17th century or earlier, with 18th centruy arm later alt/add 'L' plan. 2 Storey. Rubble small grouted slate roof. Recessed windows. Hewn beans. On the north side is a wheelpit which formerly housed a waterwheel driving a gorse mill or butter churn.

Additional:

Tree-ring dating commissioned by Cymdeithas Hanes Beddgelert with RCAHMW. Results reported in Vernacular Architecture 38 (2007). Notes by Richard Suggett, Daniel Miles, Margaret Dunn:

5. BETWS GARMON, Llwyn-bedw (SH 5300 5826) Felling date: Winter 1584/5
Secondary ceiling beam 1584(47C, 42C); Axial beam (0/1); joists (0/2). Site Master 1504-1584 BDGLRT12 (t = 5.5 CLRENDN7; 5.4 OLDHLLFM; 5.2 WILBURY1; 5.1 BERRYPOM)
A stone-built, storeyed, sub-medieval house of Snowdonian type with gable-end chimney, situated by a knoll at 130m O.D. above the valley bottom.. A parlour wing (possibly of earlier date) has a mutilated plaster overmantel with part of a shield bearing the coat-of-arms of Collwyn ap Tangno. The earliest documentary reference (1583) matches the felling date (1584/5) obtained from the hall ceiling. Further details in NMRW with plan in RCAHMW, Caernarvonshire Inventory II (1960), 34., fig. 34.
R.F. Suggett/RCAHMW/July 2007.