William was the fifth of six children and second son of John Waymouth (cooper) and Mary (nee Penn) of Millbrook, Cornwall.
William trained as a builder in Exeter but on 3 January 1838, when he married, he was a surveyor living in Peckham Rye, a newly developing area in South London.   He married Catherine Dubberley (nee Omer) (see) and they moved to Islington in North London where their three sons were born: William John Waymouth (see), Frederick Waymouth (who died young) and George Waymouth (see).   In the birth registration of his son, William John (born 1838), William is recorded as an architect and surveyor.

The probate summary for William said that he was of 35 Canonbury Park North, Middlesex and of Moorgate Street, City of London, architect, who died on 30 June 1888 at 35 Canonbury Park North.   Will proved at London on 14 July 1888 by George Waymouth of Angleside, Blythwood Road, Hornsey, Middlesex, architect, son and sole executor.

William was buried at Abney Park, Stoke Newington.   His wife, Catherine, and son, Frederick, were also buried there.