In 1880 he designed the United Reformed Church in Wonersh, the Kingham Hill School in Oxfordshire in 1886 in the traditional Cotswold style (completed in 1903),[4] Marling School in Stroud from 1889 to 1894 and in 1892 proposed an extension of the Camden Chapel, in Camberwell, Surrey but was rejected.
[1] In 1896 he designed a memorial in St Paul's Cathedral for General John Inglis, with bronze reliefs by Derwent Wood.
[1] That same year, Seth-Smith drew up plans for the St. Thomas Church in Chilworth and made additions to The Royal Liberty School, on Upper Brentwood Road in Romford; notably the porch, garden rooms and vestibule.
From 1905 until shortly before his death he was in an architectural partnership at 46 Lincoln's Inn Fields, London with William Ernest Monro.
[1] He was also a keen water colour painter, and exhibited some of his works at the Royal Academy of London.