When Aniston, 43, bought the Bel Air mansion in January it boasted four bedrooms, six bathrooms and multiple fireplaces.
But, according to the Mail Online, the actress has ordered extensive changes including ripping out the on-site vineyard and replacing it with a Jacuzzi and a pool.
Meanwhile Aniston has been spotted perusing posh Los Angeles furniture stores looking for the perfect pieces for her new home.
Construction on the property, which sits on the Santa Monica Mountains and overlooks the Pacific Ocean, is not expected to finish until 2013. In the meantime Aniston and Theroux have been spending a whopping $40,000 a month to rent a five-bedroom, six-and-a-half bathroom home in Beverly Hills.
Whether or not the couple will be married by the time their Bel Air mansion is complete is unknown. But it is clear the Wanderlust co-stars are happy with their life together. The lovebirds were all smiles when they attended the 26th American Cinematheque Award Gala in Beverly Hills last week.
And while she has snagged a hunky fiance and a fancy house, Aniston says she doesn't need a baby to make her life complete.
She told the Spanish edition of GQ earlier this year: "A perfect life? I think that's sort of cliche, isn't it?
"Like, if you want to be happy you should have the house, the husband, the kid… Kids are messy!"
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