Gerlan lies to the south of Bethesda, separated from the main town by the river Llafar. It was built within ten years of Bethesda acquiring Improvement Commissioners in 1854 and was consequently 'set out on straight roads of the statutory width of 6.4 metres (21 feet).' Owners of the houses 'could choose their house design and build either separately or in partnership with their neighbours' although most of the houses 'follow the two-up-two-down pattern of industrial housing'

Source: 'Welsh Slate - Archaeology and History of an Industry' by David Gwyn (2015, RCAHMW)