Sixteen 20-tonne capacity screw jacks from Kennards Lift and Shift were part of an innovative solution to a problem encountered during building repair work at an historic Adelaide school.
Heritage Stone Restorations had to find a way to underpin the sandstone columns of the original building at Annesley College – previously Methodist Ladies College – to allow the footings to be replaced.
“The building dates back to the 1880s and, basically, the bluestone footings weren’t doing their job any longer, and there was a considerable amount of movement,” said Kim Sutherland, a director of the company which has worked on many of Adelaide’s oldest buildings.
“We had to support four arches and the ends of the verandah while we dug out underneath and put in new pier footings.
“After looking at a range of possible options, we decided there was really only one way it could be done.
“We rebated the sandstone columns with 200mm X 100mm X 8ml SHS (square hollow section) steel, which was bolted together, providing a lifting point for the screw jacks.
“It was crucial that the columns not move while they were supported because they were holding up the whole building.
“The screw jacks were tremendous. You can wind them to the precise height required and there is not the slightest slippage.
“We have faced various challenges when repairing or restoring historic buildings and other structures, but this was the first time we have had a situation like this, and we were very happy with the outcome.
“Kennards Lift & Shift has helped us out on other jobs, so we knew where to turn for the specialist equipment we needed.”
Screw jacks are designed to lift and hold heavy loads for extended periods.
The 20 tonne jack has a range of 400mm-640mm and weighs 15kg, while a 12 tonne model lifts to the same height but is half the weight. They have a four-way head which permits lever bar insertion at four angles.
Many other types of jacks can also be hired from Kennards Lift & Shift, which has hire centres in Sydney, Wollongong, Melbourne, Adelaide and Perth, and will be opening a new outlet in Queensland early in the New Year.