Existing mastic asphalt re-laid in the 1980’s was still in reasonable condition but the client established that damp within the Crypt below was the result of condensation. Rather than placing the insulation above the 40 year old Asphalt, a decision was made to renew the mastic asphalt with IKO Permaphalt which is a modern polymer modified mastic asphalt and then to install IKO enertherm XPS Insulation designed to overcome the condensation problem.
The roof was formation stepped, kept consistent with designs of the 1400’s. The stepped formation had to be levelled out with a permeable bedding prior to laying the paving slabs. Logistically this project was very challenging given the historic live environment in which the cathedral is located.
There was no direct access to the Blackadder Isle, therefore a temporary road had to be constructed leading to a working platform to house the mixer, constructed out of heavy duty railway sleepers. From here a 40m long ramp was provided to traverse the ancient graveyard and take the materials to and from the ramparts of the Isle. The asphalt was lifted up and over the parapet walls and back down to the roof area via a series of ladder hoists and pullies.
During the stripping of the existing roof covering Greenroof were advised that the Black Adder Isle housed some of the most important and priceless ornate plasterwork and cornicing in the UK. The integrity of the building could not be compromised in any way during these works.
To a bystander the site set up and processes which the environment dictated may not have looked that different to the methods some 600 years earlier.
The works, including intricate lead and stone work were completed to the standard required of Historic Environment Scotland to their absolute satisfaction.