Renovation of the 922 windows in the palace started at the beginning of the 1990s. The age of the windows varies from the mid-18th century to the 1970s. The reason for the renovation was that the windows had not been properly maintained for a number of years. The windows on the south side were the most exposed and the sun had burned the surface causing rot. The renovation of the windows was carried out in collaboration with the National Property Board of Sweden, the Office of the Governor of the Royal Palaces, the Swedish National Heritage Board and the Royal Architect at that time, Ove Hidemark. The work was done in a workshop at the Inner Courtyard and took about ten years. Each window was custom made for the opening where it was originally placed, making the size and shape of each window unique.