a proto-Modernist are as absurd as those which hold Baillie Scott, Voysey, et al. were forerunners of the Bauhäusler, for he derided Viollet-le-Duc as a materialist, and could not accept that monumental architecture could be created using iron structures (he did not approve of Paxton's Crystal Palace). He was, however, an influence on Semiotics (see semiological school).