Grant Mansfield’s 16-month-old unscripted company Plimsoll Productions, based in Bristol and London, is opening an US office in spring 2015. Based in Santa Monica, the office will be overseen from abroad by Mansfield and former Discovery Channel executive Andrew Jackson who joined Plimsoll in August as EVP of International Production, charged with developing the company’s U.S. expansion strategy.

One of the first reality projects Plimsoll will shop to U.S. networks this week is Big Family Mansion, based on a format the company recently had commissioned by UK’s ITV. The show brings families – from grandparents and parents to young couples, teenagers and babies – together under one, mansion-sized roof to test multi-generational living.  After listing their individual homes for sale, the relatives will move into a mansion for one month, trying out the house and, more importantly, trying to live with each other in one property. At the end of the month, they must decide whether they would ever move in permanently together or go their separate ways.

Both Mansfield and Jackson have U.S.-based experience. Mansfield served as CEO of RDF USA and subsequently Zodiak USA. Jackson served as EVP of Production and Development of Landmark Series and Specials at Discovery Channel.

“It’s a producer’s dream to create programming on both side’s of the Atlantic,” said Mansfield. “Through drama and humor, Big Family Mansion is a brand new reality format that provides a hugely entertaining window on the ups and downs of buying a home with your extended family.”