Types of stone masonry

Stone masonry is the construction of walls with stones bonded with mortar, or sometimes laid dry. It is classified into rubble masonry and ashlar masonry.

1. Rubble masonry

Stones are undressed or roughly dressed, with irregular faces.

• Random rubble: Stones of irregular shape and size, as obtained from the quarry. Two types: uncoursed (no regular courses; cheapest) and coursed (levelled at 300 to 600 mm intervals).
• Square-snecked rubble: Roughly squared stones of different heights, with small stones (snecks) in the gaps.
• Coursed rubble (first, second, third sort): Stones roughly hammer-dressed, laid in courses of equal height. First sort: stones are dressed, course height 150 to 300 mm; the second and third sorts are less regular.
• Dry rubble: Without mortar; for boundary walls and retaining walls.
• Polygonal rubble: Stone faces dressed to irregular polygon shapes, with joints at several angles.
• Flint rubble: Built with flint stones.

2. Ashlar masonry

Stones are finely dressed, with all faces and joints chisel-dressed to uniform sizes, and laid with thin joints (3 mm).

• Ashlar fine: Very fine, with joints about 3 mm; best finish.
• Ashlar rough-tooled: Faces roughly tooled.
• Ashlar rock-faced (quarry-faced): Face left rough, with a chisel-drafted margin.
• Ashlar chamfered: Edges chamfered at 45°.
• Ashlar block-in-course: Stones squared and hammer-dressed, laid in courses of equal height (about 200 to 300 mm) with joints up to 6 mm; a grade between rubble and fine ashlar.

 Random rubble        Coursed rubble        Ashlar
  _/\_  __           |____|__|____|        |____|____|
 |  \/_|__|          |__|____|__|_|        |____|____|
 (irregular)         (courses levelled)     (fine joints)

Comparison

Typical rules: through stones at 1.5 m intervals, wall thickness at least 350 mm, and good bonding with 1:6 cement-sand or mud mortar.