Page 38 - The Building Conservation Directory 2013

3 8 t h e b u i l d i n g c o n s e r vat i o n d i r e c t o r y 2 0 1 3 T w e n t i e t h a N N i v e r s a r y e d i t i o n
1
Professional services
corrugated iron is repaired whenever possible.
There are several appropriate techniques.
Where there has been a total failure of
the paint system, this should be taken back
to sound metal. This can be achieved in situ
by using a combination of hand tools and
the application of a suitable chemical paint
stripper. If the CI sheets are to be removed
from the building a wet blast system may be
useful for removing large areas of paint. This
approach has the advantage of eliminating any
toxic dust where lead paints have been used.
Localised areas of damaged paint should be
rubbed back (using a wet abrasive for the same
reason) and repainted.
If the metal has started to corrode, areas
of light rusting can be removed with wire
brushes or abrasive papers and any remaining
rust treated with a rust converter. More
serious corrosion can be removed by carefully
controlled low pressure wet or dry blasting
or by the application of an acid gel, although
these techniques are best carried out in a
controlled environment.
Where there has been extensive corrosion,
these areas can be repaired by welding in new
sections of CI, ideally cut from a sacrificial
sheet salvaged from the same building. This
approach requires that one or more sheets
will probably need to be replaced but ensures
that the material used in the repair is totally
compatible. When new sheets are required to
make up any shortfall these should be an exact
match in size, weight and profile, and the
type of fixings and method used to attach the
sheets should also match the original.
Maintenance
CI buildings require only basic measures
to ensure their long term survival, but as
many are left unoccupied for long periods it
is important to ensure that regular planned
maintenance is carried out.
Organic or other types of debris left lying
on a roof creates areas where moisture can
become trapped. Steeply pitched roofs tend
to be self-clearing, shallower pitches should
be inspected and cleared on a regular basis.
Similarly, gutters, downpipes and gullies
should also be checked to ensure they are
working properly.
Many prefabricated buildings have large
voids or undercrofts beneath the floor and
it is important to check that air bricks or
other openings are kept clear to enable the
ventilation of these spaces.
Arguably the most important task is to
ensure that all the exterior paintwork is kept
in good order. Localised failures, especially
in external joinery, can allow water to
penetrate into the structural frame and lead
to corrosion of the corrugated iron inside
the wall cavity. Many modern paints now
have excellent anti-corrosion properties and
long renewal cycles. However, these need
to be considered carefully in light of any
important historic decorative schemes.
Adapting CI buildings for
alternative uses
Increasing pressure to develop existing sites,
climate change legislation, and changing
economic and social trends mean more
CI buildings are threatened with demolition
or inappropriate alteration. With a little
imagination and the political will, many
of these buildings could provide viable
and sustainable spaces for a wide range of
alternative uses. Large numbers of CI aircraft
hangars are being used for storage, light
engineering, transport and leisure purposes.
The London Science Museum, for example,
has successfully used a former RAF hangar to
house its large object collection.
The exteriors of CI buildings are sensitive
to change and if they are to retain their special
qualities and visual identity all external
elements normally need to be retained.
Internal spaces are usually less sensitive to
change and provide a flexible space capable of
sub-division. Many smaller prefabricated CI
buildings offer opportunities for adaptation to
residential, business, leisure and community
uses. If done with sensitivity and imagination,
redundant mission rooms, chapels, hospitals
and other CI structures can be adapted to
provide energy-efficient, sustainable buildings
that respond to the increasing pressure to
conserve energy.
Most small prefabricated buildings are
built on a simple modular timber framework
that provides a clear cavity between the inner
and outer cladding of around four inches.
Inserting rigid or other forms of insulation
into this cavity can be achieved with little or
no visual impact and can enable the thermal
performance of the building to comply with
current building codes.
Obtaining insurance and finance for
CI buildings adapted for residential and
other uses can be challenging but is possible
through a number of companies which
specialise in buildings of non-standard
construction. Typically, insurance premiums
will be higher and the number of risks covered
will be limited. Mortgage companies are also
likely to require detailed surveys and ask for
larger deposits.
The future
With improved understanding and a
greater awareness and interest in these
once ubiquitous buildings, the future looks
brighter for the relatively few remaining
examples. Buildings that until recently
were often considered eyesores and unfit
for purpose are now being rescued as
their contribution to our architectural
landscape is more widely appreciated.
Recommended Reading
J Davies, Galvanized Iron: Its Manufacture
and Uses, E & FN Spon, London, 1899
G Herbert, Pioneers of Prefabrication, Johns
Hopkins University Press, London, 1978
A Mornement and S Holloway, Corrugated
Iron: Building on the Frontier, Francis
Lincoln, London, 2007
I Smith, Tin Tabernacles: Corrugated Iron
Mission Halls, Churches and Chapels
of Britain, Camrose Organisation,
Pembroke, 2004
B Walker, Historic Scotland, Technical
Advice Note – Corrugated Iron and other
Ferrous Cladding, Historic Scotland,
Edinburgh, 2004
Tim Nicholson MScCHE is a historic
building consultant with Nicholson Price
Associates (see page 41). Email info@
npaheritage.co.uk
This semi-derelict estate church manufactured by Boulton & Paul Ltd during the 19th century demonstrates how
some corrugated iron roofs imitated roof structures of a much grander status.
Part of a former historic iron works: notice the distinctive
pattern of corrosion to the roof covering, which
corresponds with the fixing points and sheet overlaps.