A National Landscape Discovery Centre and youth hostel by JDDK Architects in the Hadrian’s Wall World Heritage Site within the Northumberland National Park. Photography by Sally Ann Norman and Kristen Mccluskie
The Sill is a National Landscape Discovery Centre and YHA hostel at Once Brewed and responds to the client Northumberland National Park Authority’s brief to create a high-quality facility to excite and inspire visitors to explore and engage with the landscape. The building features an exhibition space, learning and event spaces, a café, rural business hub, 86-bed youth hostel and a shop.
Situated in the Hadrian’s Wall World Heritage Site within the Northumberland National Park and partially covered by a Scheduled Ancient Monument, the design responds to this sensitive setting. Inspired by the geological outcrop The Great Whin Sill, the building grows from the landscape that surrounds it, appearing as another geological ripple. The Sill’s fully accessible living roof sweeps gently upwards, giving all visitors a bird’s eye vantage point across one of the UK’s most magnificent landscapes.
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The Sill has been designed on sustainable principles. A central atrium brings daylight into the heart of the building while allowing natural ventilation.
The south-facing entrance canopy provides solar shading while also supporting photovoltaics for generating electricity. Solar panels on the roof also provide hot water, while the remaining fully accessible roof space, covered with typical Whin Sill vegetation, increases biodiversity and reduces surface water run-off.
Alison Thornton-Sykes, principal architect, JDDK Architects
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Start on site September 2015
Completion June 2017
Gross internal floor area 3,070m²
Construction cost £8.8 million
Construction cost per m2 £2,866
Client Northumberland National Park Authority
Architect JDDK Architects
Landscape architect Glen Kemp
Interpretation consultant Bricht 3D
Structural engineer Patrick Parsons
M&E consultant CAD 21
Quantity surveyor Gardiner & Theobald
Project manager Gardiner & Theobald
CDM co-ordinator Gardiner & Theobald
Approved building inspector Northumberland County Council
Main contractor Sir Robert McAlpine
CAD software used Revit
Annual CO2 emissions 41 kg/m2
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Detail and specification
The design of the 3,070m2 roof was the critical element on this project, as it had to support the indigenous flora with its specific substrate requirements, while allowing public access to the roof, keeping the building watertight and presenting minimal maintenance requirements to the client.
Initial designs considered several different roof constructions, but the main exhibition area required 16m-plus spans, which meant the only option here was a 500mm-deep reinforced concrete deck, with the rest of the more cellular structures covered with a metal composite concrete deck.
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After reviewing the available options for waterproofing the roof, initially a liquid applied solution was considered, however when looking at the maintenance required to fix any potential leak, this idea was discarded as moving 600 tonnes of topsoil and insulation would be too difficult. The solution was to use the only element common to all the different construction methods – concrete. Adding Xypex to the mix was the ideal solution, as the entire structure should remain waterproof for the lifetime of the building and its self-repairing properties reduce maintenance of the structure and waterproofing to virtually zero.
By using this additive we also managed to overcome difficult roof-wall junctions to the basement, where the building goes underground and to eliminate additional drainage to the retaining walls.
Matthew Holmes, associate director, JDDK Architects
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Xypex. XYPEX ADMIX C-1000 NF. Roof deck and retaining walls
Roof drainage layer
ABG. Roof Drain 40 and Deck Drain 2500 S. Beneath green roof
Sundolitt. XPS and XPS upstand. Beneath green roof