Brideshead Revisited centers largely on its titular setting—the estate of the Flyte/Marchmain family. This proud house has seen substantial change over the course of several centuries, as it has been disassembled, reassembled, and abandoned by the family, as well as repurposed as a military base. The house reflects both the character of its family and serves as commentary on tradition and religion.
Christianity began as an offshoot of Judaism, itself a belief system with an ancient and storied history. Following its incitement, the new religion soon fractured into sects: Catholicism, having its various orthodox variants; Protestantism, Anglicanism, Calvinism, the Baptist Church, Quakers, Mormons, and so on. Each Christian sect "rebuilds" the religion's core tenets, framing them to prioritize certain teachings and interpretations over others.
The Brideshead home, disassembled and reassembled as it has been, serves as an apt allegory for organized religion. Like Brideshead, Christianity has been deconstructed and reformed over time to serve alternative purposes. The Anglican church, for example, formed in part because Henry VIII of England wanted to divorce his wife. The Catholic Church would not permit this, so Henry VIII created his own Christian sect, with himself as the head and principal authority of the church.
Religion—specifically Catholicism—plays an important role in Waugh's main characters' lives, its purpose changing and shifting over the course of many years. The characters approach religion with different intent at different times, their respective relationships to Catholicism changing as they themselves move between identities and life circumstances. The characters are rearrangements of themselves—like Christianity and like the Brideshead home itself.