The addition of glass construction to heighten the building occurred in 1963.

Later additions to the house occurred in the 18th and 19th centuries.

The last major addition occurred in 1895 when Stanford White enlarged the west drawing room.

The final addition to the building occurred in 1923.

Several other additions and renovations have occurred since the 1970s.

Then, the oxidative addition of a second silane unit occurs.

Many additions have occurred over the years, including in 1923, 1956, 1968, and 1982.

More recent research has confirmed that such additions occurred.

Another major addition occurred in 1966 with the construction of the large east wing.

An addition of a wing to the south of the original building occurred in 1953-1954.