Mewès's hotels, steamer interiors, clubs, and private residences suited the Edwardians' opulent taste.

His first maritime interior, the Hamburg America Line's SS Amerika was completed in 1905; the company so admired it that Mewès became their resident designer.

Although Mewès only spoke French, he opened firms in both London and Cologne, Germany, with Arthur Joseph Davis, who had been his classmate at the École des Beaux-Arts, and with the Swiss Alphonse Bischoff.

In October 1947 the journal of the Royal Institute of British Architects described him as "The true type of the French intellectual of good stock".

Charles Mewès bought the small castle of Scharrachbergheim in Alsace, where he spent much time with his three children after the death of his wife in 1896.