Mastic asphalt is an integral part of our nation’s heritage, with the longevity necessary to preserve and protect many of our historical buildings – from Buckingham Palace to the Tower of London.
The Tower of London is one of the most recognisable and iconic landmarks in the capital. It is also one of the most historic, dating back almost a thousand years. A grand royal palace in its early history, it was later used as a prison, place of execution, an arsenal, royal mint, a zoo and it is currently home to the Crown Jewels – a world-famous collection of over 23,000 gemstones that are still used in royal ceremonies today.
Mastic asphalt has been relied upon as an effective waterproofing system at the Tower of London for many years. Some mastic asphalt on the Tower of London dates back to 1860 and there are many roofing areas protected with mastic asphalt that have only needed minor repairs even after 50 years.
The latest mastic asphalt application has been carried out by Mastic Asphalt Council (MAC) contractor member RJ Evans Flat Roofing on the roof of the Yeoman Keys Club – a private pub within the fortress wall.
The Tower of London is actually home to 37 Yeoman Warders, a body of men and women drawn from the British military who each must have recorded at least 22 years of active service. Nicknamed ‘Beefeaters’, they have been guarding the Tower since Tudor times and live in the Tower along with their families.
The super exclusive Yeoman Keys Club is off limits unless you are invited by a member of the Yeoman Warders. The elaborate red and gold Tudor outfits that the Beefeaters wear have changed very little over the years, but their duties have changed substantially. Originally they were charged with guarding the Tower prisoners and protecting the Crown Jewels. Today they serve more as tourist guides and are the subject of many a photo.
The Yeoman Keys Club is 150 years old and about the size of a tennis court. The roof refurbishment was carried out on behalf of English Heritage and RJ Evans Flat Roofing consulted with IKO and the Mastic Asphalt Council regarding the roofing specification. The total surface area was 220m2 excluding upstands.
The specification involved the removal of 40mm of mastic asphalt and up top 50mm of screed. All work was to be achieved without the aid of scaffold or temporary roof covering.
Once a 10mm coat of asphalt was applied to the roof in order to keep it dry, furring battens were cut to a thickness of 20mm – 60mm. A mastic asphalt screed was laid in bays to achieve a consistent fall to the channel. Thereafter, a 2 coat 20mm application of roofing grade mastic asphalt was applied to all horizontal areas and 13mm to upstands.
As all materials had to be transported over drawbridges, weight and height were a consideration. Smaller asphalt machines were used and small trucks with 1.6 tonne capacity were used 3 to 4 times per day.
Despite the challenges of the project due to its historic nature, the roof refurbishment was completed in just 14 days. RJ Evans Flat Roofing also applied mastic asphalt to Bower Wall Walk – an area of 70m2 – where it was used as waterproofing under slabs.
A liquid waterproofing system was originally considered for this project, but the rapid curing times of the mastic asphalt screeding system were particularly advantageous. Mastic asphalt screed can be laid in a matter of hours, whereas alternative screed laid to falls can take as long as 2 to 3 weeks to cure.
This article featured within the May 2022 edition of RCi Magazine – click here to view the article.