May 9 - Two pioneers in modular concepts of different kinds combined to install bedrooms at the citizenM Tower of London Hotel, in the UK.

Below-the-hook equipment manufacturer Modulift, a specialist provider of modular spreader beams, supplied rigging equipment to Polcom Modular for the installation of 260 pre-fabricated structural modular bedrooms at the iconic riverside newbuild.

Modular construction is fast becoming a building method of choice for organisations looking for rapid project completion, assured quality standards and minimal impact on the environment or the local area, said Ben Paget, structural director at Polcom, which was contracted to design, manufacture, supply and install the bedrooms over an 11-week period, all at night.

The modules had bespoke lifting eyes integrated into the structural framing that were utilised by the rigging team. Each bedroom-corridor module weighed approximately 8 tonnes, while the heavier bedroom-corridor-bedroom modules were around 12.5 tonnes.

Modulift provided standard MOD 24 and MOD 50 spreader beams, which offer 24-tonne capacity at 5 m (17 ft) and 50-tonne capacity at 8 m (26 ft) respectively, as well as slings and shackles, which were used in either single or one-over-two configuration depending on the lifting points on the modules; some were four-point lifts and others eight-point. Below-the-hook equipment amounted up to 1.25 tonnes in weight for each lift.

Polcom utilised a tower crane leased by Balfour Beatty, the major contractor, which was already onsite for other lifts related to the construction project. Paget explained that as the crane was sourced prior to completion of the module design, limited height was available for the top floor bedrooms.

He added: "We had to modify the top floor lift with shortened chains and tighter angles to accommodate the final lifts. The module centres of gravity were not quite central and we had to manually compensate some of them with sandbags. Modulift's design service was critical to successful delivery of the project, giving us access to high quality drawings, specifications and expertise, particularly beneficial in offsetting the centre of gravity positions during design of the lifting frames."

During the day, spreader beams and lifting equipment was stored in a purpose-built cage that slotted onto the top of a module, located by the lifting eyes. Polcom moved the cage up each time work started on a new floor level.

Prior to installation the modules were transported from Poland to London Thamesport, where they were placed in storage. Most could be moved under normal transport restrictions but the widest had to be accompanied by special escorts. The entire modular installation crew consisted of between six and ten people, involved in onsite bolting of the modules, as well as rigging and traffic marshalling.

Paget concluded: "Our modular system is designed bespoke to every project. Size and shape varies according to the architecture. Where possible we limit the overall width, length and height to standard transportation limits to avoid extra costs, but this is not always possible."

Polcom originally tested the rig in a one-over-two-over-four configuration but height restrictions onsite meant it had to proceed with either single or one-over-two configurations.