This building has a fairly large base, and it requires a large number of items to actually construct:

• 10 Stone Blocks
• 8 Gold Bricks
• 12 Hammers
• 8 Light Breakfasts

The Light Breakfasts are earned via a general news post on your wall, while the Stone Blocks can either be crafted or earned by asking your friends to send them to you via individual requests. The Gold Bricks and Hammers need to be crafted manually. Once you've finished this Royal Chateau, you'll be able to collect 2,500 coins in profits, eventually making this building profitable.

All told, there doesn't seem to be a time limit for building this Royal Chateau, nor has a quest been released requiring you to construct it. If, however, you just like the look of this building, or need something to do while waiting for new quests to be released, you can now do just that.