Conservation Principles, Policies and Guidance - English Heritage

MANAGING CHANGE TO SIGNIFICANT PLACES
101 However, places should not be rendered incapable of a sustainable use simply
because of a reluctance to make modest, but irreversible, changes. It is also
unreasonable to take the idea of reversibility to the point that intervention
in significant places diminishes their aesthetic values by appearing contrived,
awkward or ugly, in order to ensure that it can be undone. Unless of very
short duration, crude and intrusive changes are certainly not justifiable
simply because they are theoretically temporary or reversible, for they
risk becoming permanent.
Compare options and make the decision
102 Ideally, proposed changes will cause no harm to any of the values of the place,
and the right decision will be obvious. In practice, however, there tend to be
options for achieving the objective of proposed change, each of which will
have different impacts on values. The predicted long-term or permanent
consequences of proposals (in terms of degree, and whether positive, negative
or neutral) on each of the identified heritage values of a place, and thus on
the significance of the whole, should provide the reasoned basis for a decision,
where necessary taking other interests into account.
103 Where there are options for the conservation management of change, or
reconciling conservation and other interests, ‘heritage impact assessment’
can be used to compare the predicted effects of alternative courses of action
(including taking no action) on the values of a place, in order to identify the
optimum solution. The approach can be refined by weighting different values
to reflect their relative importance for the place and its significance. Heritage
impact assessment can be particularly useful if applied at the conceptual stage
of a proposal, and refined at each successive step towards making a decision.
Apply mitigation
104 If some negative impact or loss of fabric is unavoidable, mitigation should be
considered to minimise harm. This will normally include making records and
archiving parts of significant elements, including archaeological deposits,
that will be removed or altered prior to and during the work, in accordance
with Principles 6.3 and 6.4. A high quality of design of proposed interventions
is not mitigation; it is essential in any significant place (Principle 4.6),
regardless of any unavoidable harm. Mitigation should not be confused with
compensation – non-essential benefits to other aspects of the place, or to
other heritage interests.
47