Due to its longevity and waterproofing reliability, mastic asphalt is often selected as the ideal roof refurbishment system for museums and other buildings which house valuable collections and objects.

Mastic Asphalt Council (MAC) contractor members are frequently involved in prestigious roof renovation projects, such as Cardiff Asphalt who carried out an application at National Museum Cardiff after the previous mastic asphalt system provided a remarkable 109 years’ weatherproof protection before requiring a full roof refurbishment. The museum houses three million objects across art, archaeology and geology, as well as library and natural history collections – about half of the national collection of Wales.

One of the most recent projects has been carried out by MAC member NRA Roofing and Flooring Services Ltd at Derby Museum and Art Gallery which is home to a range of nationally important collections, including the world’s largest collection of work by the 18th Century artist Joseph Wright of Derby.

The building has a number of roofs cascading from upper to lower areas, as well as a highly unusual pitched mastic asphalt roof, adding a level of complexity to the design and installation process. It had come to the end of its serviceable life and required a complete strip out and reinstallation of a thermally improved mastic asphalt system. The client wanted the most robust and durable roofing system available as there are £70 million of paintings located in the rooms below.

NRA chose to partner with IKO as the company had the technical knowledge to assist on the complex design elements and offered the resilient, long-lasting products needed to give the client the peace of mind they were seeking. Furthermore, all areas had to achieve the client’s target u-value, whilst maintaining the integrity of the building and minimising impact on existing details.

An IKO board system was utilised as part of the mastic asphalt solution, and a new ballasted man-safe system was installed to ensure all future roof maintenance could be carried out safely. NRA finished the roof area with heritage grey paint.

The mastic asphalt application at Derby Museum and Art Gallery was considered so impressive that NRA Roofing and Flooring Services Ltd won the accolade of ‘Best Small Works Project’ at the MAC Awards hosted earlier this year.

For these projects, fire safety is often a major consideration and the high mineral content of mastic asphalt renders it virtually incombustible. Mastic asphalt fulfils all the external fire resistance required for a roof covering and achieves the highest rating (AA) when tested in accordance with BS 476: Part 3. It has also been tested in accordance with the European standard for external fire exposure to roofs CEN/TS 1187:2012. No significant spread of flame was observed and no flame penetration occurred.

As mastic asphalt is laid in molten form, it is often confused with other types of waterproofing membrane that require naked flame or torch on application. In reality, there is no naked flame at the point of installation and because mastic asphalt is so highly flame resistant, there is little or no potential of fire risk.

Mastic asphalt’s green credentials are also another benefit, as it is carbon neutral and when it has reached the end of its useful life, it can be recycled or used as roof screed. Over ten years ago the mastic asphalt sector became the first industry in the world to achieve the CarbonZero standard.

This article featured within the November 2023 edition of RCi magazine – click here to view the article.