Philip (christened (Phillippe) Speakman Webb was born in Oxford on 12 January 1831, one of the eleven ('all obstinate') children of Charles Webb, an Oxford doctor and his wife Elizabeth Speakman. He was educated at Aynho Grammar School, Northamptonshire and articled early in 1849 to John W Billing of Reading, completing his articles in 1852 and remaining as assistant until 1854. He then moved to the office of Bidlake and Lovatt of Wolverhampton, with whom he remained only four weeks, returning to Oxford as chief and for a time only clerk to George Edmund Street in succession to Edmund Sedding. Early in 1856 Webb became responsible for William Morris as Street's articled pupil, and later that year Street moved his practice back to London. Morris stayed with Street only a year, but he and Webb remained close friends and quickly attached themselves to the Pre-Raphaelite circle, particularly the Rossettis and Edward Burne-Jones who shared Morris's rooms at 1 Upper Gordon Street. In August 1857 Webb made a study tour of northern England and Scotland and in August 1858 another of northern France but, unlike Richard Norman Shaw and William Eden Nesfield, he did not publish.
In 1859 Webb left Street's office to set up independent practice at 7 Great Ormond Street, his first client being the newly married William Morris for whom he built the Red House, the original intention being that it would become a collegiate community where all of Morris's circle would live. This concept was not pursued but commissions for larger houses at Benfleet (1860) and Arisaig (1863) quickly followed and out of the furnishing and decoration of the Red House grew Morris, Marshall, Faulkner & Co, founded in 1861 for which Webb designed most of the furniture and some of the glass, as well as being consulting manager, the day-to-day manager being Warrington Taylor with whom Webb and the Morrises made a tour of France in 1866.
The style of Webb's early houses grew partly out of his studies of vernacular architecture and partly out of the simpler architecture of Street and of William Butterfield, whose friendship he enjoyed and with whom he maintained a correspondence which partly survives. Also very much part of Webb's circle in those earlier years was George Frederick Bodley whose practice Webb managed while he was convalescent in Brighton in 1869.
In 1864 Webb moved house and office to 1 Raymond Buildings, Gray's Inn and the practice began to acquire a more aristocratic character through the support of the artist George Howard, Earl of Carlisle and his Stanley sisters-in-law, one of whom brought the 1868 commission for alterations at Cortachy Castle. Webb's proposals for a new wing were aborted, probably because Webb's architecture proved too astringent and his character too uncompromising, Bryce taking over from him in 1870.
Webb's direct involvement with Morris, Marshall and Faulkner came to an end in 1875 when the original company was dissolved and refounded as Morris & Co, Webb renouncing £640 in arrears of salary. In his middle years he worked with only a couple of assistants of whom there is record of George Basset, Thomas Charles Yates and ____ Buckle, subsequently architect to the diocese of Bath & Wells. In 1880 George Jack came from Horatio Kelson Bromhead's practice in Glasgow as assistant and remained with him: he was joined by William Weir in 1889. But although the number of architects who worked with him remained few and only at the very end of his career did he allow his work to be published, his influence spread widely through the Society for the Protection of Ancient Buildings, founded by Morris in 1877, profoundly influencing the London County Council Architect's Department.
In 1883 Webb - who had no religious beliefs - became a socialist, initially through the influence of Morris. It did not affect his business any more than it did Morris's, his predominantly conservative clients remaining loyal, but in 1889 he had a serious attack of rheumatic fever. By 1897 he was beginning to consider retirement, partly because of declining strength and partly because of the relatively high rent of his Gray's Inn rooms and office. In September 1899 he gave notice of his intention to end the lease and in the following year transferred his practice to his assistant George Jack, a year-long search for a retirement cottage ending with the lease from Wilfrid Blunt of Caxtons, Worth, Sussex. As a result of a severe illness in the winter of 1902 he did not draw again, but he travelled a little in England and continued to receive and advise old colleagues and a wider circle of Arts and Crafts disciples.
Webb never married. His practice never made much money, partly because his staff, two strong for most of his career, were fairly generously paid by the standards of that time. Although he lived frugally and his needs were few, in his final years he began to run out of money, his bank account being unobtrusively topped up by George Jack until he died on 17 April 1915. His remains were cremated and his ashes scattered at White House Hill.