26 Castle Street, Rothesay, Bute

26 Castle Street is a mid-19th century, asymmetrical, two-storey, two-bay former school that has been converted for use as a church hall on the ground floor, with a single flat on the first floor. The building features random rubble sandstone with droved yellow rubble sandstone dressings. It has a raised base course, stepped hoodmoulds, and three-quarter engaged moulded stops, along with overhanging eaves. The quoins are made of droved rubble, and there are droved long and short surrounds to polished, chamfered openings, with timber mullions and chamfered cills. A later red brick addition is located at the rear.

On the north elevation, the entrance features an original timber panelled door set in a chamfered, round-arched surround in the outer right bay, accompanied by a bipartite fanlight and a bipartite window above, which is aligned with the first floor. There is a bipartite window at ground level in the left bay, with a blind single window above.

The east side elevation has three bays, each with tripartite windows at ground level and gabled tripartite windows in all bays that break the eaves at the first floor. The original diagonal-paned leaded windows are present on the north side, while leaded windows are located at ground level on the east side. The first floor features replacement tripartite plate-glass windows. The building has replacement rainwater goods, a graded grey slate roof, raised stone skews, and scrolled skewputts. There are coped apex stacks on the north and south sides, a single circular can on the north side, a corniced ridge stack on the west side, and another single circular can.

The interior has been adapted for use as a church hall on the ground floor and contains a church flat on the first floor.