The unique style of great private houses in Scotland, later known as Scots baronial, has been located in origin to the period of the 1560s. It kept many of the features of the high walled Medieval castles that had been largely made obsolete by gunpowder weapons and may have been influenced by the French masons brought to Scotland to work on royal palaces. It drew on the tower houses and peel towers, with their parapets, corbels, and bartizans. The new estate houses built from the late sixteenth century by nobles and lairds were primarily built for comfort, not for defence, although they were often called castles. They retained many of these external features which had become associated with nobility, but with a larger ground plan. This was classically a "Z-plan" of a rectangular block with towers, as at Colliston Castle (1583) and Claypotts Castle (1569–88).