The couple, who have been together for 11 years have three children and live in adjoining houses as they need space from one another.
The 45-year-old actress said that not living together does not mean their relationship is not serious, reported Contactmusic.
"We are not (married), actually because of the laziness, really. Our houses are married. It is very good to have. You definitely need your space," she said.
Carter and Burton, 53, have worked on seven movies together. The "Harry Potter" actress thinks it is important that she gets to see him work, otherwise she would worry about the filmmaker's stress levels when he came home in the evenings.
"He is very stressed. Directors are. The stress level, it is a battle. I mean everything that can go wrong goes wrong," she added.