Rubble, coursed rubble and ashlar masonry

Random rubble masonry

Stones of irregular shape and size, as obtained from the quarry, are laid without courses; small stones fill the gaps.

• Uncoursed random rubble: stones used as they come, roughly shaped with a hammer; bond stones (through stones) every 1.5 m² of wall.
• Coursed random rubble: work is levelled at about every 300-350 mm height to form rough courses.
• Joints are irregular, mortar 1:6 (cement-sand) or mud/lime mortar; thickness of wall at least 400 mm.
• Cheap, suitable for foundations, boundary and retaining walls in hilly areas of Nepal.

   ____ ___ _____ __
  /    \   \     \  \   irregular stones,
 /__ ___\___\_____\__\  no regular courses
 \  /   /  / \    /
  \/___/__/___\__/

Coursed rubble masonry

Stones are roughly dressed and laid in courses of equal height in each course; height of courses may differ from course to course.

• First sort: face stones squared with hammer, courses 150-300 mm high, joints thin (about 10 mm); all courses levelled.
• Second sort: stones roughly dressed, joints thicker; courses not so regular.
• Third sort: stones hammer-dressed lightly, used for ordinary walls.
• Bond stones 1 per m² of face and quoin stones at corners; stronger and neater than random rubble.

 +------+---+-----+--+   course 1 (h1)
 +--+-------+----+---+   course 2 (h2)
 +-----+-----+--+-----+   course 3 (h3)

Ashlar masonry

Stones are finely dressed to exact rectangular blocks with fine joints (3-6 mm) and laid in regular courses; it is the best and costliest stone masonry.

• Ashlar fine: every face chisel-dressed, joints 3 mm; used for monumental buildings.
• Ashlar rough-tooled: faces roughly tooled, joints up to 6 mm.
• Ashlar rock-faced (quarry-faced): face left rough with a dressed margin around.
• Ashlar chamfered: edges chamfered at 45 degrees, giving a V-joint.
• Block-in-course: blocks of equal height dressed; backing of rubble.

 +------+------+------+
 +---+------+------+--+   regular courses,
 +------+------+------+   thin joints