Case Study: St Paul’s Cathedral Developing the Next Generation

One of the most renowned heritage applications of mastic asphalt can be found at London’s St Paul’s Cathedral - the largest Cathedral in England. With its world famous dome, it is an iconic feature of the London skyline and the masterpiece of Britain’s most famous architect Sir Christopher Wren.

Mastic asphalt was first laid in 1906 on the Stone Gallery that circles the Cathedral dome and it provided a remarkable 111 years’ weatherproof protection before it required refurbishment by MAC contractor member Sussex Asphalte.

This project was deemed so successful that it won the accolade of Project of the Year at the MAC Annual Awards in 2018. Earlier that year, Sussex Asphalte and IKO PLC celebrated another award win with St Paul’s Cathedral as it was selected as the Best Mastic Asphalt Project at the NFRC (National Federation of Roofing Contractors) Annual Awards.

When the mastic asphalt on the Stone Gallery was renewed, approximately 20 tonnes of the original mastic asphalt was saved and stored on-site to allow it to be re-used again in the future. Just nine months later it was re-melted, sieved and used again by Sussex Asphalte for a further mastic asphalt waterproofing project at St Paul’s Cathedral - this time on the North Courtyard. The underlying workshops and storage facilities were affected by water ingress, so it was necessary to waterproof the 500m2 area, again with mastic asphalt.

The recycled mastic asphalt was used as the first layer of waterproofing to the North Courtyard. This then had a 15mm recreational duty top coat of mastic asphalt with added granite applied. The intricate nature of the courtyard with numerous protrusions, lights, changes in height and directions created a challenge to ensure all falls were adequate and no ponded water, as this is a busy storage yard for the Cathedral. There were many tight, intricate areas with changes in direction to upstands. Furthermore, the existing asphalt was difficult to remove and the awkward nature of the space made it challenging to ensure straight lines and high quality workmanship.

Where previous design details were not adequate, Sussex Asphalte - in conjunction with the Clerk of Works at St Paul’s Cathedralraised upstand heights and improved falls to ensure there was no ponding. All three of Sussex Asphalte’s current mastic asphalt apprentices who attend New City College Hackney gained vital knowledge and skills on this landmark project, under the watchful eye of Sussex Asphalte’s senior charge hand who himself attended New City College Hackney some 15 years ago through Sussex Asphalte.

The project was carried out during the lead-up to the busy Christmas period and operatives had to contend with adverse weather and plummeting temperatures, maintaining watertight areas at all times to enable works to continue below unhindered. Disruption was kept to an absolute minimum as thousands of visitors from all around the world visit the Cathedral every week. Despite the testing weather conditions and busy nature of the site, the project was delivered a week early with a saving of £11,000 for the client.

The Mastic Asphalt Council carries out a great deal of work to raise awareness amongst the younger generation about the benefits of learning to apply mastic asphalt and the career opportunities available.

As one of the few construction activities still regarded as a ‘craft trade’, it’s important that the next generation of mastic asphalt installers are developed and trained.

New City College Hackney, formerly Hackney Community College, is the national centre for mastic asphalt education and training, and relies upon support from MAC and its members.

The mastic asphalt craft is taught by professional tutors and the traditional time-served apprenticeship is now incorporated into national vocational qualifications, leading to a NVQ Level 2 or Level 3 qualification.

MAC aims to protect the future of the industry by supporting apprentices through an intensive three year training programme that will ensure they can install mastic asphalt to the highest standards. The craft training programme is said to be one of the most demanding in the construction industry, and includes practical and theoretical training to use mastic asphalt across a wide range of applications. Students can utilise state-of-the-art facilities at New City College Hackney, which include a workshop replicating a real work site and a one-tonne asphalt mixer. Several MAC members have donated plant and raw materials from which apprentices can learn the practical elements of this age-old trade.