Conservation compendium. Part 17: Filler-joist floors – development, capacity and typical defects

Historic buildings and structures, like any other, move to some degree, whether due to thermal effects, changes in moisture levels in the structural fabric, influences on the founding subsoil, or environmental forces. The key question for the conservation engineer is to determine whether the movement is progressive and presents a risk to the structure. This article introduces engineers to the various techniques available to monitor movement in historic structures, from simple manual techniques which are less commonly used today, to sophisticated electronic systems. The form of monitoring will depend on the nature of the assumed movement, the funds available, and the possible consequences if the movement is progressive.

This article focuses on the phenomenon of 'bond timbers', which were commonly built into masonry walls from the late 17th to the early 19th century. Guidance is offered to engineers who may encounter these when working on an existing building.

Replacement of stone on historic buildings may be required for numerous reasons. These include age-related decay and weathering, poor workmanship in terms of material choice or setting, defective fixings, and structural failure. The main aim, in assessment, will be to retain the historic fabric where practical. However, the decision to replace will depend to a great extent on having a clear understanding of the significance of the stone, both individually and within the context of the element that it is part of, its predicted life or durability and its cost.