A tower house is a particular type of stone structure, built for defensive purposes as well as habitation. Such buildings were constructed in the wilder parts of Great Britain, particularly in Scotland, and throughout Ireland, beginning in the High Middle Ages and continuing at least up to the 17th century. The remains of such structures are dotted around the Irish and Scottish countryside, with a particular concentration in the Scottish Borders where they include peel towers and bastle houses. Some are still intact and even inhabited today, while others stand as ruined shells.
Tower houses are often called castles, and despite their characteristic compact footprint size, they are formidable habitations and there is no clear distinction between a castle and a tower house. In Scotland a classification system has been widely accepted based on ground plan, such as the L Plan Castle style, one example being the original layout (prior to enlargement) of Muchalls Castle in Scotland.
The few surviving round Scottish Iron Age towers known as brochs are often compared to tower houses, having mural passages and a basebatter, (a thickening of the wall that slopes obliquely, intended to prevent the use of a battering ram) although the entrances to Brochs are far less ostentatious. In Ireland, there are well over 2,000 tower houses extant and some estimate that there were as many as 8,000 built during the Middle Ages. The construction of the majority of tower houses is thought to have commenced in the early fifteenth century AD and lasted until the mid-seventeenth century. After 1580 many lords built fortified houses and stronghouses although tower houses continued to be built until the guns of the Cromwellians rendered such private defenses more or less obsolete. It is possible that many were built after King Henry VI of England introduced a building subsidy of £10 in 1429 to every man in the Pale who wished to build a castle within 10 years, Ireland being under English control at the time (Statute Rolls of the Parliament of Ireland, Reign of Henry VI, pp 33-5) although recent studies have undermined the significance of this grant, demonstrating that there were many similar grants at different times and in different areas. Tower Houses in Ireland were built mainly by the Catholic Anglo-Irish but also by the Gaelic Irish and more recent Protestant and Presbyterian settlers. Many of these structures were positioned within sight of each other and a system of visual communication is said to have been established between them, based on line of sight from the uppermost levels, although this may simply be a result of their high density. County Kilkenny has several examples of this arrangement such as Ballyshawnmore and Neigham. County Clare, although outside English control, is known to have had approximately 230 tower houses in the 17th century, some of which were later surveyed by the notable Irish antiquarian Thomas Johnson Westropp in the 1890s. The Irish tower house was used for both defensive and residential reasons, with many chiefly families building tower houses during the 15th and 16th centuries on their demesne lands in order to assert status and provide a residence for the senior lineage of the family.
Tower houses can also be found in the Mani peninsula in southern Greece; again an area of scarce resources, poverty, spectacular feuding, long lived vendettas, and a history of lawlessness and independence from central authority. A very good description can be found in the book Mani by Patrick Leigh-Fermor.
Most notable in the New World might be considered a focal element of the Mesa Verde Anasazi ruin in Colorado, USA. There is a prominent structure at that site which is in fact called the "tower house" and has the general appearance characteristics of its British Isles counterparts. This four story building was constructed of adobe bricks circa 1350 AD, and its rather well preserved ruins are nestled within a cliff overhang; moreover, other accounts date this ruin somewhat earlier. The towers of the ancient pueblo people are, however, both of smaller ground plan than Old World tower houses, and are generally only parts of complexes housing communities, rather than isolated structures housing an individual family and their retainers, as in Europe.
After initial European tower houses appearing in Ireland, Scotland and England during the High Middle Ages, Toy traces the appearance in other parts of western Europe as early as the late 14th century, especially in parts of France and Italy.