Sustainability in Flat Roofing: Part 2

Following last month’s article on sustainability in flat roofing, SIG Design & Technology illustrate key points of the article with five case studies

In association with


Case Study One
Project: The Warrens Medical Centre, West Wirral
Architect: BRP Architects
Product: FDT Rhenofol CG with sedum roof

Specified by BRP Architects, a Rhenofol CG sedum green roof has helped The Warrens Medical Centre in West Wirral win a silver Green Apple sustainability award. Designed to achieve a BREEAM Excellent rating, the curving two-storey building is partly buried into its site and features a range of local materials, including natural stone, green oak cladding and three species of sedum.

SIG Design & Technology designed and supplied the building’s two green roofs, which cover more than 1,080 square metres. The rear roof, which incorporates photovoltaic panels and mechanical plant, has been waterproofed using Rhenofol CG. Surface water run-off is through the green roof with permeable paving systems contributing to the SUDS drainage solution.


The Warrens Medical Centre, West Wirral, by BRP Architects (phs: BRP)

Suitable for green roofing projects, Rhenofol CG is designed to resist weathering, chemical oxidation and UV radiation while retaining its physical properties over a wide range of temperatures. Its polyester fleece backing can be bonded or loose-laid when ballasted.


5 Broadgate, City of London, by Make Architects (phs: Hayes Davidson, Make Architects) 

Case Study Two
Project: 5 Broadgate, City of London
Architect: Make Architects
Product: IKO PermaTEC hot melt

Designed by Make Architects, 5 Broadgate comprises more than 65,000 square metres of office space over 12 floors in the City of London. The building’s highly challenging and technical roofscape required a waterproof layer that could perform for a minimum of 30 years, be cost-effective and contribute towards a design stage BREEAM Excellent rating.

After considering a number of options, including a warm roof and a cold applied liquid system, the project team specified an inverted roof with IKO PermaTEC hot melt. The system was favoured for its speed of installation, ease of protection, long lifespan and cost-effectiveness. Equally important were IKO PermaTEC hot melt’s environmental benefits. First and foremost, it is manufactured in the UK, and therefore ensures efficient carbon delivery miles. Second, it is produced with zero wrapper waste. This not only reduces on-site waste, but also contributes to developer British Land’s ‘Zero Waste to Landfill’ commitment and the project’s BREEAM Excellent design stage rating.


The waterproofing forms part of a 600mm roof over-cladding build-up comprising a 200mm concrete slab, a 7.5mm hot-melt rubberised bitumen membrane, a 200mm thermal extruded insulation and drainage mat, and a 150mm floating slab. Installation began with an independently monitored peel test before the rest of the application went ahead. First, ‘latents’ were ground off and the area cleaned and primed before the hot melt was applied. The waterproofing’s bonding was tested after 24 hours to check that it could withstand an attempt to peel it off.

The PermaTEC system consists of a high penetration primer, two coats of 3mm PermaTEC waterproofing membrane with a PermaFLASH-R reinforcement layer in between, and a PermaGUARD-F protection sheet. The layers were applied before the installation team began work on the next adjacent area. Unlike many cold applied liquids, with hot melt there is no need to wait until each layer hardens.


Some 15 minutes after the hot melt was applied to the roof, electronic leak testing was carried out to identify any problems and localised repairs made. This was followed by installation of an extruded polystyrene insulation board – Roofmate SL-A – then an IKO Plasdrain 6 loose-laid drainage mat. The build-up was topped by an overslab of 150mm poured concrete, with pavers and ballast used in areas of light traffic.

The finished roof achieves a U-value of 0.20, contributing to energy conservation levels that are nearly 50 per cent better than regulation standards.


Guildford Crematorium, Surrey

Case Study Three
Project: Guildford Crematorium, Surrey
Project manager: Guildford City Council
Product: FDT Rhepanol fk

When it came to replacing the copper stolen from Guildford Crematorium and Chapel of Remembrance in Surrey, the local council thought long and hard about finding a suitable replacement. “We were conscious of the fact that this is a place regularly visited by bereaved family and friends” says Guildford City Council project manager Tommy Parkes. “It was important to respect the fact that they might be sensitive to any radical changes. While it wasn’t part of the business case, we were keen to maintain the building’s aesthetic, while minimising the chance of future theft.”


