Corrugated Iron Architecture
Herd Groyne Lighthouse (1881), South Shields, Tyne and Wear
(Photo: Emma Joice)
Loathe it or love it, corrugated iron (CI) has woven its way into our cultural landscape. Its unique qualities have captured the imagination of engineers, designers and ordinary people for almost 180 years, resulting in a diverse architectural legacy that has touched the lives of millions around the globe.
The significance of CI is now recognised particularly in countries such as Australia and Iceland where it is commonly found in both historic and modern contexts. In contrast, the UK has been comparatively slow to accept the cultural value of CI, many observers considering it subordinate to more permanent and traditional materials. Considerable numbers of historic CI structures still survive, but many of these are under increasing threat from neglect, development pressures and changing social and economic conditions.
This article explores the development of corrugated iron and considers the problems and opportunities for conserving existing historic structures and adapting them for economically viable and sustainable alternative uses.
HISTORY AND DEVELOPMENT
Henry Robinson Palmer, who recognised its potential for covering wide span roofs, patented corrugated iron in 1829. The following year, Palmer, who was an engineer and architect with the London Dock Company, built a large shed at the docks roofed entirely of self-supporting corrugated iron sheets and spanning 40 feet. The use of CI quickly proliferated and notable examples from this early period include parts of Chatham Dockyard in Kent and Liverpool Lime Street Station. Eminent engineers including Isambard Kingdom Brunel embraced its unique characteristics in iconic structures such as London’s Paddington Station.
The iron building revolution was inexorable in its influence on architects, engineers and progressive members of the manufacturing community who saw the wider potential and developed a type of construction that is uniquely resonant in the collective architectural consciousness: prefabricated corrugated iron buildings.
By the 1840s the production of fully prefabricated CI buildings was established in Britain. Many of these buildings fed the requirements of colonial expansion into countries such as Australia and South Africa. The domestic market for prefabricated buildings was also growing, and as transport links improved, the pallet of locally available materials was expanded to include sheet iron. Public fascination with this new and exciting material was such that in 1845 an ‘iron palace’ built in Liverpool for export to Africa was displayed to the public, who paid a small fee to view it.
However, the public love affair with corrugated iron during the first half the 19th century does not appear to have been unanimous or unconditional. Contemporary reports suggest that some bishops were unwilling to consecrate iron churches and that the public would not tolerate it in their towns and cities.
SOCIAL AND ECONOMIC INFLUENCES
The latter half of the 19th century was characterised by increasing industrialisation and a steady migration from the country into the towns and cities. Many of these urban settlers endured difficult working and living conditions, and found comfort in religion which played an increasingly important part in people’s lives during much of the 19th century.
|Regular painting is often all that is needed to ensure that iron cladding remains in good condition. Simple features such as this decorative ridge piece require particular attention to ensure the character of the building is preserved.|
Companies such as William Cooper and Boulton & Paul helped to feed the demand for chapels, churches and Sunday schools along with many other types of CI building, which were sold in large numbers and transported across the country. Many of these religious buildings survive today as a visible reminder of the prevalence of CI buildings during the 19th and early 20th centuries.
CI AS A REPLACEMENT MATERIAL
Rural landscapes changed forever during the late 19th and early 20th centuries as corrugated iron replaced materials that had persisted in local building traditions for centuries. Thatch in particular, which had become associated with rural poverty, was often replaced or sheeted over with corrugated iron. As a consequence, local vernacular styles were partially eroded but, paradoxically, CI also extended the lives of many rural buildings.
Until the early 20th century most military structures had been permanent. However, the first world war acted as a catalyst to the development of one of the once most ubiquitous of CI buildings, the Nissen hut. Named after their designer, Captain Peter Nissen, these distinctive structures were cheap to manufacture, easy to transport and simple to erect, and they solved the huge logistical problem of housing millions of troops. Nissen huts continued in military service through both world wars and beyond.
Following the first world war, attempts were made to develop the Nissen hut design for the residential housing market but this proved to be uneconomical and only a handful were ever built. Many Nissen huts survive today and have been successfully adapted to a wide variety of uses, a testament to their versatility and robustness.
New building types proliferated in Britain during and between the two world wars. Many were associated with the newly formed RAF, but one in particular was produced on an enormous scale. At least 1½ million Anderson shelters were distributed to British households during the second world war to help protect the population from German bombing, making it possibly the most widely produced prefabricated structure ever seen in Britain and one that is deeply embedded in the memories of a generation.
|The significance of a building is not always apparent from its appearance. Stripped of its corrugated iron cladding, this early 20th-century structure forms part of a peat processing plant and is a rare survivor of an industry dating back to medieval times. The structure is Grade II* listed and a scheduled ancient monument.|
The idea that corrugated iron could have any sort of cultural significance has been slow to take hold in Britain. This has been a particular problem for the smaller prefabricated structures, many of which have been demolished.
Nevertheless, the architectural and historic significance of CI is now more widely recognised and there is a greater understanding of the less obvious attributes of these structures such as innovation in design and construction, associations with people and places, positive contribution to urban and rural landscapes, and economic value. Some examples have been given statutory protection and several have been carefully dismantled and erected at open air museums.
Despite greater awareness and understanding, however, the significance of many CI buildings remains undervalued. In some cases comparatively good but isolated examples remain quietly undiscovered, while other examples may fail to become part of the historic environment records due to difficulties in making comparative value judgements.
