In most households, cooking was done on an open hearth in the middle of the main living area, to make efficient use of the heat. This was the most common arrangement, even in wealthy households, for most of the Middle Ages, where the kitchen was combined with the dining hall. Towards the Late Middle Ages a separate kitchen area began to evolve. The first step was to move the fireplaces towards the walls of the main hall, and later to build a separate building or wing that contained a dedicated kitchen area, often separated from the main building by a covered arcade. This way, the smoke, odors and bustle of the kitchen could be kept out of sight of guests, and the fire risk lessened. Few medieval kitchens survive as they were "notoriously ephemeral structures".