Ancient Irish Church - Unusual Doors

Not only were church buildings small, in St. Patrick's day, they had unusually appearing jambs for doors and windows. P.W. Joyce describes them in A Smaller Social History of Ancient Ireland:

...The jambs of both doors and windows inclined, so that the bottom of the opening was wider than the top: this shape of door or window is a sure mark of antiquity. The doorways were commonly constructed of very large stones, with almost always a horizontal lintel: the windows were often semi-circularly arched at top, but sometimes triangular-headed.