One of the two most imaginative English Baroque architects (the other was Vanbrugh), he worked with Wren, notably on the Chelsea Hospital, St Paul's Cathedral, and the City Churches, all in London. He was Clerk of Works (1689–1715) at Kensington Palace (where he supervised the building of the Orangery (1704–5—probably designed by Wren, with revisions by Vanbrugh and Hawksmoor), and was Clerk of Works (1698–1735) at Greenwich Hospital, where he played a major role in the design of the east range of Queen Anne's Court and the dormitories in King William's Court. In 1715 he also became Clerk of the Works at Whitehall, Westminster, and St James's, as well as Secretary to the Board of Works, which made him a senior official of the Royal Works. Vanbrugh engaged his services at Castle Howard, Yorks., and Blenheim Palace, Oxon., and it is now clear that the skills Hawksmoor had acquired under Wren enabled the architecturally untrained Vanbrugh's schemes to come to fruition. By 1700 Hawksmoor had evolved his original style, as is evident from Easton Neston, Northants. (c. 1695–1702), a large country-house (in the design of which, however, Talman may have played a greater role than recognised hitherto), and over the next decades demonstrated his assured knowledge of the Classical vocabulary as well as its imaginative application. He understood the tensions and possibilities of the juxtaposition of masses of masonry, and exploited the drama and power of modelling, light, and dark in his vigorous designs.
Hawksmoor was appointed one of the two Surveyors (the other was Gibbs) to the Commissioners for Building Fifty New Churches in London under the Act of 1711 and in that capacity he designed six of the most original churches in and near the capital: the body of St Alphege, Greenwich (1712–14), St Anne, Limehouse (1714–30), St George-in-the East, Wapping (1714–29), Christ Church, Spitalfields (1714–29), St Mary Woolnoth, City of London (1716–24), and St George, Bloomsbury (1716–31). St Alphege's is in the form of a temple, with a huge serliana at the east end; St Anne's has a powerful tower with a crowning lantern like a medieval element in Classical clothes; St George-in-the-East has four pepper-pot staircase-towers and a curious top to the western tower formed of altar-like drums; Christ Church, Spitalfields, has a broach spire set above a gigantic serliana porch; St Mary Woolnoth has powerful Baroque modelling; while St George Bloomsbury has an immense Roman temple portico and a tower crowned with a stepped pyramid derived from descriptions of the Mausoleum at Halicarnassus. From these buildings the interests of Hawksmoor may be deduced. He was bookish (he had a considerable library), steeped in a love of Antiquity, fascinated by English medieval architecture, and intrigued by the possibilities of freely interpreting the great buildings of the past from descriptions. Some of his work is derived from earlier French publications showing images of supposedly Antique buildings, which partially explains the element of fantasy in his designs.
Hawksmoor often introduced powerful emotional contents: at the Mausoleum, Castle Howard (1729–42), for example, the peristyle of his circular Roman-temple form is a Doric Order, but the unfluted columns have only one triglyph over each intercolumniation, giving a brooding solemnity to the architecture, influenced perhaps by Bramante's tempietto at San Pietro in Montorio, Rome. The Clarendon Building, Oxford (1712–65), also employs closely packed unfluted Roman Doric columns as well as inventively oversized keystones and oddly placed guttae. He also designed in the Gothic style, as at All Souls College, Oxford (1716–35), and the western towers at Westminster Abbey, London (designed 1734 and completed by J. James (c.1745). Some of his inventions, such as the Carrmire Gate, Castle Howard (c.1730), with its steep pyramids, powerful modelling derived from Serlio, and emphatic qualities, combine the primitive, allusions to Antiquity, and a fascination with geometry, anticipating the most robust and stripped language of late-C18 Neo-Classicism. He also designed the Pyramid eyecatcher at Castle Howard (1728), the obelisk in the Market Place, Ripon, Yorks. (1702), and (with James) the Church of St Luke, Old Street, London (1727–33), with its obelisk-spire. In its essentials, Hawksmoor's architecture is primarily a demonstration that in geometry lies the key to all order, all creation. One of his last designs to be realized (with modifications by its builder, Townesend) was the screen-wall and entrance at Queen's College, Oxford (1733–6), on the High Street.