A SHROPSHIRE house threatened by subsidence was recently saved from demolition when contractor Van Elle used its Hoopsafe beam to enable it to be jacked back to a level position.
Insurance loss adjuster Cunningham Lindsey approached Van Elle to see if jacking the Ludlow property back to an acceptable level could spare it from destruction.
Trial pits dug outside the house and diamond cores taken inside showed the house had been built on an 800mm thick, lightly reinforced concrete raft.The minimal steel in the raft had performed well though, and the superstructure showed few signs of distress or cracking except at windows and doors.
But Van Elle decided the raft was too weak to support jacking so it installed a post-tensioned Hoopsafe beam in a trench dug around the outside the house, fixed to the raft using resin-bonded steel bars.
Polystyrene pockets were cast into the new reinforced concrete beam so the 220mm diameter steel cased driven piles could be installed through it. Internally, the raft was cored through so that 150mm piles could also be used.
After curing, the piles were trimmed so the house could be lifted using 50t hydraulic jacks.
It went from 175mm out of level to +/-5mm over a diagonal corner-to-corner distance of 13m, which Van Elle claims is more accurate than new-build tolerances.