Issue 37 Spring 23 WEB - Flipbook - Page 14
Traditional
stone cleaning
for heritage facades
There are few things more rewarding than delivering a
cleaning and restoration package to a historic building in
the knowledge that the careful specialist approach will
help to ensure the preservation of the building for future
generations. Cleaning is an important and essential part
of conservation and preservation which must be carried
out without damage to the substrate, and this requires
experience.
unfortunate patterns of poor cleaning being undertaken,
most often exercised using damaging abrasive cleaning on
the wrong surfaces causing extensive damage to the building skin. Although not stone, glazed terracotta (faience)
facades have also suffered historically from ill-conceived
cleaning methods using chemicals, typically strong acids,
and harsh aggregates that resulted in serious damage to
the fire skin of the material, leaving it open to water
ingress and ongoing associated problems. Before any
programme of works are undertaken the building should
be properly surveyed and a report drawn up by a specialist,
such as Szerelmey, indicating the level of cleaning and
repairs that might be required, and also the nature of the
building fabric itself. Following on from this, and an
essential part of the pre-contract process is exemplar
sample cleaning and test panels.
So why bother cleaning a building? The answer might
seem obvious, that it improves the aesthetic and general
appearance – after all, first impressions count. This is true,
of course, but more importantly cleaning should be
undertaken as a means of preserving the fabric of the
building to ensure its longevity, and to enable vital checks
for structural problems or issues to be carried out. Surface
soiling often contains sulphates from industrial and traffic
pollution, when these mix with water (moisture in the air
and rain) they create a sulphuric acid based compound
on the surface of the facade that can lead to accelerated
decay in materials that are not acid resistant.
These exemplars assist in determining the level of clean
and the cleaning method required. This enables buildingspecific specifications to be written and a cost plan to
be drawn up. With heritage and listed properties it is
particularly important to ensure the relevant authorities
such as conservation officers have seen and agreed the
exemplars. Szerelmey have recently completed a full package of cleaning and restoration works to the exterior and
interior of Camden Town Hall, a project which involved
a number of traditional specialist cleaning processes.
The approach to cleaning any historic building or
structure should always be one of caution. It is far better
to under-clean than to over-clean and potentially damage
fragile areas. In the same vein it is equally important to
not over-saturate the stone with water which can cause
damage and staining. A number of years ago there were
Main picture, Camden Town Hall after. Inset, Camden Town Hall before
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Conservation & Heritage Journal
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