I have been to Versailles a couple of times, but it was years ago. The palace is in an almost perpetual state of restoration. As with all palaces, it went through many modifications even while still in use as a royal residence. For instance, the famous Ambassador Staircase was removed in, I think, Louis XV's time, to make way for some additional rooms. Also, the ground floor gallery was originally open to the air but later enclosed by Louis XIV to provide an exercise space for rainy-day walks.
The biggest alterations, of course, came after the Revolution, when some of the state rooms were converted to museum galleries glorifying the French military exploits of the 19th century.
By the early 20-century, the palace was in an advancing state of decay. John D. Rockefeller came to its aid in the 1920's, at which time structural engineers and restorers made their first descent on the place. As you might expect, the initial focus was on the major state apartments and the suites of the royal couple.
Some of their findings were startling. Louis XIV had built Versailles "on the cheap", as it were. For instance, many of the fountains were in near collapse, because they were made of cement poured around bundles of flagons in an attempt to cut costs.
The restoration of Versailles today seems to be well-funded and moving along apace. Last I heard, the restorations had been extended into the ground-floor quarters of other members of the royal family.
In its heydey, Versailles was home to around 10,000 people. While the members of the royal household lived in relative comfort and privacy, some astonishingly high members of the nobility were relegated to pretty ratty quarters in the garret floors, where they had one or two small poorly-ventilated rooms, where people urinated in hallways and stairwells, etc. Maybe not much of a problem in those days . . . Louis XIV himself was reported to have seen a bath only twice -- upon being born and being embalmed.
