On 22 March 1911 he married Elsie Helena Blunt, a milliner, at St Martin's Anglican Church, Kensington.

[1] After the death of his sister Mary in 1917, Walder and his wife helped raise his nephew William McMahon, who would eventually become Prime Minister of Australia.

[1] In December 1924, Walder was elected to the Sydney City Council at a by-election for Flinders Ward, standing for the Civic Reform Association.

[6] During World War II, Walder chaired Sydney City Council's National Emergency Services committee, advocating the construction of underground air-raid shelters and other measures preparing for possible attack.

[4] Survived by his wife, son and daughter, he died of cancer on 24 November 1946 at Woollahra and was buried in Waverley Cemetery.