The Versatile Building Solution

Case Study: Wolfson College

Founded in the 1960’s, Wolfson College is one of the University of Oxford’s largest graduate colleges located in the north of the historic city. Named in honour of Sir Isaac Wolfson who contributed to the college’s foundation, the college buildings were designed by architects Powell and Moya and were ready for occupation in 1974.

Overlooking the River Cherwell, the college has three Modernist quadrangles and was awarded Grade II-listed status in 2011. Over the last few years, the college had experienced problematic leaking within the building that could have impacted on many of the rooms underneath that form the core of the establishment. These include the boiler house, workshops, nurseries, the car park and also the main switch room which controls the entire college.

MAC member Oxford Asphalt has maintained the college roofs for many years and has a long-standing relationship with the maintenance team at Wolfson College. The maintenance team sought further advice from Oxford Asphalt and a site visit was arranged with MAC Director Malcolm Grinstead, roofing manufacturer IKO and Oxford Asphalt to carry out investigations and devise a suitable waterproofing solution.

The roof area in question had originally been protected with a quarry tile finish, so due to the building’s Grade II listing, it was important that this was preserved in order to suit English Heritage’s stipulation. Furthermore, sustainability was a key element of this refurbishment project as the team at Wolfson College is striving to achieve a zero carbon estate by 2024, which marks the 50th anniversary of the opening of the college building. If this is achieved, it will make Wolfson College the first zero emissions higher education establishment in the UK.

Following the inspection at Wolfson College and further research, a specification was prepared, and Oxford Asphalt undertook the works to strip the tarmac, strip the quarry tiles and remove the reinforced concrete screed which was up to 180mm deep in places down to the concrete roof slab so the whole roof area could be started again from slab up.

A bituminous membrane was then applied on a coat of primer for a temporary waterproofing which then had IKO Permascreed built up in layers to create minimum falls of 1: 80 to the existing gully outlets.

IKO Permascreed is a super-strong, rapid-setting mastic asphalt waterproofing solution. It allows roofs and decks to be trafficked much sooner than traditional cement screeds and eliminates the potential for standing water, which was crucial for this project as the tile finish would not have worked if any standing water was present during the installation. IKO’s Polimar FCS liquid applied waterproofing was used over the mastic asphalt Permascreed due to height restrictions at perimeter details and to allow the quarry tile finish to be backed by a guarantee.

As the upstands were uneven, IKO Permaphalt mastic asphalt was applied onto Expanded Metal Lathing to create an even surface for the IKO Polimar to be installed over to give an aesthetically pleasing finished appearance. 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.

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.

The mastic asphalt refurbishment has reinstated the waterproofing on the college building, ensuring the underlying rooms are not at risk of water penetration for many years.

Even though mastic asphalt is one of the world’s most traditional construction materials, having been first patented in 1837, it has evolved to meet the needs of modern construction. Mastic asphalt requires skilled application which involves ensuring that asphalt is at the correct temperature, and then spreading it using traditional techniques to coat the surface. A thermoplastic material that changes shape when heated, mastic asphalt cures to form a hard, durable, finished product to suit all applications of mastic asphalt.

Different Applications

Mastic asphalt is most commonly associated with roofing applications and can be applied to form a continuous waterproof covering over flat, sloped or curved surfaces. It can be worked around pipes, roof lights and other projections to provide a completely seamless membrane. Able to be applied to most types of roof decks including concrete, timber and profile metal, it can also be used on warm roofs, cold roofs and inverted roofs and is manufactured in the UK.

Increasingly MAC contractor members are also installing mastic asphalt paving and finishes to balconies. It offers a hard-wearing surface for car parks, HGV service decks and bridge decks. Durability and versatility make it an ideal covering for areas subjected to regular foot traffic. It can be laid as the surface finish or beneath promenade tiles or paving slabs. Other typical applications include flooring projects, tanking and highway repairs.

Screeds

In recent years, there has been an influx of projects where mastic asphalt screeds have been used to provide a stable and cost-effective base for waterproofing applications. Unlike traditional cement screeds which can be slow to cure and labour intensive, there are mastic asphalt screeds on the market that cure rapidly even in inclement weather conditions and can be walked on within just 60 minutes, making them ideal for fast-track projects where other trades are waiting to get to work and the screed needs to be trafficked or overlaid quickly.

Mastic asphalt screeds have zero water content, eliminating the time taken for moisture to evaporate in traditional screeds and eradicating the risk of cement stained water penetrating into the underlying structure.

The flexibility and fast curing times of mastic asphalt screeds enable contractors to achieve precise drainage falls quickly and more efficiently, level out uneven substrates and provide a stable base for specified roofing deck system.

Laid at a minimum thickness of 10mm, the screed thickness is up to 80% less than traditional materials, making it much lighter and equally suited for both refurbishment and new build projects. For full waterproofing protection, mastic asphalt screeds can be overcoated with mastic asphalt roofing systems, as well as other roofing systems such as felt, hot melt roofing, liquid coatings and single ply roofing.