21 Main Street, Mochrum

21 Main Street in Mochrum is an earlier 19th-century cottage that is a single storey with an attic and features three bays. It is part of a terrace and constructed with Aberdeen bond cherry-caulked masonry, using finely hewn coursed blocks in light grey shades with whinstone pinning. The building has granite lintels, cills, and rybats, along with a rendered base course.

On the east elevation facing Main Street, there is a doorway at the center with a boarded door and a letterbox fanlight, accessed by several shallow granite steps. Windows are located in the outer bays, and there are gabled dormer windows with side lights above these bays. A modern box dormer window is situated above the center bay.

The south elevation is adjoined to No 19 Main Street, while the north elevation is adjoined to No 23 Main Street. The cottage features 4-pane glazing in sash and case windows, with modern glazing in the dormer windows. The mutual skews are coped, with granite on the south side and rendered on the north. There are broad rendered mutual stacks and a roof covered with small purple slates, which has been raised on the left side to accommodate a slightly higher extension at the rear.