London is graced with many architectural treasures from St Paul’s Cathedral to Buckingham Palace and our desire to cherish and preserve these historic buildings has become firmly established as part of our national character.  Authentic materials for the conservation of these assets must not only retain the character, but also be long lasting and highly effective.  Mastic asphalt, whilst a traditional waterproofing material, has durability and wear resistance far beyond any modern alternative which is why it is so frequently specified for refurbishment projects by the National Trust and English Heritage, as well as other public and private owners of prestigious buildings.


    Testament to the longevity of mastic asphalt, Britain’s most famous home, Buckingham Palace, features mastic asphalt on its rooftop while the Houses of Parliament’s complex and elegant roofs have also been waterproofed by the reliable material.  A modern high performance 25mm polymer modified asphalt was chosen for the detailed replacement work at St Paul’s Cathedral, meaning that it should last even longer than the previous century-old asphalt cover.


    Mastic asphalt’s heritage and performance properties are so appealing that it has recently been used to reconstruct the carriageways and walkways on the iconic 123 year old Tower Bridge, the Grade I listed river gateway into London.  In a project where only the finest materials were acceptable, the existing mastic asphalt had been in-situ for the past 30 years, keeping the mechanics of the bridge dry and protected. It was decided that the old mastic asphalt had performed so well that this hard, durable and long lasting material would be used in the refurbishment. 


    One of the biggest challenges for O’Rourke Contracting was to strip back the existing mastic asphalt and replace it on the pedestrian walkways, whilst minimising disruption to the pedestrians and river traffic. With the refurbishment carried out while the bridge was still open to pedestrians and ships, the contractor had many restrictions with plant and machinery due to weight limits. They had to break-out and reinstate 800 tons of material in total, all with limited access whilst at the same time ensuring millions of pounds worth of bridge lifting machinery was kept dry and safe.   All works to the challenging curved upstand details on the piers and the infilling of 264 original brass insert covers on the piers had to be completed to ensure no damage was caused.  With 15 different levels of mastic asphalt waterproofing on each pier laid up to a thickness of 160mm, accuracy was also key, but despite the challenges this high-profile project was completed to an exceptionally high standard, one week ahead of schedule.


    What makes mastic asphalt so appealing for heritage projects, from local restorations to maintaining internationally renowned buildings, is its suitability, performance and appearance, which is in keeping with the stonework of these prestigious structures. More faithful to tradition than virtually any other system, modern polymer modified mastic asphalt is also a far more effective waterproofing material.


    Though its life expectancy has been estimated at 50 years (far longer than “built up” methods) by the respected Building Performance Group, many MAC contractors report that they are replacing asphalt roofs laid 80 to 90 years ago. Hot laid by highly qualified craftsmen to form a jointless seam, it accommodates building movements and is less likely to leak than alternative methods.


    Providing unparalleled protection for buildings, mastic asphalt is totally impervious to water, vermin and rot and highly resistant to wear and accidental damage.  It is an ideal choice for protecting our priceless buildings and is the UK’s number choice for heritage restoration, both in London and across the country.

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