Celebrating its 150th anniversary in 2019, St. George's Weybridge – a Roman Catholic private day school in Surrey – marked the occasion with the introduction of an exciting new architectural development.
Replacing a functionally simple sports hall (a 1980s pre-fabricated building) with an inspiring, beautifully designed facility, the College’s accommodation brief comprised a premiership level hockey pitch and six-court sports hall, as well as a strength and conditioning suite, dance studio and flexible multi-use areas for group activities, meetings, presentations, exhibitions, open days and ‘match teas’.
Designed by global architectural practice Scott Brownrigg, the architect’s vision was to create a contemporary and timeless building that would inspire students to achieve their very best. The client also felt it was important to have an inspirational building as children really respond to their surroundings. They wanted them to sit up and think ‘this is a great space and I can do great things here’.
A key part of achieving this vision was the building’s roof; a stunning tree canopy-like structure that drapes over the internal spaces. The roof needed to achieve 30m clear spans across the main hall and the design needed to be clever and sensitive to the fact that the site’s location sits within the green belt on the College’s Grade II listed park. It also required a flexible and durable waterproofing solution to ensure the building leaves a lasting legacy for future generations of Georgians.
Main contractor Blenheim House Construction hired us to carry out the roofing works, which we started in October 2018 and completed in March 2019, spending a combined total of 12 weeks on.
The new 4,000 sq. m three-storey activity centre’s total project value is £15m.
The project’s architect designed a bespoke freeform glulam roof that curves in multiple directions. Computer modelling software allowed them to create and control this complex roof form in virtual reality, pushing and pulling it. The result was a gentle wave-like form that blends into the landscape.
The design needed a roofing product elegant and pliable enough to accommodate its complexities, lightweight enough to minimise the impact on the roof’s structure and cost effective enough to cover such a large area. Due to the Cross Laminated Timber (CLT) deck construction and the architect not wanting fixings penetrating through the deck, a fully adhered system was proposed by Sika Sarnafil.
Sarnafil worked closely with us, the architects and the main contractor to develop a specification that not only had the correct U-values, but was also compatible with the CLT roof build up and ancillary roof mounted systems used, such as Photovoltaics, Latchways, a built-in gutter and upstands for roof openings.
Sarnafil G410-ELF lead grey single ply membrane was specified, along with Sarnavap 5000E SA, 120m SarnaTherm G insulation board and Sika SolarMount-1. Sarnafil adhered décor profiles were built, allowing rainfall to be interrupted and guided across the roof, while Sarnavap HD SA was used in lieu of the Sarnavap 5000E on the high-pitched areas.
As we are a longstanding and experienced Sarnafil installer, and Scott Brownrigg is a regular specifier of Sarnafil, the entire team was confident that Sarnafil single ply was the right fit for this unique roof form.
In terms of installation, Sarnafil Primer 600 was the first product to go down, followed by a VCL Sarnavap HD self-adhered. 120mm Thick Sarnatherm G Insulation Boards were then adhered to the VCL with Sika C250 Spray Adhesive, and the fleece-backed membrane Sarnafil G410-15ELF Lead Grey was adhered to the insulation boards with Sarnacol 2172 adhesive. The roof perimeter had a gutter with reduced insulation thickness.
Décor Profiles were also heat welded to the roof membrane to the architect’s layout, which as well as interrupting and guiding rainwater across the roof, assist with holding snow on the steeper sections of roof.
We also installed approximately 700Lm of Sika Walkway-20 (heat welded to the roof membrane) which follows the Latchways Mansafe System and allows access to the roof area for maintenance. The Latchways Mansafe System was in our scope of works, however we couldn’t penetrate though the CLT deck and therefore had to devise a different fixing method to the standard. The final item in our scope was the supply and installation of the PV system using Sika Solar Mount system, which again was heat welded to the Sarnafil roof membrane.We ensured quality was maintained throughout the project by putting our best teams on site. Due to the visual nature of the roof, it had to be done right with real attention to detail. We also ensured there was close communication with Blenheim House Construction’s design team and Sarnafil throughout the process and worked with Tyrrell & Jenkins Consultancy Ltd to carry out electronic integrity testing on the roof during and on completion of works. Non-destructive electronic testing equipment was used - the high voltage (dry) test method. To complement the electronic testing, the integrity of the laps/seams in the waterproofing were also physically tested.
Exceptional architectural design, impeccable installation from our team and Sika Sarnafil’s robust guarantees all combined on this project to ensure this timeless building will be protected and enjoyed for years to come. A building that is cherished is more sustainable as it will last generations, rather than being knocked down and rebuilt in 20 years’ time, creating waste and emissions.
Please see our YouTube channel for a walk over this stunning roof https://www.youtube.com/watch?v=ALQwofwzvwA