December 2018

Mastic Asphalt
ingress was starting to affect the structure.
Due to the outstanding performance of mastic
asphalt over the years, mastic asphalt was again
specified for the roof refurbishment involving a
5,000m² application of a polymer-modified
mastic asphalt system manufactured and
installed by MAC members IKO and Infallible
Systems respectively. Throughout the six month
project, there was very close consultation
between all parties – English Heritage, main
contractor Heritage Building and Conservation
(South), roofing specialist Infallible Systems, and
IKO – from initial specification to final sign-off to
ensure like-for-like replacements of the original
materials. Plans had to be continually adjusted at
short notice as variations in the materials and
details were uncovered.
“Weather conditions
were also a constant
obstacle to the
progress and
completion of the
works”
Challenging factors
This was a challenging project due to a number of
factors, the most significant of which was the
logistics. The castle is located in a unique
location whereby access was limited to ferries,
and by pedestrians via a 1.5 mile gravel spit.
Materials and waste had to be transported by
tractor along the spit and then lifted on and off
the roof by telehandler – including three twotonne
asphalt ‘cookers’, which were used to
prepare the mastic asphalt. Everyone working onsite
had to take the 20-minute ferry crossing to
and from the castle, meaning work was more
susceptible to delays than usual as a result of the
often choppy conditions of the Solent.
Due to the exposed nature of the site, weather
conditions were also a constant obstacle to the
progress and completion of the works. As the
refurbishment was carried out over a six month
period, the weather fluctuated between hot
sunshine and storms, with the applicators
battling wind, rain and hail. Furthermore, the
castle remained open to visitors throughout the
project, adding an extra planning element to the
safe execution of the project.
The work on the refurbishment project included
significant mastic asphalt repairs throughout the
west wing’s roof, while the roof on the east wing
was completely stripped, then laid with 150
tonnes of sand and cement screed under 300
tonnes of mastic asphalt. Concrete repairs were
also made to some structural cracks on the east
wing. The only part of the roof that wasn’t worked
on was the original Henry VIII round tower.
The majority of the work was carried out on a
significant fall from 10%-20% on the gun
emplacements and there was a great deal of
asphalt detailing required involving upstands,
downstands, vertical areas, capping, drips and
gutters. Mastic asphalt offers completely
seamless waterproofing with long-term durability
and stability across a wide temperature range. Its
ease of installation and versatility are perfectly
suited to complex, hand-laid projects, making it
ideal for the detailing the Infallible Systems team
had to carry out.
The mastic asphalt system used for this project is
backed by British Board of Agrément (BBA)
certification, with fire performance standards in
compliance with BS 476: Part 3: FAA. Mastic
asphalt is carbon neutral and 10 years ago the
mastic asphalt sector became the first industry in
the world to achieve the CarbonZero standard.
Mastic asphalt is 100% recyclable at the end of
its useful life and it is able to be recycled and
broken down into hardcore or used in roof
screeds. It reduces carbon emissions and its
seamless nature means it can be easily spot
repaired, eliminating the need for costly
wholesale replacement. A single-point insurancebacked
guarantee covering materials,
workmanship and design for up to 20 years was
provided for this project.
Regardless of the extreme weather conditions,
limited access and the very busy nature of the
site, the refurbishment work was carried out
using mastic asphalt safely, on time and to a very
high standard, to the delight of all parties
concerned. The application has allowed the roof
of this stunning fortress to be restored to its
former glory whilst ensuring effective
weatherproof protection for many years to come.
Contact The Mastic Asphalt Council
01273 242 778
www.masticasphaltcouncil.co.uk
@MasticAsphalt
44 TC DECEMBER 2018