Warfare and plague helped to make the 14th century a period when relatively little new building was done. But during the 15th century there was an upsurge of activity in which many Abbeys and other Ecclesiastical buildings were remodelled or extended.
The most striking secular development was the construction of tower houses all over the country. The trend began early in the 15th century and continued until about 1650, so that such towers are the commonest of all pre-modern structures in the Irish landscape. Essentially the tower house is a small-scale castle keep - a usually rectangular tower, most often four or five room-sized storeys high, large enough to house a family and its servants with dignity if not in comfort. There might also be one or more smaller towers or turrets at the corners to hold the stairs and extra chambers. Dunsoghly (County Dublin) is a tower house with four such 'flankers' and, uniquely, its original medieval roof. The tower stood within a walled enclosure, or bawn; most of these have since disappeared (their walls plundered for building stone), but good examples survive at Dungory (County Galway), Knockelly (County Tipperary) and Rathmacknee (County Wexford). Tower houses were also put up in towns; the most fascinating is at Clonmines (County Wexford), where not only the tower but the entire town is ruinous, having been abandoned in the 17th century when sand chocked it harbour.
The very existence of so many tower houses is evidence that life in Ireland remained extremely insecure; a similar development occured in England during the 14th and 15th centuries, but whereas comfortable, unfortified residences became normal during the Tudor period, Irish lords and gentry (and English and Scottish newcomers) found it prudent to live in cramped but strongly defended quarters for a further century and a half. Since this was a period of conquest, plantation, rebellion and civil war, the persistence of tower-house building scarcely requires an explanation. There were nevertheless signs that the balance between security and comfort was beginning to tilt towards comfort. An early but exceptional example is the mansion at Carrick-on-Suir (County Tipperary), built up against the 15th-century castle; it is still a remarkable and rather disconcerting sight. The mansion, an unfortified Tudor manor house dating from the 1580's, perhaps expressed the lordly confidence of its builder, the Earl of Ormonde, the head of the powerful Butler family.
Much more common were mansions that allowed for greater comfort but retained some defensive features. These two early 17th-century 'castles', the never-finished Kanturk (County Cork), whose formidable air is contradicted by the ranges of windows (letting in both light and enemies), and Portumna (County Galway), a large and splendid Jacobean mansion whose defences consist of little more than firing holes around the main entrance. When the upheavals of the 17th century seemed at last to have subsided, new elegent and unfortified residences such as Beulieu (County Louth) began to appear in the 1660's and, despite the interruption of King William's war, heralded an age of fine public and domestic building.