A rubble-cored wall is a heavy wall construction with a built inner and outer leaf whose very thick cavity is filled with sand, stone and rubble. The two leaves form, in effect, the sides of a box; the fill supplies mass and with it stability. The Dutch term is kistwerk, literally “box work”.
It is one of the oldest ways of producing a very thick wall with limited means: the expensive, carefully laid work sits only on the faces, while the interior is cheap material available on site.
Build-up
| Element | Function |
|---|---|
| Outer leaf | Built masonry, exposed and weather resistant |
| Inner leaf | Built masonry on the inside face |
| Fill | Sand, stone and rubble; later also mixed with mortar for cohesion |
| Through stones | Blocks set right through the fill to tie the two leaves together |
Those through stones are structurally essential: without a tie between the leaves the fill can push them outwards. Later work mixed mortar into the fill, producing something closer to a cast core that can itself transfer load.
Where you find it
- City walls and fortifications — thick walls where mass mattered more than fine workmanship; a Dutch example is the town wall of Hardenberg
- Church building — among others in Romanesque churches, such as the Sint-Martinuskerk in Bozum
- Roman construction — comparable techniques are known as opus latericium and opus incertum, where a skin of brick or irregular stone encloses a core of mortar and rubble
Points to watch in restoration
- Never simply break through — an opening in the outer leaf can let the fill run out; the core is not a bonded whole
- Washing out of the fill — leaks or rising damp can flush sand out of the core, leaving voids and causing settlement
- Inject with care — consolidation is done with lime-based grouts; too strong a cement mix creates stiffness differences and damages the historic fabric
- Moisture cannot escape — such walls are thick and dry slowly; vapour-tight finishes inside or out usually make damp problems worse
- Always have it assessed by a specialist — in listed buildings work to the masonry also requires consent
Related terms
- Masonry
- Reinforced masonry
- Brick
- Gauged mortar
- Cavity wall
- Foundation
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