Measuring and Assessing Change in Conservation Areas

There is widespread evidence that the character of many conservation areas is being gradually eroded by small scale changes such as replacement plastic windows, satellite dishes and paved over front gardens. In 2003 English Heritage carried out and commissioned research in an attempt to quantify, by means of fieldwork data, the degree of change to four conservation areas and to develop a methodology that can be applied to larger and more diverse areas both in rural and urban locations. The research also considered the impact of change on these conservation areas and the pressures that may be causing the changes to take place.


The State of the Historic Environment Report (EH 2002) highlighted a widely held concern that the character of conservation areas was gradually being eroded:

"There is very limited statistical information on conservation areas and almost nothing is known about loss of character by piecemeal change, which is anecdotally considered to be the biggest threat. Whilst the proportion of conservation areas covered by Conservation Area Appraisals (Conservation area Appraisals, defining the special architectural or historic interest of conservation areas EH 1997) is useful in demonstrating commitment on the part of the local authority to understand and manage character, it does not measure what actually happens in the area".

Power of Place (EH 2000) also referred to conservation areas.

"Designation as a conservation area is intended to protect and enhance character…Too often it achieves little".

Similar concerns had been raised almost ten years earlier by the English Towns Forum. In a report entitled Townscape in Trouble (1992) evidence was given of a slow but steady loss of character and significance that had justified the designation of many areas.

Pilot study

In January 2003 English Heritage undertook a pilot study which involved a house by house survey (363 houses) of the publicly visible elevations and front boundaries of a relatively cohesive single period inter-war development in west London. This was designated a conservation area in 1969 with an Article 4 direction added in 1975.

Research study

Later in June 2003 English Heritage commissioned consultant architect/planners 'The Conservation Studio' to measure change in three further conservation areas, two in London and one in Cumbria. In addition to this, two non-designated control areas were also surveyed which had broadly similar historic qualities to the main survey areas.

In Heritage Counts 2003 (The State of England's Historic Environment, EH 2003) English Heritage reported on the first stage of the research, a survey of over a thousand properties. The survey showed that all of the properties in the conservation areas sampled had experienced change to one or more of the elements surveyed. In total, the research showed that 59% of houses had replacement windows, 54% had different front doors, 37% showed a change in roof materials. Some 21% of the houses had walls that had been painted or rendered in a style that varied from the style that justified the designation of the area. However, there were significant variations between the four conservation areas.

The research has measured change against the original design of the properties rather than against their condition at the point when the area was designated as a conservation area. It can therefore be difficult sometimes to judge whether the changes had taken place before or after the conservation area achieved its designation. It is also difficult to deduce the rate at which changes had taken place.
The intention of the research was also to establish a baseline against which the rate of current and future change could be measured.

Additional Information

  • Publication Status: Completed


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