Cargill Meats, Hereford

Project Overview

The client brief was to take down the roof and walls of this tired old production facility to first floor level, and construct a new storey in it's place off the first floor. This would not only improve the fabric of the building but also give the additional storey height necessary for them to create a new production line within it.

The challenges to achievethe client brief were formidable however:

  • The existing production facility on the ground floor below which runs 24 hours/day was to be kept in operation.
  • The existing concrete floor from which we would be working was of unknown strength and so nothing we put on it could exceed 500kg in each square metre of floor.
  • vehicle routes at ground level were to be kept open as normal, which would rule out many of the larger crane options which might otherwise have been utilised.

Our solution to the final point was to carry out the whole of the construction working from the first loor slab, but to do so we would have to engineer a way to limit the weight load on the floor to no more than 500kg per square metre. We opted to construct the building using two tracked 'spider' cranes supported by a wheeled mobile crane on the ground. A complex support structure was designed for the spider cranes which ensured that their weight was always transferred onto structural steel below the concrete floor, and not onto the floor itself. Whenever the cranes had to move, they would move the temporary support structure ahead of them section by section before moving onto it, a painstakingly slow but necessary process. Similarly, materials (including some substantial structural steel members) would be moved via trolleys specially designed to spread the weight and ensure it would be transferred to the steel structure below.

Had we constructed the steel superstructure all in one operation, the spider cranes would not have been able to get back to lift the roof cladding sheets on, and so we opted to clad the roof as going along, so lifting a section of steel roof structure into place, then lifting the cladding sheets onto that section before moving onto the next to repeat.

The project was completed successfully ahead of the target programme and the client's day-to-day production below continued uninterrupted.