Codman spent much of his youth from 1875 to 1884 at Dinard, an American resort colony in France, and on returning to America in 1884, studied at the Massachusetts Institute of Technology.

In her autobiography, A Backward Glance, Wharton wrote:[5] We asked him to alter and decorate the house—a somewhat new departure, since the architects of that day looked down on house-decoration as a branch of dress-making, and left the field up to the upholsterers, who crammed every room with curtains, lambrequins, jardinières of artificial plants, wobbly velvet-covered tables littered with silver gew-gaws, and festoons of lace on mantelpieces and dressing tables.

Codman was not a draftsman, and it is said that in Paris he hired a talented group of students from the École des Beaux-Arts to draw up the sketches for Vanderbilt.

His suave and idiomatic suite of Régence and Georgian parade rooms for entertaining are preserved in the townhouse at 991 Fifth Avenue, now occupied by the American Irish Historical Society.

The New York City Landmarks Preservation Commission later described the facade of number 7 as being "full of gaiety and frivolous vitality" and further, "on approaching the house, Paris and the Champs-Élysées immediately come to mind."

In 1920, Codman left New York to return to France, where he spent the last thirty-one years of his life at the Château de Grégy, wintering at Villa Leopolda in Villefranche-sur-Mer, which he created by assembling a number of vernacular structures and their sites: it is his masterpiece, the fullest surviving expression of his esthetic.

[3] In 1918, Codman leased the former Newport cottage of society leader James Vanderburgh Parker, known as "Sans Souci" and located on Merton Road, for the summer.