Coed Helen is thought to be an early seventeenth century house, largely remodelled in the nineteenth century and partly rebuilt in the mid twentieth century. It is made up of three parallel three storey gabled blocks, aligned north-east to south-west. These are joined by short wings producing something resembling a mirrored E plan. The form of the original house is uncertain. The two northern wings have complementary asymmetric gables. The southern wing is modern. The OS County series 1st edition (Caernarvon. XV.4 1888) shows what are probably lesser service wings on the southern side.

The northern range has a five window facade in which there is a gap between the three western and two eastern window rows. The range's west gable retains the original chimney and stack and there is a tablet inscribed 1606 in the eastern gable. The central range appears to have original ground and first floor beams. Vertical paneling in the western ground floor room is largely modern and the staircase is thought to retain some original material.

The house is set within extensive grounds, portrayed in some detail by the Ordnance Survey in 1888, and now a caravan park. There were walled gardens to the north-east of the house and a drive or lane wound round to the Caernarvon Ferry. An embattled late eighteenth century summer house crowns the summit of the hill between the house and the Seiont estuary (NPRN 23012). There were scattered trees in the fields around the house and grounds, intended to produce a park-like effect.

Sources: RCAHMW Caernarvonshire Inventory II (1960), 158 No. 1124
NMR Site File

John Wiles, RCAHMW, 2 July 2007