Although the architect of the Palm House at Bicton is not recorded, the genius behind the Palm House’s design is almost certainly John Claudius Loudon, in whose book, Greenhouse Companion, several similar designs appear. He had been experimenting with the building of glass domes and half domes since 1815 and invariably used the London firm of W & D Bailey to construct them. In 1818 he sold them the rights to his designs and the use of the wrought iron sash bar he had developed.
What causes such wonderment on entering is the fact that the whole central dome is completely unsupported. Loudon himself was proud. “It is worthy of remark”, he said, “that there were no rafters or principal ribs for strengthening the roof besides the common wrought iron sash bar.” In consequence the dome resembles a gigantic glittering spiders web suspended across the sky.
The whole building is held together with pressure alone and only became a stable structure when the glass was fitted in. The panes overlap each other like fish scales and each one is hand moulded thicker at the edges than in the middle. Thus the rain is deflected from the iron ribs.
At the time it was built, glass manufacturers charged their customers by surface area but were taxed themselves by the weight of the glass. For that reason they made the thinnest glass possible, large pieces of which were extremely fragile. To use small panes for the palm house at Bicton was a practical solution. It also meant that the structure would be curved, without the panes themselves being curved.