Churches, castles and manor houses were already being built of stone during the early medieval period, but it was not until the late 12th and 13th centuries that the timber walls of peasant houses in almost all stone-producing areas were replaced by walls built of stone (Beresford and Hurst 1971, 93–95). Comparatively few medieval mason’s tools survive, but they are frequently mentioned in building accounts (Salzman 1967, 123–124, 330–340), and representations of building work most frequently depict work on stone buildings.