Working towards zero avoidable waste in roofing

Sussex Asphalte recycled some of the asphalt on the refurbishment of St Paul’s Cathedral
Sussex Asphalte recycled some of the asphalt on the refurbishment of St Paul’s Cathedral

Malcolm Grinstead, director of the Mastic Asphalt Council, talks to RCI about reducing wasted products in roofing, and how it was achieved when renovating one of London’s oldest landmarks.

The government’s resources and waste strategy as outlined in ‘Our Waste, Our Resources: A Strategy for England (2018)’ sets out how the government plans to eliminate avoidable waste of all kinds by 2050.

The goal is to reduce the amount of waste society creates and recover and regenerate products and materials whenever we can, giving them a new lease of life.

Recycling rates in construction have improved since 2000, but rates have plateaued since 2013. Construction is one of five key areas identified by the government to prioritise in terms of minimising waste.

Constructing, maintaining, and repairing our built environment – homes, schools, offices, hospitals, and infrastructure – represents a major material resource flow in the economy. Such material flows inevitably create waste, with the construction, excavation and demolition sector estimated to have produced around 120 million tonnes in 2014 in the UK.

NFRC Guidance Note (GN33)
At every stage of the construction process, there are opportunities to reduce waste and reuse or recycle. The National Federation of Roofing Contractors (NFRC) has produced a guidance note entitled: ‘Working Towards Zero Avoidable Waste in the Roofing Sector’.

This Guidance Note (GN33) examines what the roofing sector is currently doing to avoid unnecessary waste, and how it can work over the next 30 years to ensure it has Zero Avoidable Waste (ZAW) across the roofing industry.

So, what does ZAW in construction mean? ZAW prevents any unnecessary waste from being generated at every stage of a project’s lifecycle – from the manufacture of materials and products, the design, specification, procurement, and the assembly of roof coverings, through to their removal at the end of their life.

As stated in Guidance Note (GN33), for roofs on new buildings, the focus should be on waste prevention throughout the lifecycle. This includes designing the roof to be adaptable, durable, and capable of being repurposed or deconstructed for reuse.

Reuse and recycle
For existing roofs, the focus should be on the recovery of materials and products, if the life of the roof cannot be extended or retrofitted. Examples include the remanufacture of materials for further use.

One of the main principles of circular economy, is for materials to be maintained at their highest value and to avoid downcycling.

St Paul’s Cathedral case study
A refurbishment project carried out by Mastic Asphalt Council (MAC) contractor member, Sussex Asphalte, has been featured in GN33 as an example for reusing and recycling roofing materials.

Sussex Asphalte recycled over 100-year-old asphalt salvaged from a previous project to renew the North Courtyard, which had started leaking water into the Cathedral’s workshops and storage facilities below. By recycling the asphalt, the team also saved St Paul’s over £11,000.

Mastic asphalt was first laid in 1906 on the Stone Gallery that circles the Cathedral dome, and it provided 111 years’ weatherproof protection before it required refurbishment.

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 on the Cathedral’s 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 topcoat of mastic asphalt with added granite applied. The tight, intricate nature of the courtyard with numerous protrusions, lights, upstands, changes in height and directions, created a challenge to ensure all falls were adequate, and that there was no ponded water, as this is a busy storage yard for the Cathedral. 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 Cathedral – raised 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.