The first residential houses in Lebanon were the Phoenician houses.[15] They were bricks and the roofs where always formed from huge rocky segments. The perception deriving the method of building a house met some changes after the third millennium BC when the walls of the houses increased in height, some houses were built with stones, others remained rectangular and all increased in dimensions.[citation needed] The exterior and the interior walls where covered sometimes with mud.[citation needed] Lebanese houses incorporated the rules of the Ottoman Empire and the exit of the French mandate.