StructureCare News

Over-Coating Mastic Asphalt - Getting It Right First Time

As the UK's leading multi-storey and rooftop car park renovation specialists, StructureCare are frequently asked to inspect and advise upon mastic asphalt wearing surfaces. These surfaces of course vary in terms of their condition and this will ultimately determine whether over-coating with a lightweight proprietary waterproof paint is feasible.

Image showing rucked asphalt due to incompatible deck coating


Over-coating mastic asphalt presents a very different set of challenges to the more common concrete substrate, and it is important to remember that many liquid applied coatings may NOT be compatible and may even have a detrimental effect on the asphalt itself.


The Eastgate Centre in Gloucester, currently being refurbished by USL StructureCare, represents an excellent example of a current asphalt over-coating project, and one which demonstrates USL's leading position in this niche market sector.


 Waterproof Coating


Image above of Eastgate Centre before works commenced


Initially, USL liaised closely with BASF, one of the worlds largest construction chemical businesses, and together the two companies prepared a detailed and bespoke specification on behalf of the client based on the EN 1504 accredited Masterseal Traffic 2205 system. Having secured the project after a competitive tender process, USL then took possession of the site in March 2016.


With isolated areas of the asphalt being in poor condition (e.g. cracking, blistering and tyre indentations), patch repairs were required to render the substrate suitable for over-coating. A critical stage of the project saw the numerous tyre indentations 'levelled' using a suitable and asphalt-compatible repair compound, which, when utilised alongside surface preparation works, leaves the substrate level and far more uniform in readiness for the lightweight waterproofing.


 Waterproof Coating


Image above shows tyre indentation repairs


On a phase by phase basis, the USL operational team then began to install the Masterseal Traffic 2205 system, beginning with the Mastertop P660 primer which is broadcast with a filler aggregate to leave a light even cover. This step of the installation process also allows any significant dimpled/crimped areas of asphalt to be significantly reduced.


 Image of primed deck


Once the primer has fully cured, the high performing, crack bridging and spray applied Masterseal M800 waterproof membrane is installed, to leave a completely watertight and highly flexible layer. The membrane is also spray applied to all details ensuring a homogenous and monolithic finish is achieved. Once cured, an M880 wearing course is then applied including a further broadcast of aggregate, and finally top coat TC681 is applied as the final finish coat.


At Gloucester, the TC681 top coat is being applied in contrasting grey colours to create the 'pad' effect. The 'pad' layout, made popular by Q-Park, provides a very professional looking car park surface, and avoids the use of white lines to define parking bays. As well as eliminating the use of white lines (which can often be an on-going maintenance item), vehicles park on the pads themselves, meaning any oil/fuel stains are masked by the dark grey deck coating.


Waterproof paint


 Images above of finished deck with waterproof paint at Eastgate Centre


Of course, many clients opt for the introduction of bright and vibrant colours as part of their car park refurbishment project, and USL have experience of numerous colour combinations. However, the most important consideration before embarking on your asphalt over-coating project is to ensure that the coating being considered is fully compatible with the asphalt, can demonstrate a decent track record and is accompanied by a meaningful and robust materials and workmanship guarantee.

For more information please email