esigned by architect practice, Morgan 2 Hayman, for developer JR Smart, the speculative office building adds to the existing 200,000ft² of office space already occupied at Capital Quarter, providing high-calibre accommodation for occupiers including Finance Wales, Alert Logic, WSP-Parsons Brinckerhoff, Network Rail, Home Office, Public Health Wales, Opus Energy, Atkins Global and Lambert Smith Hampton.
Prestige and performance
Conveniently located close to Cardiff’s railway stations and within easy reach of both the city centre and Cardiff Bay, Number Three Capital Quarter is part of a major investment in the city’s Central Business District. The specification of the office building not only needs to reflect the prestige and quality required to attract occupiers today but also needs to withstand the test of time to provide an extended service life for continued high-calibre accommodation in the future.
As a critical element of the building envelope, the roof build-up had to be aligned to this specification philosophy and the decision to use a RubberGard EPDM membrane from Firestone was driven by the developer.
Explains Gary Foster from JR Smart: “We had used Firestone’s RubberGard EPDM membrane on previous schemes on the Capital Quarter development and had been very pleased with how quickly and easily it could be installed with a neat finish.
“The service life of the roof is very important for these high-calibre office schemes as it will reduce maintenance requirements and ensure the building retains its Grade A performance. We’re confident the strength and durability of RubberGard EPDM will give us a ‘fit and forget’ solution, which – as the membrane will be obscured by the paved overlay – was a vital factor in the specification.”
The RubberGard EPDM membrane has been installed by Firestone-licensed contractor, Envirotek, on the main roof area at seventh-floor level along with the terraces at sixth- and first-floor level. The contractor was involved in the project at the design stage to ensure that sufficient provision was made for drainage in terms of the number and size of drainage outlets to maximise roof performance and avoid any risk of standing water.
Envirotek began the installation by priming the concrete roof with a bonded vapour control layer. To further aid drainage to the outlets designed into the roof, a tapered insulation scheme was then installed, creating a fall to the drainage points. This was installed as a two-layer insulation system, with flat insulation board followed by the tapered board to deliver the required U-value.
With the insulation in place, the RubberGard EPDM could be adhered to the roof. Firestone worked with Envirotek to develop the specification for the membrane, assisting with wind loading calculations and optimisation of the membrane material to support a safe installation process with high standards of integrity for the finished roof.
Comments Neil Jones from Envirotek: “We have used RubberGard EPDM on many projects but the technical support and training provided by Firestone help to ensure that we deliver the highest standards of quality and workmanship on every scheme with a team that are confident with even the most complex of details.”
The detailing required for the fully-adhered RubberGard EPDM membrane at Number Three Capital Quarter was considerable. The Envirotek team had to interface the membrane with abseiling hooks around the perimeter of the seven-storey roof, which will be used for window cleaning purposes, along with steel columns that support maintenance gantries, structural steelwork installed on the roof to create visual shielding for rooftop plant and support steelwork for a solar PV installation.
For all the penetrations, Envirotek used Firestone’s QuickSeam FormFlash, an uncured EPDM flashing laminated to cured seam tape. The tape was used to fully-encapsulate any details and regular site visits from Firestone’s technical support team ensured that all elements of the installation were fully compliant with the manufacturer’s guidelines.
The building has been designed with a 1.3m parapet wall around the perimeter of both the main roof area and the terraces, and the roofing scheme required a solution that could be taken up and over the top of these walls with a metal capping termination.
On the main roof area, Envirotek took the insulation up the wall, followed by the fully adhered RubberGard EPDM membrane. For the terraces, the RubberGard EPDM was adhered directly onto the concrete face of the parapet wall and terminated at the top of the wall with a metal capping, before being obscured by a 50mm cement particle board, which was mechanically fixed to the internal face of the wall to provide a decorative finish, visible to any occupant standing on the terrace.
Indeed, with the installation now complete, none of the RubberGard EPDM membrane is visible. Both the roof and terrace areas have been finished with 600 x 600 x 50mm paving slabs, which have been mounted onto support pads to protect the RubberGard EPDM membrane from abrasion and aid drainage. For the terrace areas, adjustable support pads enabled the paving to be laid as a flat walking surface, level with access to the sixth- and first-floor doorways, despite the falls created by the tapered insulation.
The Number Three Capital Quarter development is now almost complete, helping to energise the commercial property landscape in Cardiff and encourage growth and investment.