A £34M project at the world’s largest Victorian glasshouse set in Kew Gardens has reached a major milestone, after the restoration of the roof of Temperate House’s north building was completed.
Temperate House took 40 years to build and work was briefly halted when the project ran £19,000 over budget in 1860. The structure was placed on the Heritage at Risk register in 2012 after corrosion damage was discovered in the structural frame, made of steel and iron.
Since September 2014 contractor ISG has removed and restored 69,151 individual steel and iron sections of the Grade I-listed building offsite. During the work, a water-tight sheet measuring 73m has protected the glasshouse and trees underneath, and shielded the repairs from view.
But the first section of the covering has been removed from Temperate House’s north building, revealing the restored roof for the first time.
“There’s thousands of visitors coming here [Kew Gardens] every day; fairly soon they’ll be able to see the whole thing,” said ISG project director Shane Mason.
Workers will finish at the site in December, giving the Kew Gardens horticultural team time to bed in the rare plants before it is officially unveiled to the public in May 2018.
A previous three-year restoration scheme in the 1970s replaced several aspects of the original structure. These including the glass; however, most of the steel and cast iron metal work was Victorian.
All 69,151 parts were individually tagged and logged before being taken offsite and restored.
“Control has been tight and very well managed I would say,” said Mason.
“We’ve had a database which has maintained a register of where every single piece of the building is at any one time, so whether it was offsite, whether it was in our storage area, whether it was onsite or whether it had been fixed on the building. An awful lot of it has now been fixed onto the building; we’ve still got that register running.”
Existing layers of paint were stripped using an ultra-high pressure wash, which revealed areas of porosity, or rust, in some of the metalwork. This needed to be repaired before four coats of paint were applied, designed to last 25 years.
Additional restoration work was carried out onsite: experts in lead work were required, while joiners replaced rotten areas of woodwork with exact replicas which will be painted over.
“No-one will ever know [the woodwork has been restored] but it’s nice to know that it has been done properly,” said Mason.
Work to dismantle the next tent, covering the house’s south block, will start on 23 May.