To meet these objectives, the council specified a Rhepanol fk roofing membrane finished with copper paint. The latter patinated in a matter of weeks to achieve a green oxidised appearance. The membrane also satisfied the council’s environmental criteria. “Rhepanol is a synthetic rubber, whose core polymer is polyisobutylene based on Opanol – a constituent of many chewing gums”, explains SIG Design & Technology project manager Christa Coe. “Furthermore, it has a BBA-certified service life of 40 years – one of the longest available in the market, and has good natural fire protection characteristics, without resort to halogens such as bromine and chlorine.”


The council initially applied the material to back-of-house areas on the project to ascertain its suitability and to observe its patination characteristics. “Once they were convinced that it worked with the standing-seam profile attached, it was rolled out across the rest of the job”, says Coe.


Waitrose distribution centre, Aylesford

Case Study Four
Project: Waitrose Distribution Centre, Aylesford
Contractor: Genco Construction Services
Product: Spectraplan single-ply membrane

The roof of a Waitrose Distribution Centre in Aylesford, Kent, has been refurbished using 10,200 square metres of IKO’s Spectraplan single ply membrane, supplied by SIG Design & Technology. Chosen for its ability to contribute to the project’s BREEAM Very Good rating, while minimising disruption to the retailer’s 24/7 operations, the membrane was installed in only four months by approved Spectraplan installer, Genco Construction Services.

SIG Design & Technology proposed a value-engineered solution with next- day deliveries from the nearest branch of SIG Roofing Supplies to site. Employing a fast-track installation method, Genco first stripped back the existing bituminous roof, which had come to the end of its working life. After carrying out remedial works, a self-adhered vapour control layer was installed followed by 140mm insulation board and then a fully-adhered Spectraplan TPE membrane. IKO has guaranteed the new Spectraplan roofing system for 20 years on both materials and labour.


Garnet Chapel, Penkenjoch, Austria, by Mario Botta (phs: Enrico Cano)

Case Study Five
Project: Garnet Chapel, Penkenjoch
Architect: Mario Botta
Product: FDT Rhepanol fk

The crystal form of Mario Botta’s Garnet Chapel (a rhombic dodecahedron) is located in the heart of the Austrian Tyrol, overlooking the Ziller valley. Providing weather protection behind the building’s Cor-ten cladding is Rhepanol fk, a high-performance roofing membrane featuring an integrated synthetic fleece and prefabricated self-healing edge.


Among the main environmental benefits of Rhepanol fk are that it has an extremely long lifespan in use and does not contain any plasticisers or halogen fireproofing agents. An independent life cycle assessment relating to ISO EN 14040-49 showed that neither the raw materials, nor the product process or the processing and long-term use of Rhepanol fk cause any significant environmental impact. Even after its useful life the membrane can be fully recycled.

The chapel facades comprise 12 rhombus shapes made from prefabricated 120mm-thick CLT panels. To prevent wind uplift, the membranes were bonded in strips to the supporting timber structure with the permanently elastic synthetic rubber-based FDT roofing membrane adhesive. Once the initial waterproofing was carried out, threaded rods used to support the Cor-ten steel cladding were anchored in half of the elements prior to installation.


In order to achieve quick, accurate and permanent waterproof flashing against the rods, the contractor employed a preformed detail utilising a FDT lightning conductor sleeve with a Rhepanol collar. While half of the structural panels had their threaded rods fitted on the ground, the remainder where attached and waterproofed in-situ. The corners were additionally secured with special nail boards. Following this, the contractor sealed the 14 corners and 24 edges with Rhepanol cover tape and Rhepanol sealing tape – ensuring the structure was completely weatherproof and ready to receive the steel supports for the Cor-ten cladding sheets.

Contact Details

For more information on sustainability in flat roofing visit the SIG Design and Technology website.


Explore more