At roof level, the restoration efforts include dismantling and rebuilding 30 of the 34 chimneys, and replacing 140,000 roof tiles.

Removing the roof finish has afforded the opportunity to install a new pitched roof underlay. The project architects specified Proctor Air, with Mac Roofing & Contracting Ltd carrying out installation.

As an historic building, the Manchester Town Hall roof features many intricate details. The complexity of the roof forms, combined with the age and heritage value of the building fabric, means opportunities to provide modern roof ventilation are limited.

A key advantage of Proctor Air, as an air permeable low-resistance (APLR) membrane, is that it removes the need for separate roof ventilation. In fact, it provides a more uniform flow of air in the roof space than normal vents, ensuring there are no ‘dead zones’ where the complexity of the roof form could otherwise have restricted air movement.

Air permeability performance is important, but must work alongside good vapour permeability performance. With an Sd value of 0.015m and a vapour resistance of 0.075MNs/g, Proctor Air is one of the highest performing vapour permeable membranes on the market.

The “invisible story” behind preserving heritage

During the restoration carried out so far, Manchester City Council has worked to promote the “invisible story” of the project – the elements of the scheme that won’t necessarily be obvious to most people, but which help to preserve the Town Hall’s heritage.

Pitched roof underlays are a true ‘fit and forget’ product. Hidden from view, they attract little interest from building users but play a vital role in protecting people from the elements, and from unhealthy indoor climates.

Proctor Air might be a modern product, but it is preserving the building’s heritage in its own way. When the weather-tight wrap and 3700 tonnes of scaffolding are finally removed from the Town Hall, the building and its users will benefit from a reliable, high performance APLR underlay.

Thanks to the selection of Proctor Air, the roof should be capable of facing Manchester’s changing weather and climate for many years to come.

About A. Proctor Group

As a 4th generation family business with a history of technical innovation and promoting good practice, A. Proctor Group has a reputation for bringing new ideas to the market.

Proctor Air is A. Proctor Group’s roofing membrane designed for the future. BBA certified, it simplifies pitched roof constructions, being both air permeable and vapour permeable. And its water holdout performance and wind uplift resistance ensure it is able to cope with more frequent extreme weather driven by climate change.

Find out more at: proctorgroup.com/products/proctor-air