Cwmorthin Terrace was a two-storey terrace of 13 cottages, with gardens on the north side sloping down towards the lake, and small yards with privies (built in pairs) on the south side. The terrace was built in two phases between 1860 and 1880, the first comprised of eight houses built from rubble (county rock) with roughly-cut dressings and was completed before the census of 1871 when the first inhabitants are listed. The second pahse of six houses was cnstructed from slate waste blocks, some of which were sawn.

Each cottage seems to have had only two rooms, one up and one down (there may have been wooden partitions), and the 2nd phase cottages had massive downstairs fireplaces. The walls of the 1st phase buildings now stand no more than first floor height, and the adjacent slate-built cottage has almost disappeared, but more of the other 2nd phase cottages survive, two gables still complete with their chimneys.

Recording and conservation work on the building is being undertaken by the Cwmorthin Project (2014)

W J Crompton, RCAHMW, 17 December 2008.
Louise Barker, RCAHMW, February 2015