Palm House, National Botanic Gardens

This prestigious project involved the faithful restoration of the Palm House at the Botanic Gardens in Dublin.  The present large Palm House is the last remaining system designed glasshouse in Ireland dating from 1884.  From initial investigations in 1999, it was proved that the majority of metal work was wrought iron with the main columns and some decorative brackets being of grey cast iron.  O’Connor Sutton Cronin completed a measured survey of the existing structure and a detailed Method Statement for the dismantling and reconstruction of the Palm House was put in place.

O’Connor Sutton Cronin compiled a detailed member list which included some 7,300 timber and steel members giving the exact profile of each member together with their length and location.  Tests were carried out on the existing cast iron main columns within the building and it was found that the 20m tall columns were suffering from a progressive degradation of their carbon content.  This degradation was determined to have begun shortly after the casting of the columns in 1883.  It was concluded that this may have occurred due to poor quality control at the time of the original casting.  It should be noted that this gradual degrade is impossible to stop and therefore it was concluded that new cast iron columns would be required with the old columns providing the cast shape for the moulds for the new columns.

It was found from analysis that some of the structural members were tight on design stress capabilities for the required loading but also that some were far too slender and deflected considerably under the required wind loading.  The existing section sizes were replaced as per the original but where required were reinforced using stainless steel flat and angle sections.  The structure was approved and design was carried out to SCI Publication “Appraisal of Existing Iron and Steel Buildings” and CIRIA Report No. 111 “ Structural Renovation of Traditional Buildings”.

Construction began in March 2002 and the restored building was officially re-opened to the public in March 2004.