Glasshouses and conservatories

The period from 1815 to 1835 heralded a new era in architectural design characterised by the iron skeleton and glass skin, used for glasshouses, and conservatories, led by J.C. Loudon, Joseph Paxton and Richard Turner.

The period from 1815 to 1835 saw an increasing number of structures which married together iron and glass. Indeed this was a new era in architectural design characterised by the iron skeleton and glass skin. These developments began in the exciting new glasshouse and conservatory buildings in Britain and France; but this trend was to lead to the incorporation of lightweight cladding to iron and steel structures in later buildings, notably the railway shed. In Britain three designers of glasshouses and conservatories stand out from the rest: J.C. Loudon, Joseph Paxton and Richard Turner.

Examples of their work include the glasshouse at Bretton Hall, the Palm House at Kew, and Crystal Palace.

Loudon's glasshouse at Bretton Hall, Yorkshire (1827) used light, curved, wrought iron structural glazing bars which are shown on the original drawings to be forming a dome spanning over 16m. Loudon reported that the structure used no rafters or principal ribs and "the slightest wind put the whole thing in motion"; but when the glazing was in place the structure became quite firm. Clearly the iron and glass were acting together structurally to form what we would now call a stressed-skin or membrane structure.

Turner (and Burton)'s Palm House at Kew (1844-8) incorporated wrought iron arches, with a maximum clear span of 15.2m.

Paxton's Crystal Palace (1851), with wrought iron trussed beams spanning up to 22m, along with the buildings of Turner and Burton, represent climaxes in the design of glasshouses and conservatories in Britain.

Two noteworthy early French buildings of this genre are the Galerie d'Orleans at the Palais Royal, and the Conservatory of the Jardin des Plantes.

Fontaine used wrought iron arches clad in glass to create the roof of the Galerie d'Orleans at the Palais Royal in Paris, which was built between 1829 and 1831 as a "gathering place for elegant society". This was an impressive building which was emulated in many later exhibition halls and galleries. However the first French building consisting solely of an iron frame with glass covering was the Conservatory of the Jardin des Plantes, built by Rouhault in 1833 for the botanical gardens in Paris. The form of the building is two quarter section barrel vaults giving a total enclosed volume of 9000 cubic metres. It is interesting to note that the original proposal for this scheme was even more ambitious than that built: the alternative scheme entailed covering the entire Botanical Gardens with a demountable glass and iron structure which was to be removed during the summer. This structure would have predated Crystal Palace by 18 years.

Glass as a lightweight cladding material was clearly not suitable for all building types, and corrugated iron was developed, but the success of this new cladding material was far from immediate.

Many of the nineteenth century conservatory and glasshouse structures were dramatic and ethereal. They showed that the conjunction of glass and iron could bring about new architectural solutions since not only was the glass transparent but it was lightweight compared with contemporary cladding materials and there was a consequent reduction in the size of structure required to support the glass. A second lightweight cladding material arrived in the early 1800s but in a much less dramatic fashion. Corrugated iron, the ancestor of today's profiled steel sheet, was patented in 1829. Forming iron into thin sheets with undulations to give stiffness was the idea of Henry Robinson Palmer who worked for the London Dock and Harbour Company. The corrugated sheets were manufactured by Richard Walker and were used on warehouse and storage buildings at the docks. The popularity of corrugated iron increased in the 1830s when the process of galvanising was developed which meant that not only was the material lightweight but it was also expected to be very durable. This proved not to be the case and by the 1860s it had become discredited and there was a return to boarding and slates as preferred cladding materials for some years.