[1] He studied architecture at the Royal Academy of Arts from 1909 to 1912 and during that time worked with Edwin Lutyens in London[2] After returning to New Zealand he entered a partnership with Wellington-based firm Hoggard and Prouse, creating the firm Hoggard, Prouse and Gummer.

He worked in the firm's Auckland office on High Street.

[2] Many of Gummer's buildings are listed with Heritage New Zealand; often they are classed as Category 1.

His own house, Stoneways in Epsom, is also listed as Category 1.

[6] In 1953, Gummer was awarded the Queen Elizabeth II Coronation Medal.