Big Foot rises to challenge of new plant on old roof
Blezard Design & Consult of Preston was recently faced with the challenge of supporting new air-handling units and air-conditioning equipment on the aging flat roof of University Dental Hospital, Manchester. Over time the roof had been used for siting external building-services equipment and become littered with numerous pieces of plant, equipment and associated services. Being a medical facility any decommissioning of the various equipment to undertake roof works would prove hugely disruptive and extremely costly.
The roof bears all the scars of old concrete plinths, flagstones, rusting steel beams and gantries. Earlier design considerations had ultimately proved unworkable because of the large number of roof obstacles and the restricted roof space and programme of works.
It was therefore necessary to devise a system to support a new 2000 kg AHU amongst the existing equipment and obstructions. Ramped safe-access platforms were also required for future access and on-going inspection and maintenance. Consideration had also to be given to the AHU and its freestanding support frame remaining stable in high winds until the assembly benefited from the additional mass of the platforms, which could only follow later.
Big Foot Systems devised an integrated design solution of non-slip integrated modular AHU and AC unit supports with associated GRP ramps and platform access for the larger AHU to be supported independently of its associated access platform, fitting in with the programme of works programme. Analysis of wind loadings proved that the partially installed assembly would remain stable and safe in the event of any high wind loads over the construction programme.
Big Foot’s specifications manager Mike Smith comments: ‘the initial design concept looked pretty straightforward on paper but as is sometimes the case, the reality often proves more challenging. Right from the off we had to consider how to make it as easy as possible for the contractors to access the roof areas; clearly we had to go with the modular system having manageable component sizes.
‘Our technical team provided support and technical assessments for approval by the consultants to highlight some of the potential difficulties faced on site by subcontractors. Hitting critical target heights around door cills and window ledges, and achieving critical angles to span two access ramps proved especially difficult because of the limited roof space.
‘Regarding the condition of the roof and the likelihood of roof repairs being needed sometime in the near future, consideration was given to roofers needing to gain access around the services equipment and access walkways to undertake repairs or possibly even renew the roof completely. During the design process we did everything possible to allow for the easy removal of individual platform anti-slip sections and also individual feet and adjustable legs should roofing contractors ever want to gain access to the weatherproofing membrane.’
Paul Birley, project engineer with contractor T. Jolly Services Ltd, comments: The original design solution was workable but required specialist input to overcome the various issues of installing new plant and services to an existing building. Our procurement department introduced Big Foot Systems as our specialist. With close collaboration between the construction team, specialist and site operatives we have achieved a solution that meets the project requirements and maintenance issues.’