The threats to historic CI structures are not as obvious as those facing more mainstream buildings. Climate change legislation may lead to the loss of CI buildings as unimaginative owners, designers and planners fail to appreciate how many of these buildings can be successfully adapted to provide valuable, efficient and comfortable spaces.
|Poor maintenance can lead to the loss of important visual elements.|
Long-term vacancy and often minimal security leaves many historic CI buildings vulnerable to theft, vandalism and arson. The relatively high fire loads of CI buildings and the often secluded locations may mean that any arson attack would very quickly lead to total destruction of the building.
Many former religious buildings are located in picturesque rural locations, and although there is normally a presumption in favour of retaining existing buildings, the arguments for demolition and redevelopment can be persuasive. The same buildings are often sold subject to a number of restrictive covenants which can severely restrict their market appeal and lead to further problems associated with long term vacancy.
The single biggest threat to corrugated iron is undoubtedly neglect. Fluctuating economic fortune, the abandonment of buildings, and a failure to undertake even the most basic maintenance all precipitate the decline and, in some cases, loss of these vulnerable buildings.
Historic CI sheets were produced in a variety of lengths, widths, weights and profiles. Typically sheet sizes are 3-10 feet long and 1830 inches wide although other sizes were made to order. Profiles tend to conform to the ridge and furrow or wave pattern with an average pitch of 3-5 inches. Historically, CI sheets were produced according to the Standard Wire Gauge (SWG) system of measurement. Sheets used for roofing were typically 18 SWG (1.2mm) thick and weighed around 1.2kgs per square foot. This compares with commonly available modern sheets which weigh around 0.7kgs per square foot.
Most corrugated iron was galvanised but sheets were occasionally supplied as ‘black iron’ (ungalvanised). The quality of the metal varied along with the quality of the materials and the proficiency of the workers employed in the galvanising process. Along with other factors, this variation in quality has undoubtedly had an impact on the long term survival of corrugated iron.
Prefabricated buildings of all shapes and sizes were constructed using simple lightweight timber and metal frames to support the CI cladding. While many agricultural and industrial buildings merely required the corrugated iron to form a weather-tight shell, large numbers of CI buildings were constructed with elaborate interiors.
Most of the chapels, pavilions, mission rooms and other small prefabricated buildings that survive are constructed using a framework of 100 x 50mm (4 x 2 inch) softwood timber. Floors are usually suspended timber, with the entire building normally sitting on a masonry plinth which was built prior to the arrival of the building. Many of these buildings have surprisingly comfortable, sometimes even elaborate, interiors. Roof structures vary enormously, from simple scissor trusses to impressive arched-braced collar trusses.
|Corrosion of corrugated iron cladding is often the result of changes in ground level.|
Often thought of as an ephemeral material, corrugated iron has in many cases far exceeded its expected service life, but condition is often a reflection of the building’s use and the owner’s willingness to undertake simple but regular maintenance.
Galvanising was perfected in this country soon after CI was introduced and offered a long-lasting and economical means of preventing corrosion by applying a thin coat of zinc to the metal sheets. Ultimately this coating degrades or becomes damaged in some way allowing the unprotected metal to become exposed to the atmosphere, resulting in corrosion.
Corrosion often begins where two sheets overlap, the small gap setting up a capillary attraction which allows the joint to hold water. This can lead to an electrochemical reaction that causes the zinc coating to preferentially corrode beneath the overlapping sheets. This type of reaction can also occur in positions where fixings made from a different type of metal have been used. This process is likely to be accelerated in marine locations and areas subject to acid rain due to the increased conductivity of the electrolyte solution that connects the metals and allows the electrochemical reaction to occur.
Rapid and extensive corrosion can also be found where CI wall cladding has been partially buried due to changes in ground levels or alterations to the plinth. Most corrugated iron will have been painted at some point during its life, if this has been done regularly the incidence of serious corrosion is normally far lower.
Holes can sometimes be seen in the CI cladding where sheets have been removed or replaced and fixing bolts placed in different locations. This can lead to water ingress and accelerated corrosion around the hole. Impact damage caused by vehicles can often be seen on industrial or military buildings, and it is common to see sheets peeling away from their supporting structure where fixings have been damaged.
Large CI buildings often have iron or steel frames supporting the cladding. Metal ties, rods and brackets are also common, and where these components are concealed they are at particular risk from undetected water ingress.
The majority of small prefabricated buildings are constructed with softwood frames and a large number of other timber components. Simple maintenance is often all that is required to ensure the timber remains in good condition. Unfortunately, neglect is common and timber decay is often found in external joinery items such as windows, doors, barge boards and fascia. Unless there has been long term neglect and water ingress, the timber frames and floors are often in excellent condition.
REPAIR AND CONSERVATION
Regardless of the type or age of a structure, the principles of conservation and maintenance are largely the same. The process must start with a clear understanding of the structure gained through documentary research and physical examination and recording. The significance of the structure needs to be identified at an early stage in order to assess how any repairs, alterations or changes in use will impact on the special qualities of the building. Typically this will involve retaining the visual characteristics and as much of the historic building fabric as possible.
|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|
Clearly it is important that any historic 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.
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
|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.|
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.
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.
J Davies, Galvanized Iron: Its Manufacture and Uses, E & FN Spon, London, 1899
G Herbert, Pioneers of Prefabrication, Johns Hopkins University Press, London, 1978
DS Mitchell, INFORM – Care and Maintenance of Corrugated Iron, Historic Scotland, Edinburgh, 2008
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, Technical Advice Note 29 – Corrugated Iron and other Ferrous Metal Cladding, Historic Scotland, Edinburgh, 2004