In 2007 serious sagging failure was found in some of the precast concrete slab units over the plantroom roof at London-Heathrow hotel. Further detailed survey identified that the original construction of autoclaved lightweight and wire reinforced slab units had suffered long term progressive bond failure of the reinforcement with loss of concrete cover.
Various repair solutions were considered which would avoid disruption to the essential equipment in the plant room and any risk to services to the hotel.
An approved scheme was developed and Ivor Parnham Building Services were appointed to work with the design team to install a grid of steel beams above the plant room roof supported on stub posts positioned over the lower columns.
Hanger rods were then fitted through drilled holes in the failed slabs connected to short lengths of steel channel cradles drawn tight to the underside of the slab and clamped to the steel grid at regular intervals.
The new beam support grid was finally covered in sheet metal roofing to falls and a rainwater collection system.