Champneys was born in Whitechapel, London, in 1842 where his father was the vicar of St Mary's Church.  He attended Charterhouse School and then Trinity College, Cambridge.  Following university he studied as an architect with John Prichard, the Surveyor of Llandaff Cathedral.  He set up his own architectural practice in 1867 in  London.  Among his commissions was a library for Mansfield College, Oxford, and it was this building that impressed Enriqueta Rylands and prompted her to commision Champney's to design the library on Deansgate to commemorate her husband John.