21 Gelli-deg

21 Gelli-deg is a cottage in a terraced row that has been significantly altered. The row includes an 18th-century three-bay house with a small service range set back to the right, primarily associated with No 15, while the left bay of the house is part of No 16. There are also six added cottages in two blocks, which now include the remainder of No 16, No 17, No 19, and No 21.

The upper row of three cottages is painted and rendered, featuring imitation slates and eaves that match, but with a higher ridge line than the row to the right. Nos 19 and 20, the latter now part of No 21, were originally a mirrored pair with end stacks, and No 21 is slightly larger, sharing a stack with No 20. The chimney between Nos 20 and 21 has been removed. The mirrored pair of cottages had doors leading to the inner bays and windows on each floor to the outer bay, but the door to No 20 is no longer present. The openings on the first floor of No 20 have been widened. The left end cottage, originally No 21, features 20th-century windows on the right and a 20th-century door on the left, both of which have been widened. The rear includes a 20th-century wide window on the upper floor to the left of the original No 20, along with three ground floor windows: one broad opening to No 20 and two smaller ones to the right, which may be original openings, all fitted with plastic.

The interior was not available for inspection. Original Nos 20 and 21 were surveyed in 1988 and were found to contain oak trusses with collars that had been raised when the upper rooms were ceiled. The trusses rested on seating blocks, and the roof was believed to have been stone-tiled. Each house had a ground floor layout consisting of a kitchen, sleeping room, and pantry, along with a single upper room. There were quarter-turn timber stairs with a cupboard beneath and a handrail at the top located in the front corners. The floor joists were cross-axial, and the ground floors were laid with flagstones.