The online resource for the historic environment

3.07 Structure

To assist your understanding of this Unit see BS 7913: 2013:
Section 5: "Using significance as a framework for managing the historic environment"
Section 6: "Significance as part of operational care and other interventions"

“Unless the structure of the building is sound, its architectural and artistic glories are bound to perish.”
Beckman (1994) Structural Aspects of Building Conservation

No amount of repair work to the fabric will have much meaning if the support frame or structure is in distress through decay and at risk of potential failure. All investigative processes to maintain an asset must, of necessity, involve checks on the condition and stability of the structural method adopted.

Some buildings such as timber-framed structures have their frame expressed externally others such as steel framed and clad buildings may not (framed construction). Buildings such as those constructed of masonry may have the structural ‘frame’ inherent within the walls, which also provides the ‘cladding’ (load bearing walls).

Identify another form of construction where the ‘frame’ also provides some of the ‘cladding’

You may wish to consider a 20th century method of construction in response to this question.

In concealed frame buildings the external cladding may present as a barrier to proper investigation of condition. In these situations the use of advanced technology may be necessary to properly identify defects and make recommendations without damaging the fabric of the building. Only after such investigation will you be able to make judgements and recommendations about remedial intervention.

How might mathematical tiles give a false impression about the true nature of an original structure.

You may wish to consider why such historical interventions were adopted, how this has defined historical change and may also define (by hind sight) contemporary re-evaluation, and how your interpretation of it might be subjective unless you clearly understand the reasons why a structure takes the form that it does.

“…Let us always beware of the uncertainties of private judgement, remembering that what to us may be without merit may well prove to posterity… of considerable value.”
Osbert Lancaster (1976)

Some early forms of structure were built when detailed understanding of structures was less advanced than it is today. Many early structures have collapsed or are in danger of collapse because of structural inadequacies. Improperly formed foundations possibly being one of the main causes of failure. Many historic structures founded on poor ground, or with inadequate regard being given to load spread, demonstrate damage to both structure and fabric that poses a serious threat to longevity.

An example of this lack of understanding may be demonstrated by the major problems resulting in potential for collapse at Winchester Cathedral. The 11th century structure was founded on very marshy ground. The original foundations were (effectively) formed using a ‘raft’ of intersecting/crossing Birch logs with the hopeful result of ‘floating’ the structure above the boggy and peaty ground. One of the largest stone structures of its day the potential for catastrophic failure was inevitable with such poor foundations. Historic records suggest that throughout its life the cathedral was beset with structural problems. In the early 15th century the tower above the crossing collapsed. The structure was a constant source of concern in respect of its stability until the late 19th century when it was recorded as being in a state of imminent collapse. It was in the very early years of the 20th century that underpinning of the whole cathedral was undertaken; famously involving the diver William Walker who, under water, placed thousands of bags of cement below the walls to replace the inadequate Birch log foundations and, via this underpinning, place the foundations in direct contact with a more suitable bearing strata at lower level.

The analysis and investigation of how such work at Winchester might be carried out involved a great deal of investigation to: a. identify the cause of or reasons for the failure and, b. to devise an appropriate method of intervention to stabilise the building. Without such investigation and analysis works of repair might have been inappropriately decided upon and the problems may not have been solved. This demonstrates the importance of properly structured investigation procedures and properly analysed response to problems.

Originally planned foundation stabilisation works was based on pumping out the excavations using steam driven pumps. It became apparent, during early pumping that that method of dewatering was in danger of creating more problems of collapse. It was at that point the diver method of executing the very necessary underpinning was decided upon. This to demonstrate the principle that even with the best planned intervention strategy, circumstance and unforeseen eventuality can result in the need to maintain a flexible ideology and method of approach, and sometimes, to be able to think very quickly.

“In the course of work on ancient buildings, points difficult to decide and needing instant decisions constantly arise.”
Powys, A. R. (1926)

You should be able to demonstrate ability to investigate a structure and determine best and least invasive methods of rectifying faults inherent in a structure.

Part of the process of investigation and analysis of structural defects will involve your assessment of how the defect is affecting the structure and what your prognosis is of its likely long-term effects. Some structural defects may not pose an immediate threat and do not require an immediate response. In conservation terms it is sometimes better to do nothing or only as much as is necessary to slow the process of change.

You should be able to demonstrate your ability to make sound judgements about intervention that not only identifies structural defects, but also best methods of dealing with the defect, including, analysis of its potential for damage both short and longer term and thence formulating an appropriate conservation strategy.

You should, within your evidence portfolio, provide details of your knowledge of the general principles of structures together with an ability to identify structural defects and their causes. You should be able to assess the impact of such defects and propose a methodology for intervention best suited to rectification of the defects and to maintain authenticity of the structure. Such intervention should subsume the main principles of conservation principle as previously defined.