He was also a partner in the firm of Messrs Joseph, whose best known building is Shell Mex House between the Strand and the Thames Embankment in London.
He was one of six children of Nathan Solomon Joseph (1834–1909), also an architect and social worker, and his wife Alice who died in his infancy.
Ernest Joseph was educated at St Paul's School and devoted himself to Jewish youth from his twenties until days before his death.
In the First World War he worked to provide buildings for what later became the NAAFI and was promoted Major and appointed Member of the Order of the British Empire.
Ernest became Honorary Architect to the Union of Liberal and Progressive Synagogues and was responsible for the design of their premier building at St John's Wood in 1925 and for its reconstruction after bomb damage in November 1940.