Earlier 17th century origins possibly of longhouse type; extended to uphill and partly remodelled in 19th century. The whole building later re-windowed and the middle section converted to a Music Room in 1930s as part of Clough Williams-Ellis' improvements to the Plas Brondanw estate.
Rubble construction with massive quoins and pronounced boulder plinth. Slate roofs, partly roofless to middle in 1990s. Rubble chimney stacks at both ends.
Comprises 2-storey, 2-bay, dwelling to low end, single storey, 2-bay, domestic part to middle and single storey, 1-bay unit to uphill end
(Source: CADW file, (Mer. Dom. SH64 NW/NE/SW))

H.C. Vieth, RCAHMW, 31 January 2005

[Additional:] Tree-ring dating commissioned by Cymdeithas Hanes Beddgelert in association with RCAHMW. Results published in Vernacular Architecture 37 (2006), List 181 (notes by Margaret Dunn, Daniel Miles, and Richard Suggett):

10. LLANFROTHEN, Hafoty, Croesor (SH 6312 4325) Felling dates: Summer 1760 to Spring 1766
Joists 1765(50?C), 1760(28?C); Upper crucks 1760(41?C, 25?C); Purlin 1763(32?C); Collar 1760(28?C), Mantel-beam 1760(16?C); Transverse/tiebeam 1759(20?C); Cleat (0/1). Site Master 1581-1765 BDGLRT5 (t= 7.0 WALES97; 5.4 EASTMID; 5.4 CBMSQ02)
A storeyed cottage-farmhouse (tyddyn) in a range with former farm buildings. The dwelling has a two-unit front range with a rear service wing. It is dominated by a large kitchen end-fireplace with arched beam. The trusses are of upper-cruck type, with lapped `wavey' collars, set on roughly chamfered beams. The tree-ring dates show that the timber used was felled over a period of several years. The graffiti date of 1773 on the fireplace beam is significantly later than the latest felling date of 1766.

R.F. Suggett/RCAHMW/2006