The Hafod Arms was originally built in 1787 by Thomas Johnes of Havod as a small hunting lodge, and rebuilt by Johnes in 1801-1803 and 1814-1915 as a hotel. The present hotel is largely the result of yet another rebuild of 1838-1839 by the Fourth Duke of Newcastle which thoroughly repaired the existing structure and nearly doubled its size. The plans of the 1839 building were allegedly designed by the Duke himself, but where in fact the result of his builder, S. Heath, modifying plans by William Coulart of Aberystwyth. The building was not entirely rebuilt, however, likely retaining the 1814 windows of the front range. The hotel was purchased in 1864 by the Hafod Hotel Company (which went bankrupt soon after) and further alterations in the 1860s added a billiards room to the south-east rear of the building and new a dining room. A lithograph produced in this decade shows substantial differences from the current structure, including a two-storey stone range with large two- and three-light mullioned windows and central chimney, to the left of which was a walled courtyard. The main entrance is also in the fourth bay (rather than in its current central location) and is flanked by two bay windows, and there are also differences with the outbuildings behind the hotel. The single-storey tea room range fated from the early-twentieth century at latest and may have been part of alternations of 1904 and 1925 by G. T. Bassett for F. P. Lightfoot, who was then the owner. The building was restored in 1902 by Roscoe & Bean of Shrewsbury, and has undergone further restoration and improvement since it was purchased by the present (2018) owners in 2016.

Externally, the main range of the building three-storeys high with an attic and five symmetrical bays wide, constructed of rubble stone. It is noted for its distinctive alpine-style slate roof with very broad overhanging eaves carried on giant brackets formed of horizontal beams supported by vertical beams and curved braces on corbels. The roof has gabled dormers to the front and four to the rear, each with a square double window divided by a transom and deep bargeboarded gables. The third-storey of the front has a square sash window in each bay, under which are rectangular sash windows in the second-storey. The first storey has rectangular sash windows in the first and second bays and canted bay windows in the fourth and fifth bays. In the central bay is the entrance: pointed arched door in a pedimented porch with tapered square pillars. The eastern gable end has a large arched window extended from the second to the third storey, under which is a canted bay window. To the left of these are three rectangular windows in the first, second, and third storeys. The western gable end has a small third-storey door. Behind this wing is a two-storey rear extension to the south east under a catslide roof and the billiards room with pyramidal roof topped with a louvred ventilator. To the west of the main range is a single-storey tea room with a slated roof carried over a front veranda supported on square pillars, with a prominent square stone chimney in the western gable end. To the west of this is another single-storey range built of coursed stone. It has a double door surrounded by twelve lights to right and left and a range of six lights with large lozenge tracery above, to the right of which is a large window. To the west of this range is yet another single-bay, two-storey range: The Three Bridges Bar. It is built of coursed stone with a deep-eaved roof (albeit not to the extent of the main range) with the gable end facing front. The second story contains a large square window while the lower storey has a deep-sunk double door, to the left of which is a large corner window. The pub sign displays a picture of the nearby Devil's Bridge (Nprn 23859). To the rear of the hotel are several outbuildings (Nprn 96398). On the eastern side of the building is a grade II listed Automobile Association call box.

(Sources: Cadw listed buildings database; `Devil's Bridge and Hafod Arms Hotel?, image, c.1860, National Library of Wales; `?Hinterland? Hotel to undergo a complete revamp following sale?, Wales Online, 12.07.2016; Lloyd, Orbach, and Scourfield, Buildings of Wales: Carmarthenshire and Ceredigion (London: 2006), p. 465.)
A.N. Coward, RCAHMW, 11.05.2018