A garden room will be built onto the existing kitchen at the side of the house, with a pergola added over a patio next to it to give the royal couple added privacy.
A wood store on the grounds is being converted into a sitting room and lavatory, perhaps for William and Kate's police protection officers, while two berths in a four-block garage will be turned into an "equipment room".
Extra trees will also be planted around the house to screen it from view, and a new gate across what is currently a public road will be built, for use by the royal couple only.
Prince George will have plenty of green space to enjoy as he grows up in the grounds of Anmer Hall, which is located just two miles east of Sandringham House, where the royal family gather every Christmas.
The hall's former tenant of 13 years, company director James Everett and his family, moved out of the property shortly after the summer.
William and Kate will continue to use their newly refurbished home in Kensington Palace, Apartment 1A, as their main residence. The 21-room property includes staff quarters, a nursery, extensive living quarters, entertaining space and a walled garden.