Is the biltmore house biggest house?

No, the Biltmore House is not the biggest house. The title of the biggest house in the world goes to Istana Nurul Iman, the official residence of the Sultan of Brunei. Located in Brunei, Istana Nurul Iman has an area of approximately 2.15 million square feet (200,000 square meters) and features 1,788 rooms, including 257 bathrooms and a mosque that can accommodate 1,500 people.