Reconstruction drawing by Falcon Hildred showing the collar-beam truss at Tŷ-Mawr, Nantmor. Tŷ-Mawr is a small, dry-stone house situated in Snowdonia on a level spot on the mountain slopes above Nantmor in the parish of Beddgelert. Although modest in appearance, the plan, features and the quality of its masonry and carpentry shows us that this was a small-scale hall-house of gentry-status. Tree-ring dating commissioned by the Dating Old Welsh Houses community project tells us the timbers used in its building date from 1529.