Roxborough Castle was a plain 5 bay block of 3 storeys over a high basement was enlarged and remodelled from 1842 onwards by 2nd Earl; his architect being William Murray. Wings were added of 1 bay and 2 storeys over a basement, running the full length of the original block; these were in Murray's rather restrained Italianate style; the original block being given triangular window pediments and similar features so as to match them. The entrance was moved round to the side of of one of these wings, which became the new entrance front; of 3 bays with a low portico.
At the other side of the house, a large office court was built; a feature of which was a row of 4 little octagons with pyramidal roofs, described in the plan as 'larders'. The entrance door under the portico opened into a hall at basement level, from which a flight of steps led to a vestibule in the main block of the house, with the staircase opening off it at one side. The space saved by moving the entrance to the wing enabled a new large drawing room to be formed in the original block; but the proportions of the other two principal rooms, the dining room and library, remained unchanged.
Some time in the C19 the rooms were adorned with chimneypieces and doors brought from Charlemont House in Dublin. Ca 1864, soon after the third earl inherited, the house was radically transformed by the young 'eclectic' architect William J Barre. Murray's wings were rebuilt on a much larger scale so that they became 3 storeys high and projected on either side of the original block. The ends of the wings were treated as corner towers or pavilions and given high Mansard roofs in the French chateau manner, crowned with decorative ironwork; but in a typically Victorian way, one of these roofs was made slightly different from the other 3.
The skyline was further enlivened with pointed and pinnacled dormers, tall chimneystacks with segmental caps, and a row of steep little pediments like saw teeth along the roof cornice. There were similar but larger pediments over the downstairs windows, some of them interlocking and with tympana containing carved heads representing members of the Charlemont family, their ancestors and several of the leading political personages of the day.
Barre's exterior ornamentation of his new wings defies description; his biographer, writing 1868, a year after his untimely death, describes it as 'the very extensive use of Classic and Gothic detail indiscrminately, an immediate connection with each other'. All this ornament was confined to the wings, the original block remaining much as Murray had left it; except for the addition of a porch, not centrally placed, on one of its fronts; the entrance having been moved here from the wing.
The whole effect was spectacular, if somewhat reminiscent of the Grand Hotel at a fashionable Victorian resort. Both Roxborough and Charlemont Fort were burnt in 1922.
Motorists passing through the village of Moy can stop in Charlemont at the junction to Portadown and see the cast-iron gate and screen set up in the 19th century to provide the grand entrance to the Castle. The richly modelled metalwork is thought by some to have been the work of the firm of the celebrated Dublin iron-founder Richard Turner, best known for his conservatories in Dublin, Belfast and Kew Gardens. 200 yards further along towards Armagh, right on the corner, one can still see the gates and ruins of the gate house to the Fort.