Kölner Dom©
Structural stability & load bearing capacity

Filling hollow spaces and improving the load-bearing capacity of historical constructions

The masonry constructed building is a tradition that goes back many centuries. In the past, brickwork was built by craftsmen and women; the stone format and wall thickness depended on the estimated loads. Today, information about the load bearing capacity of an historical building is very important for securing and modifying old building substance.

Load relocations and/or increases within the masonry can be caused by damage, restoration or securing work or changes of use, and create new damage. Load-bearing parts of historical buildings, like walls and columns, frequently comprise two-shell natural stone or brick masonry work. Whilst the outer ‘shell’ is bricked normally, there is usually a ‘filling’ of stone chips and a high percentage of mortar on the inside of these parts. Above and beyond the strength and deformation properties of stone and mortar, the load-bearing behaviour is also influenced by many other parameters.

These include:

  • Masonry structure (single / multiple layers)
  • Stone size
  • Masonry type
  • Execution quality
  • Spread of stone and mortar quality

In most cases, hollow spaces and clefts within the masonry reduce the load-bearing capacity. This means that backfilling these kinds of faults is necessary when restoring masonry. In particular, the mortars used for filling or compressing must be selected with respect to their strength, water absorption capacity and binding agent compatibility.