Merthyr Mawr House

Merthyr Mawr House is a late-Georgian house of two storeys and five by three bays, with a lower service block on the east side. The main building is constructed of ashlar limestone under a hipped slate roof with wide bracketed eaves and stone ridge stacks.

The symmetrical entrance front faces north and spans five bays. The outer bays are brought forward slightly, and the lower-storey windows are set higher than usual. The windows comprise small-paned tripartite sashes to the outer and central bays, with plain sashes to the narrower bays to the right and left of centre. The centrally-placed portico has two Tuscan columns in Portland stone and a plain wooden entablature. The double doors have fixed panes with panels below, are flanked by thin fluted pilasters, and similar glazed panels, with a wide fanlight containing coloured glass above.

The west garden front is three bays, with tripartite sashes to the outer bays and a plain sash to the centre. A late-19th-century stone-paved verandah extends the full width, constructed of cast iron with two-dimensional latticed piers and a hipped roof.

The south garden front is five bays with small-pane sash windows, the outer bays brought forward slightly and wider, with tripartite sashes. At the right end is an added plumbing tower of a single bay set back, with plain sashes to the first and second floors. Below it is a single-storey projection added by Pritchard around 1855, with a sash window across the angle.

The interior of the main house includes a vestibule with a pair of Tuscan columns at the inner end dividing it from a corridor to the principal rooms. The entablature has triglyphs and a cornice with a Greek key pattern. The main stairway to the left consists of an open-well stair with cantilevered stone treads, cast iron neo-classical balusters, and a wreathed mahogany hand rail. The library on the southwest side features Ionic columns with diagonal volutes. The main rooms have marble fireplaces with moulded surrounds and panelled doors with reed-moulded surrounds.

Set back from the main house is a lower two-storey office and service block consisting of a main six-bay wing facing south, a further wing on its north side, and a cold store and laundry attached at the east end. The south-facing windows are hornless sashes, and a flat-roofed projection against the central bay is of coursed, pecked stone, open on the right side, with steps leading down to a lower walled drying ground in front of the former laundry.

The single-storey former laundry, dating from 1806 to 1809 and now converted to two holiday cottages, consists of two units—the wet end on the east side and dry end to the west—under a hipped roof with a central stone ridge stack. It has doorways right and left of centre with inserted half-lit doors flanked by paired hornless sashes, and inserted windows further right and left. At the right end is an added shed, behind which are doorways to store rooms and an added vehicle shed opening to the yard.

Behind the laundry in the yard is a cold store attached to the south wing of the service block, with a half-hipped roof and pyramidal apex ventilator, replaced windows under flat heads, and lozenge-shaped vents in the end wall. A short single-storey link on the north side of the main service wing, added by Pritchard around 1855 on an earlier boundary wall, is attached to a similar parallel two-storey six-window wing on the north side of the yard, formerly the manservants' quarters and armoury.