MAC-RCi-Nov-2022-2Mastic asphalt is most commonly associated with flat roofing applications, but due to its waterproofing properties and durability, it is also being increasingly used for the protection of terraces and walkways.
Mastic Asphalt Council (MAC) member Impact Roofing and Building has recently been involved in an impressive social housing project in London which was carried out for Clarion Housing on behalf of Wates. Clarion Housing is the UK’s largest housing association, owning and managing 125,000 homes.

Wates has partnered with Clarion Housing Group on a 20-year planned maintenance programme which began in 2019. Works carried out under the contract include kitchen and bathroom replacement, boiler replacement, window installations, rewiring and roofing to over 19,000 properties across London.

In the project undertaken by Impact Roofing and Building, mastic asphalt was used for the refurbishment of a residential block in Ollerton Green, East London, consisting of 33 flats. Four layers of asphalt had previously been applied to the walkway areas, and the asphalt had also been overlaid with a coating. The asphalt was believed to date back to as long ago as 1967 when the accommodation block was first built, so it had provided over 50 years’ protection but had deteriorated over time.

MAC-RCi-Nov-2022-3Mastic asphalt was specified for application to the entire 110 metre long, 3.5 metre wide walkway including the raised front terrace areas, all details and a large skirting to the outside wall.

A liquid waterproofing system was initially considered for the refurbishment work, but as it was necessary to completely remove the existing walkway back to a flat concrete deck, liquid wasn’t deemed to be the best option to gain new falls. Liquid would have simply followed the falls of the concrete deck and water may have ponded, thereby causing a safety hazard for residents.

The primary reason why mastic asphalt was eventually chosen was due to its exceptional durability, hard-wearing nature and the fact that it could be effectively and rapidly applied over the long walkway area, allowing the applicators to create the correct falls to the outlets, and ensuring that rainwater would flow away correctly.

The refurbishment works had to carefully programmed in with residents every day to ensure their safety and minimise disruption as much as possible. Impact Roofing and Building worked on certain sections of the walkway at given times to allow residents access to their homes.

The rapid setting nature and quick installation of mastic asphalt was a major advantage for this project, as it ensured that there were less waiting times for residents to come and go from their homes. Safety was of utmost importance, and the fact that mastic asphalt releases no hazardous or strong fumes during application was an important consideration.

Carried out over a four-week period, a surface area of 450m2 was protected with mastic asphalt. The four defective asphalt layers were removed before the application of two coats of IKO Permaphalt installed on IKO black sheathing felt.

IKO Permaphalt is a specially formulated mastic asphalt solution for waterproofing that uses advanced polymer technology to provide long term durability, increased fatigue resistance, improved temperature stability and ease of installation. A solar reflective coating was applied to the large skirting to stop it sinking in the heat.

Mastic asphalt is manufactured in the UK and when laid to a 25mm thickness, as manufactured by MAC’s manufacturing members, it achieves a reaction to fire classification of Bfl-S1 when tested in accordance with EN 13501-1:2018.

Mastic asphalt was taken to site by two x 12 tonne hot charge transporters direct from the manufacturer and taken to the point where it is needed for rapid installation – a major advantage for contracts with critical time constraints.

The client was said to be delighted with this cost-effective, well-installed solution which caused minimal disruption to residents and will provide many years of waterproof protection. Impact Roofing and Building provided a 20 year guarantee for the work.

This article featured within the November 2022 edition of RCi magazine – click here to view the article.