"Brad pores over architectural journals like other people pore over newspapers. He had so much fun putting the run together with his kids Maddox, Zahara, Shiloh and Pax,” the Sun quoted a source as saying.
"It's incredibly complex and cost a lot but Brad''s more than happy with any activity that can combine his two passions - his kids and architecture," the source added.
The Inglourious Basterds star has always had a penchant for architecture, and even had an informal apprenticeship with Frank Gehry, the renowned architect, in 2005.
Pitt has also engaged himself in designing a development for the seafront in Hove, East Sussex, but the project is still unfinished.