Glasgow City Hall RETROFITTING THE GRAND HALL

Originally specified by the project’s theatre consultants Arup Acoustics, the Cablenet design had to be rigged amidst the original timber roof trusses and work integrally with the building's roof structure. The frames are supported by these trusses with their brackets straddling the bottom shard of the timber truss. In addition, no intermediate Cablenet members were to be visible from the underside.

• 10 modular grids - 10.9m x 3.3m, each slightly different to account for fluctuations in the roof timbers
• Supports a total load of 3.6 tonnes distributed over the 10 grids (360 kg per frame)
• Rigged amidst the original timber roof trusses
• No intermediate Cablenet members visible from the underside>
• Constructed from 3mm wire

The grids are engineered to work in a back-to-back fashion: the frame side members form horizontal trusses over the bottom member of the timber trusses allowing a lighter section to be used for absorbing the loadings from the tensioning of the cable assemblies. On the underside, the grids are separated by cosmetic plastered roof panels, so from the hall below it looks as if there are 30 smaller nets.

A four person team from Slingco completed the installation in two weeks.

Another reason for choosing Cablenet involved practicalities relating to the overall task of improving the room acoustics. The stage has been lowered to increase the volume of the ceiling area above, aiming to create a bigger and fuller orchestral sound, so it was essential that the grid above would work in as shallow a roof space as possible.

Neatly concealed above the grid at the stage end of the Cablenet is a series of acoustic baffles.

TENSION WIRE GRID TYPE

Modular

INSTALLATION

• Retrofit
• 10 grids - 10.9m x 3.3m

Architect

Glasgow City Council

Main contractor

HBG Construction Scotland Ltd

Theatre consultant

Arup Acoustics

From working out a suitable scheme with Ray at his Judds Farm base, developing the design to ensure an efficient manufacturing and installation method to carrying out the final inspection on the finished installation, the job’s proved to be one of the most interesting the team has worked on. Peter Downham-Clarke, Slingco