Rubble masonry

Rubble masonry, in Turkish moloz taş duvar, is a wall built from irregular stones gathered from a quarry or the site and laid in generous mortar. Often only the exposed face of each stone is roughly trimmed, and the gaps are packed with spalls and mortar. It is the most common wall type in rural architecture, in the ground floors of traditional houses, in garden and retaining walls, and in the cores of monumental buildings.

Its role in the building

Rubble walls are usually thick and draw their strength from mass. In many examples the two faces are built separately and the middle is filled with smaller stones and mortar; long through-stones tying the faces together and timber lacing at regular heights make the wall act as one. The mortar is not just filler but a bed that spreads load between the stones, so its quality and its loss directly affect how the wall performs. Many rubble walls are finished with render or faced with ashlar.

Rubble masonry in survey and restoration

• Collapsed areas, opening reveals and small probes are studied to understand the wall section.
• Washed-out joints, separating and bulging faces and rotten timber lacing are the main forms of damage.
• Consolidation favours lime-based grouts and compatible pointing mortars.

Cement renders and joints stop a rubble wall from breathing out moisture; the trapped moisture and salts then attack the stones and the original mortar. In survey drawings rubble walls are not drawn stone by stone but mapped as material and decay zones, while in a 3D model a texture produced from an orthophoto conveys the surface best.